What does the word biology means the

Biology is the scientific study of life.^[1][2][3] It is a natural science with a broad scope but has several unifying themes that tie it together as a single, coherent field.^[1][2][3] For instance, all organisms are made up of cells that process hereditary information encoded in genes, which can be transmitted to future generations. Another major theme is evolution, which explains the unity and diversity of life.^[1][2][3] Energy processing is also important to life as it allows organisms to move, grow, and reproduce.^[1][2][3] Finally, all organisms are able to regulate their own internal environments.^{[1][2][3][4][5]}

Biologists are able to study life at multiple levels of organization,^[1] from the molecular biology of a cell to the anatomy and physiology of plants and animals, and evolution of populations.^[1][6] Hence, there are multiple subdisciplines within biology, each defined by the nature of their research questions and the tools that they use.^[7][8][9] Like other scientists, biologists use the scientific method to make observations, pose questions, generate hypotheses, perform experiments, and form conclusions about the world around them.^[1]

Life on Earth, which emerged more than 3.7 billion years ago,^[10] is immensely diverse. Biologists have sought to study and classify the various forms of life, from prokaryotic organisms such as archaea and bacteria to eukaryotic organisms such as protists, fungi, plants, and animals. These various organisms contribute to the biodiversity of an ecosystem, where they play specialized roles in the cycling of nutrients and energy through their biophysical environment.

History

The earliest of roots of science, which included medicine, can be traced to ancient Egypt and Mesopotamia in around 3000 to 1200 BCE.^[11][12] Their contributions shaped ancient Greek natural philosophy.^{[11][12][13][14]} Ancient Greek philosophers such as Aristotle (384–322 BCE) contributed extensively to the development of biological knowledge. He explored biological causation and the diversity of life. His successor, Theophrastus, began the scientific study of plants.^[15] Scholars of the medieval Islamic world who wrote on biology included al-Jahiz (781–869), Al-Dīnawarī (828–896), who wrote on botany,^[16] and Rhazes (865–925) who wrote on anatomy and physiology. Medicine was especially well studied by Islamic scholars working in Greek philosopher traditions, while natural history drew heavily on Aristotelian thought.

Biology began to quickly develop with Anton van Leeuwenhoek’s dramatic improvement of the microscope. It was then that scholars discovered spermatozoa, bacteria, infusoria and the diversity of microscopic life. Investigations by Jan Swammerdam led to new interest in entomology and helped to develop techniques of microscopic dissection and staining.^[17] Advances in microscopy had a profound impact on biological thinking. In the early 19th century, biologists pointed to the central importance of the cell. In 1838, Schleiden and Schwann began promoting the now universal ideas that (1) the basic unit of organisms is the cell and (2) that individual cells have all the characteristics of life, although they opposed the idea that (3) all cells come from the division of other cells, continuing to support spontaneous generation. However, Robert Remak and Rudolf Virchow were able to reify the third tenet, and by the 1860s most biologists accepted all three tenets which consolidated into cell theory.^[18][19]

Meanwhile, taxonomy and classification became the focus of natural historians. Carl Linnaeus published a basic taxonomy for the natural world in 1735, and in the 1750s introduced scientific names for all his species.^[20] Georges-Louis Leclerc, Comte de Buffon, treated species as artificial categories and living forms as malleable—even suggesting the possibility of common descent.^[21]

Serious evolutionary thinking originated with the works of Jean-Baptiste Lamarck, who presented a coherent theory of evolution.^[23] The British naturalist Charles Darwin, combining the biogeographical approach of Humboldt, the uniformitarian geology of Lyell, Malthus’s writings on population growth, and his own morphological expertise and extensive natural observations, forged a more successful evolutionary theory based on natural selection; similar reasoning and evidence led Alfred Russel Wallace to independently reach the same conclusions.^[24][25]

The basis for modern genetics began with the work of Gregor Mendel in 1865.^[26] This outlined the principles of biological inheritance.^[27] However, the significance of his work was not realized until the early 20th century when evolution became a unified theory as the modern synthesis reconciled Darwinian evolution with classical genetics.^[28] In the 1940s and early 1950s, a series of experiments by Alfred Hershey and Martha Chase pointed to DNA as the component of chromosomes that held the trait-carrying units that had become known as genes. A focus on new kinds of model organisms such as viruses and bacteria, along with the discovery of the double-helical structure of DNA by James Watson and Francis Crick in 1953, marked the transition to the era of molecular genetics. From the 1950s onwards, biology has been vastly extended in the molecular domain. The genetic code was cracked by Har Gobind Khorana, Robert W. Holley and Marshall Warren Nirenberg after DNA was understood to contain codons. The Human Genome Project was launched in 1990 to map the human genome.^[29]

Chemical basis

Atoms and molecules

All organisms are made up of chemical elements;^[30] oxygen, carbon, hydrogen, and nitrogen account for most (96%) of the mass of all organisms, with calcium, phosphorus, sulfur, sodium, chlorine, and magnesium constituting essentially all the remainder. Different elements can combine to form compounds such as water, which is fundamental to life.^[30] Biochemistry is the study of chemical processes within and relating to living organisms. Molecular biology is the branch of biology that seeks to understand the molecular basis of biological activity in and between cells, including molecular synthesis, modification, mechanisms, and interactions.

Water

Life arose from the Earth’s first ocean, which formed some 3.8 billion years ago.^[31] Since then, water continues to be the most abundant molecule in every organism. Water is important to life because it is an effective solvent, capable of dissolving solutes such as sodium and chloride ions or other small molecules to form an aqueous solution. Once dissolved in water, these solutes are more likely to come in contact with one another and therefore take part in chemical reactions that sustain life.^[31] In terms of its molecular structure, water is a small polar molecule with a bent shape formed by the polar covalent bonds of two hydrogen (H) atoms to one oxygen (O) atom (H₂O).^[31] Because the O–H bonds are polar, the oxygen atom has a slight negative charge and the two hydrogen atoms have a slight positive charge.^[31] This polar property of water allows it to attract other water molecules via hydrogen bonds, which makes water cohesive.^[31] Surface tension results from the cohesive force due to the attraction between molecules at the surface of the liquid.^[31] Water is also adhesive as it is able to adhere to the surface of any polar or charged non-water molecules.^[31] Water is denser as a liquid than it is as a solid (or ice).^[31] This unique property of water allows ice to float above liquid water such as ponds, lakes, and oceans, thereby insulating the liquid below from the cold air above.^[31] Water has the capacity to absorb energy, giving it a higher specific heat capacity than other solvents such as ethanol.^[31] Thus, a large amount of energy is needed to break the hydrogen bonds between water molecules to convert liquid water into water vapor.^[31] As a molecule, water is not completely stable as each water molecule continuously dissociates into hydrogen and hydroxyl ions before reforming into a water molecule again.^[31] In pure water, the number of hydrogen ions balances (or equals) the number of hydroxyl ions, resulting in a pH that is neutral.

Organic compounds

Organic compounds are molecules that contain carbon bonded to another element such as hydrogen.^[31] With the exception of water, nearly all the molecules that make up each organism contain carbon.^[31][32] Carbon can form covalent bonds with up to four other atoms, enabling it to form diverse, large, and complex molecules.^[31][32] For example, a single carbon atom can form four single covalent bonds such as in methane, two double covalent bonds such as in carbon dioxide (CO₂), or a triple covalent bond such as in carbon monoxide (CO). Moreover, carbon can form very long chains of interconnecting carbon–carbon bonds such as octane or ring-like structures such as glucose.

The simplest form of an organic molecule is the hydrocarbon, which is a large family of organic compounds that are composed of hydrogen atoms bonded to a chain of carbon atoms. A hydrocarbon backbone can be substituted by other elements such as oxygen (O), hydrogen (H), phosphorus (P), and sulfur (S), which can change the chemical behavior of that compound.^[31] Groups of atoms that contain these elements (O-, H-, P-, and S-) and are bonded to a central carbon atom or skeleton are called functional groups.^[31] There are six prominent functional groups that can be found in organisms: amino group, carboxyl group, carbonyl group, hydroxyl group, phosphate group, and sulfhydryl group.^[31]

In 1953, the Miller-Urey experiment showed that organic compounds could be synthesized abiotically within a closed system mimicking the conditions of early Earth, thus suggesting that complex organic molecules could have arisen spontaneously in early Earth (see abiogenesis).^[33][31]

Macromolecules

Macromolecules are large molecules made up of smaller subunits or monomers.^[34] Monomers include sugars, amino acids, and nucleotides.^[35] Carbohydrates include monomers and polymers of sugars.^[36]
Lipids are the only class of macromolecules that are not made up of polymers. They include steroids, phospholipids, and fats,^[35] largely nonpolar and hydrophobic (water-repelling) substances.^[37]
Proteins are the most diverse of the macromolecules. They include enzymes, transport proteins, large signaling molecules, antibodies, and structural proteins. The basic unit (or monomer) of a protein is an amino acid.^[34] Twenty amino acids are used in proteins.^[34]
Nucleic acids are polymers of nucleotides.^[38] Their function is to store, transmit, and express hereditary information.^[35]

Cells

Cell theory states that cells are the fundamental units of life, that all living things are composed of one or more cells, and that all cells arise from preexisting cells through cell division.^[39] Most cells are very small, with diameters ranging from 1 to 100 micrometers and are therefore only visible under a light or electron microscope.^[40] There are generally two types of cells: eukaryotic cells, which contain a nucleus, and prokaryotic cells, which do not. Prokaryotes are single-celled organisms such as bacteria, whereas eukaryotes can be single-celled or multicellular. In multicellular organisms, every cell in the organism’s body is derived ultimately from a single cell in a fertilized egg.

Cell structure

Every cell is enclosed within a cell membrane that separates its cytoplasm from the extracellular space.^[41] A cell membrane consists of a lipid bilayer, including cholesterols that sit between phospholipids to maintain their fluidity at various temperatures. Cell membranes are semipermeable, allowing small molecules such as oxygen, carbon dioxide, and water to pass through while restricting the movement of larger molecules and charged particles such as ions.^[42] Cell membranes also contains membrane proteins, including integral membrane proteins that go across the membrane serving as membrane transporters, and peripheral proteins that loosely attach to the outer side of the cell membrane, acting as enzymes shaping the cell.^[43] Cell membranes are involved in various cellular processes such as cell adhesion, storing electrical energy, and cell signalling and serve as the attachment surface for several extracellular structures such as a cell wall, glycocalyx, and cytoskeleton.

Within the cytoplasm of a cell, there are many biomolecules such as proteins and nucleic acids.^[44] In addition to biomolecules, eukaryotic cells have specialized structures called organelles that have their own lipid bilayers or are spatially units.^[45] These organelles include the cell nucleus, which contains most of the cell’s DNA, or mitochondria, which generates adenosine triphosphate (ATP) to power cellular processes. Other organelles such as endoplasmic reticulum and Golgi apparatus play a role in the synthesis and packaging of proteins, respectively. Biomolecules such as proteins can be engulfed by lysosomes, another specialized organelle. Plant cells have additional organelles that distinguish them from animal cells such as a cell wall that provides support for the plant cell, chloroplasts that harvest sunlight energy to produce sugar, and vacuoles that provide storage and structural support as well as being involved in reproduction and breakdown of plant seeds.^[45] Eukaryotic cells also have cytoskeleton that is made up of microtubules, intermediate filaments, and microfilaments, all of which provide support for the cell and are involved in the movement of the cell and its organelles.^[45] In terms of their structural composition, the microtubules are made up of tubulin (e.g., α-tubulin and β-tubulin whereas intermediate filaments are made up of fibrous proteins.^[45] Microfilaments are made up of actin molecules that interact with other strands of proteins.^[45]

Metabolism

All cells require energy to sustain cellular processes. Metabolism is the set of chemical reactions in an organism. The three main purposes of metabolism are: the conversion of food to energy to run cellular processes; the conversion of food/fuel to monomer building blocks; and the elimination of metabolic wastes. These enzyme-catalyzed reactions allow organisms to grow and reproduce, maintain their structures, and respond to their environments. Metabolic reactions may be categorized as catabolic—the breaking down of compounds (for example, the breaking down of glucose to pyruvate by cellular respiration); or anabolic—the building up (synthesis) of compounds (such as proteins, carbohydrates, lipids, and nucleic acids). Usually, catabolism releases energy, and anabolism consumes energy. The chemical reactions of metabolism are organized into metabolic pathways, in which one chemical is transformed through a series of steps into another chemical, each step being facilitated by a specific enzyme. Enzymes are crucial to metabolism because they allow organisms to drive desirable reactions that require energy that will not occur by themselves, by coupling them to spontaneous reactions that release energy. Enzymes act as catalysts—they allow a reaction to proceed more rapidly without being consumed by it—by reducing the amount of activation energy needed to convert reactants into products. Enzymes also allow the regulation of the rate of a metabolic reaction, for example in response to changes in the cell’s environment or to signals from other cells.

Cellular respiration

Cellular respiration is a set of metabolic reactions and processes that take place in cells to convert chemical energy from nutrients into adenosine triphosphate (ATP), and then release waste products.^[46] The reactions involved in respiration are catabolic reactions, which break large molecules into smaller ones, releasing energy. Respiration is one of the key ways a cell releases chemical energy to fuel cellular activity. The overall reaction occurs in a series of biochemical steps, some of which are redox reactions. Although cellular respiration is technically a combustion reaction, it clearly does not resemble one when it occurs in a cell because of the slow, controlled release of energy from the series of reactions.

Sugar in the form of glucose is the main nutrient used by animal and plant cells in respiration. Cellular respiration involving oxygen is called aerobic respiration, which has four stages: glycolysis, citric acid cycle (or Krebs cycle), electron transport chain, and oxidative phosphorylation.^[47] Glycolysis is a metabolic process that occurs in the cytoplasm whereby glucose is converted into two pyruvates, with two net molecules of ATP being produced at the same time.^[47] Each pyruvate is then oxidized into acetyl-CoA by the pyruvate dehydrogenase complex, which also generates NADH and carbon dioxide. Acetyl-Coa enters the citric acid cycle, which takes places inside the mitochondrial matrix. At the end of the cycle, the total yield from 1 glucose (or 2 pyruvates) is 6 NADH, 2 FADH₂, and 2 ATP molecules. Finally, the next stage is oxidative phosphorylation, which in eukaryotes, occurs in the mitochondrial cristae. Oxidative phosphorylation comprises the electron transport chain, which is a series of four protein complexes that transfer electrons from one complex to another, thereby releasing energy from NADH and FADH₂ that is coupled to the pumping of protons (hydrogen ions) across the inner mitochondrial membrane (chemiosmosis), which generates a proton motive force.^[47] Energy from the proton motive force drives the enzyme ATP synthase to synthesize more ATPs by phosphorylating ADPs. The transfer of electrons terminates with molecular oxygen being the final electron acceptor.

If oxygen were not present, pyruvate would not be metabolized by cellular respiration but undergoes a process of fermentation. The pyruvate is not transported into the mitochondrion but remains in the cytoplasm, where it is converted to waste products that may be removed from the cell. This serves the purpose of oxidizing the electron carriers so that they can perform glycolysis again and removing the excess pyruvate. Fermentation oxidizes NADH to NAD⁺ so it can be re-used in glycolysis. In the absence of oxygen, fermentation prevents the buildup of NADH in the cytoplasm and provides NAD⁺ for glycolysis. This waste product varies depending on the organism. In skeletal muscles, the waste product is lactic acid. This type of fermentation is called lactic acid fermentation. In strenuous exercise, when energy demands exceed energy supply, the respiratory chain cannot process all of the hydrogen atoms joined by NADH. During anaerobic glycolysis, NAD⁺ regenerates when pairs of hydrogen combine with pyruvate to form lactate. Lactate formation is catalyzed by lactate dehydrogenase in a reversible reaction. Lactate can also be used as an indirect precursor for liver glycogen. During recovery, when oxygen becomes available, NAD⁺ attaches to hydrogen from lactate to form ATP. In yeast, the waste products are ethanol and carbon dioxide. This type of fermentation is known as alcoholic or ethanol fermentation. The ATP generated in this process is made by substrate-level phosphorylation, which does not require oxygen.

Photosynthesis

Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that can later be released to fuel the organism’s metabolic activities via cellular respiration. This chemical energy is stored in carbohydrate molecules, such as sugars, which are synthesized from carbon dioxide and water.^[48][49][50] In most cases, oxygen is released as a waste product. Most plants, algae, and cyanobacteria perform photosynthesis, which is largely responsible for producing and maintaining the oxygen content of the Earth’s atmosphere, and supplies most of the energy necessary for life on Earth.^[51]

Photosynthesis has four stages: Light absorption, electron transport, ATP synthesis, and carbon fixation.^[47] Light absorption is the initial step of photosynthesis whereby light energy is absorbed by chlorophyll pigments attached to proteins in the thylakoid membranes. The absorbed light energy is used to remove electrons from a donor (water) to a primary electron acceptor, a quinone designated as Q. In the second stage, electrons move from the quinone primary electron acceptor through a series of electron carriers until they reach a final electron acceptor, which is usually the oxidized form of NADP⁺, which is reduced to NADPH, a process that takes place in a protein complex called photosystem I (PSI). The transport of electrons is coupled to the movement of protons (or hydrogen) from the stroma to the thylakoid membrane, which forms a pH gradient across the membrane as hydrogen becomes more concentrated in the lumen than in the stroma. This is analogous to the proton-motive force generated across the inner mitochondrial membrane in aerobic respiration.^[47]

During the third stage of photosynthesis, the movement of protons down their concentration gradients from the thylakoid lumen to the stroma through the ATP synthase is coupled to the synthesis of ATP by that same ATP synthase.^[47] The NADPH and ATPs generated by the light-dependent reactions in the second and third stages, respectively, provide the energy and electrons to drive the synthesis of glucose by fixing atmospheric carbon dioxide into existing organic carbon compounds, such as ribulose bisphosphate (RuBP) in a sequence of light-independent (or dark) reactions called the Calvin cycle.^[52]

Cell signaling

Cell signaling (or communication) is the ability of cells to receive, process, and transmit signals with its environment and with itself.^[53][54] Signals can be non-chemical such as light, electrical impulses, and heat, or chemical signals (or ligands) that interact with receptors, which can be found embedded in the cell membrane of another cell or located deep inside a cell.^[55][54] There are generally four types of chemical signals: autocrine, paracrine, juxtacrine, and hormones.^[55] In autocrine signaling, the ligand affects the same cell that releases it. Tumor cells, for example, can reproduce uncontrollably because they release signals that initiate their own self-division. In paracrine signaling, the ligand diffuses to nearby cells and affects them. For example, brain cells called neurons release ligands called neurotransmitters that diffuse across a synaptic cleft to bind with a receptor on an adjacent cell such as another neuron or muscle cell. In juxtacrine signaling, there is direct contact between the signaling and responding cells. Finally, hormones are ligands that travel through the circulatory systems of animals or vascular systems of plants to reach their target cells. Once a ligand binds with a receptor, it can influence the behavior of another cell, depending on the type of receptor. For instance, neurotransmitters that bind with an inotropic receptor can alter the excitability of a target cell. Other types of receptors include protein kinase receptors (e.g., receptor for the hormone insulin) and G protein-coupled receptors. Activation of G protein-coupled receptors can initiate second messenger cascades. The process by which a chemical or physical signal is transmitted through a cell as a series of molecular events is called signal transduction

Cell cycle

The cell cycle is a series of events that take place in a cell that cause it to divide into two daughter cells. These events include the duplication of its DNA and some of its organelles, and the subsequent partitioning of its cytoplasm into two daughter cells in a process called cell division.^[56] In eukaryotes (i.e., animal, plant, fungal, and protist cells), there are two distinct types of cell division: mitosis and meiosis.^[57] Mitosis is part of the cell cycle, in which replicated chromosomes are separated into two new nuclei. Cell division gives rise to genetically identical cells in which the total number of chromosomes is maintained. In general, mitosis (division of the nucleus) is preceded by the S stage of interphase (during which the DNA is replicated) and is often followed by telophase and cytokinesis; which divides the cytoplasm, organelles and cell membrane of one cell into two new cells containing roughly equal shares of these cellular components. The different stages of mitosis all together define the mitotic phase of an animal cell cycle—the division of the mother cell into two genetically identical daughter cells.^[58] The cell cycle is a vital process by which a single-celled fertilized egg develops into a mature organism, as well as the process by which hair, skin, blood cells, and some internal organs are renewed. After cell division, each of the daughter cells begin the interphase of a new cycle. In contrast to mitosis, meiosis results in four haploid daughter cells by undergoing one round of DNA replication followed by two divisions.^[59] Homologous chromosomes are separated in the first division (meiosis I), and sister chromatids are separated in the second division (meiosis II). Both of these cell division cycles are used in the process of sexual reproduction at some point in their life cycle. Both are believed to be present in the last eukaryotic common ancestor.

Prokaryotes (i.e., archaea and bacteria) can also undergo cell division (or binary fission). Unlike the processes of mitosis and meiosis in eukaryotes, binary fission takes in prokaryotes takes place without the formation of a spindle apparatus on the cell. Before binary fission, DNA in the bacterium is tightly coiled. After it has uncoiled and duplicated, it is pulled to the separate poles of the bacterium as it increases the size to prepare for splitting. Growth of a new cell wall begins to separate the bacterium (triggered by FtsZ polymerization and «Z-ring» formation)^[60] The new cell wall (septum) fully develops, resulting in the complete split of the bacterium. The new daughter cells have tightly coiled DNA rods, ribosomes, and plasmids.

Genetics

Inheritance

Genetics is the scientific study of inheritance.^[61][62][63] Mendelian inheritance, specifically, is the process by which genes and traits are passed on from parents to offspring.^[27] It has several principles. The first is that genetic characteristics, alleles, are discrete and have alternate forms (e.g., purple vs. white or tall vs. dwarf), each inherited from one of two parents. Based on the law of dominance and uniformity, which states that some alleles are dominant while others are recessive; an organism with at least one dominant allele will display the phenotype of that dominant allele. During gamete formation, the alleles for each gene segregate, so that each gamete carries only one allele for each gene. Heterozygotic individuals produce gametes with an equal frequency of two alleles. Finally, the law of independent assortment, states that genes of different traits can segregate independently during the formation of gametes, i.e., genes are unlinked. An exception to this rule would include traits that are sex-linked. Test crosses can be performed to experimentally determine the underlying genotype of an organism with a dominant phenotype.^[64] A Punnett square can be used to predict the results of a test cross. The chromosome theory of inheritance, which states that genes are found on chromosomes, was supported by Thomas Morgans’s experiments with fruit flies, which established the sex linkage between eye color and sex in these insects.^[65]

Genes and DNA

Further information: Gene and DNA

A gene is a unit of heredity that corresponds to a region of deoxyribonucleic acid (DNA) that carries genetic information that controls form or function of an organism. DNA is composed of two polynucleotide chains that coil around each other to form a double helix.^[66] It is found as linear chromosomes in eukaryotes, and circular chromosomes in prokaryotes. The set of chromosomes in a cell is collectively known as its genome. In eukaryotes, DNA is mainly in the cell nucleus.^[67] In prokaryotes, the DNA is held within the nucleoid.^[68] The genetic information is held within genes, and the complete assemblage in an organism is called its genotype.^[69]
DNA replication is a semiconservative process whereby each strand serves as a template for a new strand of DNA.^[66] Mutations are heritable changes in DNA.^[66] They can arise spontaneously as a result of replication errors that were not corrected by proofreading or can be induced by an environmental mutagen such as a chemical (e.g., nitrous acid, benzopyrene) or radiation (e.g., x-ray, gamma ray, ultraviolet radiation, particles emitted by unstable isotopes).^[66] Mutations can lead to phenotypic effects such as loss-of-function, gain-of-function, and conditional mutations.^[66]
Some mutations are beneficial, as they are a source of genetic variation for evolution.^[66] Others are harmful if they were to result in a loss of function of genes needed for survival.^[66] Mutagens such as carcinogens are typically avoided as a matter of public health policy goals.^[66]

Gene expression

Gene expression is the molecular process by which a genotype encoded in DNA gives rise to an observable phenotype in the proteins of an organism’s body. This process is summarized by the central dogma of molecular biology, which was formulated by Francis Crick in 1958.^[70][71][72] According to the Central Dogma, genetic information flows from DNA to RNA to protein. There are two gene expression processes: transcription (DNA to RNA) and translation (RNA to protein).^[73]

Gene regulation

The regulation of gene expression by environmental factors and during different stages of development can occur at each step of the process such as transcription, RNA splicing, translation, and post-translational modification of a protein.^[74] Gene expression can be influenced by positive or negative regulation, depending on which of the two types of regulatory proteins called transcription factors bind to the DNA sequence close to or at a promoter.^[74] A cluster of genes that share the same promoter is called an operon, found mainly in prokaryotes and some lower eukaryotes (e.g., Caenorhabditis elegans).^[74][75] In positive regulation of gene expression, the activator is the transcription factor that stimulates transcription when it binds to the sequence near or at the promoter. Negative regulation occurs when another transcription factor called a repressor binds to a DNA sequence called an operator, which is part of an operon, to prevent transcription. Repressors can be inhibited by compounds called inducers (e.g., allolactose), thereby allowing transcription to occur.^[74] Specific genes that can be activated by inducers are called inducible genes, in contrast to constitutive genes that are almost constantly active.^[74] In contrast to both, structural genes encode proteins that are not involved in gene regulation.^[74] In addition to regulatory events involving the promoter, gene expression can also be regulated by epigenetic changes to chromatin, which is a complex of DNA and protein found in eukaryotic cells.^[74]

Genes, development, and evolution

Development is the process by which a multicellular organism (plant or animal) goes through a series of changes, starting from a single cell, and taking on various forms that are characteristic of its life cycle.^[76] There are four key processes that underlie development: Determination, differentiation, morphogenesis, and growth. Determination sets the developmental fate of a cell, which becomes more restrictive during development. Differentiation is the process by which specialized cells from less specialized cells such as stem cells.^[77][78] Stem cells are undifferentiated or partially differentiated cells that can differentiate into various types of cells and proliferate indefinitely to produce more of the same stem cell.^[79] Cellular differentiation dramatically changes a cell’s size, shape, membrane potential, metabolic activity, and responsiveness to signals, which are largely due to highly controlled modifications in gene expression and epigenetics. With a few exceptions, cellular differentiation almost never involves a change in the DNA sequence itself.^[80] Thus, different cells can have very different physical characteristics despite having the same genome. Morphogenesis, or the development of body form, is the result of spatial differences in gene expression.^[76] A small fraction of the genes in an organism’s genome called the developmental-genetic toolkit control the development of that organism. These toolkit genes are highly conserved among phyla, meaning that they are ancient and very similar in widely separated groups of animals. Differences in deployment of toolkit genes affect the body plan and the number, identity, and pattern of body parts. Among the most important toolkit genes are the Hox genes. Hox genes determine where repeating parts, such as the many vertebrae of snakes, will grow in a developing embryo or larva.^[81]

Evolution

Evolutionary processes

Evolution is a central organizing concept in biology. It is the change in heritable characteristics of populations over successive generations.^[82][83] In artificial selection, animals were selectively bred for specific traits.
^[84] Given that traits are inherited, populations contain a varied mix of traits, and reproduction is able to increase any population, Darwin argued that in the natural world, it was nature that played the role of humans in selecting for specific traits.^[84] Darwin inferred that individuals who possessed heritable traits better adapted to their environments are more likely to survive and produce more offspring than other individuals.^[84] He further inferred that this would lead to the accumulation of favorable traits over successive generations, thereby increasing the match between the organisms and their environment.^{[85][86][87][84][88]}

Speciation

A species is a group of organisms that mate with one another and speciation is the process by which one lineage splits into two lineages as a result of having evolved independently from each other.^[89] For speciation to occur, there has to be reproductive isolation.^[89] Reproductive isolation can result from incompatibilities between genes as described by Bateson–Dobzhansky–Muller model. Reproductive isolation also tends to increase with genetic divergence. Speciation can occur when there are physical barriers that divide an ancestral species, a process known as allopatric speciation.^[89]

Phylogeny

A phylogeny is an evolutionary history of a specific group of organisms or their genes.^[90] It can be represented using a phylogenetic tree, a diagram showing lines of descent among organisms or their genes. Each line drawn on the time axis of a tree represents a lineage of descendants of a particular species or population. When a lineage divides into two, it is represented as a fork or split on the phylogenetic tree.^[90] Phylogenetic trees are the basis for comparing and grouping different species.^[90] Different species that share a feature inherited from a common ancestor are described as having homologous features (or synapomorphy).^[91][92][90] Phylogeny provides the basis of biological classification.^[90] This classification system is rank-based, with the highest rank being the domain followed by kingdom, phylum, class, order, family, genus, and species.^[90] All organisms can be classified as belonging to one of three domains: Archaea (originally Archaebacteria); bacteria (originally eubacteria), or eukarya (includes the protist, fungi, plant, and animal kingdoms).^[93]

History of life

The history of life on Earth traces how organisms have evolved from the earliest emergence of life to present day. Earth formed about 4.5 billion years ago and all life on Earth, both living and extinct, descended from a last universal common ancestor that lived about 3.5 billion years ago.^[94][95] Geologists have developed a geologic time scale that divides the history of the Earth into major divisions, starting with four eons (Hadean, Archean, Proterozoic, and Phanerozoic), the first three of which are collectively known as the Precambrian, which lasted approximately 4 billion years.^[96] Each eon can be divided into eras, with the Phanerozoic eon that began 539 million years ago^[97] being subdivided into Paleozoic, Mesozoic, and Cenozoic eras.^[96] These three eras together comprise eleven periods (Cambrian, Ordovician, Silurian, Devonian, Carboniferous, Permian, Triassic, Jurassic, Cretaceous, Tertiary, and Quaternary).^[96]

The similarities among all known present-day species indicate that they have diverged through the process of evolution from their common ancestor.^[98] Biologists regard the ubiquity of the genetic code as evidence of universal common descent for all bacteria, archaea, and eukaryotes.^{[99][10][100][101]} Microbal mats of coexisting bacteria and archaea were the dominant form of life in the early Archean epoch and many of the major steps in early evolution are thought to have taken place in this environment.^[102] The earliest evidence of eukaryotes dates from 1.85 billion years ago,^[103][104] and while they may have been present earlier, their diversification accelerated when they started using oxygen in their metabolism. Later, around 1.7 billion years ago, multicellular organisms began to appear, with differentiated cells performing specialised functions.^[105]

Algae-like multicellular land plants are dated back even to about 1 billion years ago,^[106] although evidence suggests that microorganisms formed the earliest terrestrial ecosystems, at least 2.7 billion years ago.^[107] Microorganisms are thought to have paved the way for the inception of land plants in the Ordovician period. Land plants were so successful that they are thought to have contributed to the Late Devonian extinction event.^[108]

Ediacara biota appear during the Ediacaran period,^[109] while vertebrates, along with most other modern phyla originated about 525 million years ago during the Cambrian explosion.^[110] During the Permian period, synapsids, including the ancestors of mammals, dominated the land,^[111] but most of this group became extinct in the Permian–Triassic extinction event 252 million years ago.^[112] During the recovery from this catastrophe, archosaurs became the most abundant land vertebrates;^[113] one archosaur group, the dinosaurs, dominated the Jurassic and Cretaceous periods.^[114] After the Cretaceous–Paleogene extinction event 66 million years ago killed off the non-avian dinosaurs,^[115] mammals increased rapidly in size and diversity.^[116] Such mass extinctions may have accelerated evolution by providing opportunities for new groups of organisms to diversify.^[117]

Diversity

Bacteria and Archaea

Bacteria are a type of cell that constitute a large domain of prokaryotic microorganisms. Typically a few micrometers in length, bacteria have a number of shapes, ranging from spheres to rods and spirals. Bacteria were among the first life forms to appear on Earth, and are present in most of its habitats. Bacteria inhabit soil, water, acidic hot springs, radioactive waste,^[118] and the deep biosphere of the earth’s crust. Bacteria also live in symbiotic and parasitic relationships with plants and animals. Most bacteria have not been characterised, and only about 27 percent of the bacterial phyla have species that can be grown in the laboratory.^[119]

Archaea constitute the other domain of prokaryotic cells and were initially classified as bacteria, receiving the name archaebacteria (in the Archaebacteria kingdom), a term that has fallen out of use.^[120] Archaeal cells have unique properties separating them from the other two domains, Bacteria and Eukaryota. Archaea are further divided into multiple recognized phyla. Archaea and bacteria are generally similar in size and shape, although a few archaea have very different shapes, such as the flat and square cells of Haloquadratum walsbyi.^[121] Despite this morphological similarity to bacteria, archaea possess genes and several metabolic pathways that are more closely related to those of eukaryotes, notably for the enzymes involved in transcription and translation. Other aspects of archaeal biochemistry are unique, such as their reliance on ether lipids in their cell membranes,^[122] including archaeols. Archaea use more energy sources than eukaryotes: these range from organic compounds, such as sugars, to ammonia, metal ions or even hydrogen gas. Salt-tolerant archaea (the Haloarchaea) use sunlight as an energy source, and other species of archaea fix carbon, but unlike plants and cyanobacteria, no known species of archaea does both. Archaea reproduce asexually by binary fission, fragmentation, or budding; unlike bacteria, no known species of Archaea form endospores.

The first observed archaea were extremophiles, living in extreme environments, such as hot springs and salt lakes with no other organisms. Improved molecular detection tools led to the discovery of archaea in almost every habitat, including soil, oceans, and marshlands. Archaea are particularly numerous in the oceans, and the archaea in plankton may be one of the most abundant groups of organisms on the planet.

Archaea are a major part of Earth’s life. They are part of the microbiota of all organisms. In the human microbiome, they are important in the gut, mouth, and on the skin.^[123] Their morphological, metabolic, and geographical diversity permits them to play multiple ecological roles: carbon fixation; nitrogen cycling; organic compound turnover; and maintaining microbial symbiotic and syntrophic communities, for example.^[124]

Eukaryotes

Eukaryotes are hypothesized to have split from archaea, which was followed by their endosymbioses with bacteria (or symbiogenesis) that gave rise to mitochondria and chloroplasts, both of which are now part of modern-day eukaryotic cells.^[125] The major lineages of eukaryotes diversified in the Precambrian about 1.5 billion years ago and can be classified into eight major clades: alveolates, excavates, stramenopiles, plants, rhizarians, amoebozoans, fungi, and animals.^[125] Five of these clades are collectively known as protists, which are mostly microscopic eukaryotic organisms that are not plants, fungi, or animals.^[125] While it is likely that protists share a common ancestor (the last eukaryotic common ancestor),^[126] protists by themselves do not constitute a separate clade as some protists may be more closely related to plants, fungi, or animals than they are to other protists. Like groupings such as algae, invertebrates, or protozoans, the protist grouping is not a formal taxonomic group but is used for convenience.^[125][127] Most protists are unicellular; these are called microbial eukaryotes.^[125]

Plants are mainly multicellular organisms, predominantly photosynthetic eukaryotes of the kingdom Plantae, which would exclude fungi and some algae. Plant cells were derived by endosymbiosis of a cyanobacterium into an early eukaryote about one billion years ago, which gave rise to chloroplasts.^[128] The first several clades that emerged following primary endosymbiosis were aquatic and most of the aquatic photosynthetic eukaryotic organisms are collectively described as algae, which is a term of convenience as not all algae are closely related.^[128] Algae comprise several distinct clades such as glaucophytes, which are microscopic freshwater algae that may have resembled in form to the early unicellular ancestor of Plantae.^[128] Unlike glaucophytes, the other algal clades such as red and green algae are multicellular. Green algae comprise three major clades: chlorophytes, coleochaetophytes, and stoneworts.^[128]

Fungi are eukaryotes that digest foods outside their bodies,^[129] secreting digestive enzymes that break down large food molecules before absorbing them through their cell membranes. Many fungi are also saprobes, feeding on dead organic matter, making them important decomposers in ecological systems.^[129]

Animals are multicellular eukaryotes. With few exceptions, animals consume organic material, breathe oxygen, are able to move, can reproduce sexually, and grow from a hollow sphere of cells, the blastula, during embryonic development. Over 1.5 million living animal species have been described—of which around 1 million are insects—but it has been estimated there are over 7 million animal species in total. They have complex interactions with each other and their environments, forming intricate food webs.^[130]

Viruses

Viruses are submicroscopic infectious agents that replicate inside the cells of organisms.^[131] Viruses infect all types of life forms, from animals and plants to microorganisms, including bacteria and archaea.^[132][133] More than 6,000 virus species have been described in detail.^[134] Viruses are found in almost every ecosystem on Earth and are the most numerous type of biological entity.^[135][136]

The origins of viruses in the evolutionary history of life are unclear: some may have evolved from plasmids—pieces of DNA that can move between cells—while others may have evolved from bacteria. In evolution, viruses are an important means of horizontal gene transfer, which increases genetic diversity in a way analogous to sexual reproduction.^[137] Because viruses possess some but not all characteristics of life, they have been described as «organisms at the edge of life»,^[138] and as self-replicators.^[139]

Ecology

Ecology is the study of the distribution and abundance of life, the interaction between organisms and their environment.^[140]

Ecosystems

The community of living (biotic) organisms in conjunction with the nonliving (abiotic) components (e.g., water, light, radiation, temperature, humidity, atmosphere, acidity, and soil) of their environment is called an ecosystem.^{[141][142][143]} These biotic and abiotic components are linked together through nutrient cycles and energy flows.^[144] Energy from the sun enters the system through photosynthesis and is incorporated into plant tissue. By feeding on plants and on one another, animals move matter and energy through the system. They also influence the quantity of plant and microbial biomass present. By breaking down dead organic matter, decomposers release carbon back to the atmosphere and facilitate nutrient cycling by converting nutrients stored in dead biomass back to a form that can be readily used by plants and other microbes.^[145]

Populations

A population is the group of organisms of the same species that occupies an area and reproduce from generation to generation.^{[146][147][148][149][150]} Population size can be estimated by multiplying population density by the area or volume. The carrying capacity of an environment is the maximum population size of a species that can be sustained by that specific environment, given the food, habitat, water, and other resources that are available.^[151] The carrying capacity of a population can be affected by changing environmental conditions such as changes in the availability resources and the cost of maintaining them. In human populations, new technologies such as the Green revolution have helped increase the Earth’s carrying capacity for humans over time, which has stymied the attempted predictions of impending population decline, the most famous of which was by Thomas Malthus in the 18th century.^[146]

Communities

A community is a group of populations of species occupying the same geographical area at the same time. A biological interaction is the effect that a pair of organisms living together in a community have on each other. They can be either of the same species (intraspecific interactions), or of different species (interspecific interactions). These effects may be short-term, like pollination and predation, or long-term; both often strongly influence the evolution of the species involved. A long-term interaction is called a symbiosis. Symbioses range from mutualism, beneficial to both partners, to competition, harmful to both partners.^[153] Every species participates as a consumer, resource, or both in consumer–resource interactions, which form the core of food chains or food webs.^[154] There are different trophic levels within any food web, with the lowest level being the primary producers (or autotrophs) such as plants and algae that convert energy and inorganic material into organic compounds, which can then be used by the rest of the community.^{[51][155][156]} At the next level are the heterotrophs, which are the species that obtain energy by breaking apart organic compounds from other organisms.^[154] Heterotrophs that consume plants are primary consumers (or herbivores) whereas heterotrophs that consume herbivores are secondary consumers (or carnivores). And those that eat secondary consumers are tertiary consumers and so on. Omnivorous heterotrophs are able to consume at multiple levels. Finally, there are decomposers that feed on the waste products or dead bodies of organisms.^[154]
On average, the total amount of energy incorporated into the biomass of a trophic level per unit of time is about one-tenth of the energy of the trophic level that it consumes. Waste and dead material used by decomposers as well as heat lost from metabolism make up the other ninety percent of energy that is not consumed by the next trophic level.^[157]

Biosphere

In the global ecosystem or biosphere, matter exists as different interacting compartments, which can be biotic or abiotic as well as accessible or inaccessible, depending on their forms and locations.^[159] For example, matter from terrestrial autotrophs are both biotic and accessible to other organisms whereas the matter in rocks and minerals are abiotic and inaccessible. A biogeochemical cycle is a pathway by which specific elements of matter are turned over or moved through the biotic (biosphere) and the abiotic (lithosphere, atmosphere, and hydrosphere) compartments of Earth. There are biogeochemical cycles for nitrogen, carbon, and water.

Conservation

Conservation biology is the study of the conservation of Earth’s biodiversity with the aim of protecting species, their habitats, and ecosystems from excessive rates of extinction and the erosion of biotic interactions.^{[160][161][162]} It is concerned with factors that influence the maintenance, loss, and restoration of biodiversity and the science of sustaining evolutionary processes that engender genetic, population, species, and ecosystem diversity.^{[163][164][165][166]} The concern stems from estimates suggesting that up to 50% of all species on the planet will disappear within the next 50 years,^[167] which has contributed to poverty, starvation, and will reset the course of evolution on this planet.^[168][169] Biodiversity affects the functioning of ecosystems, which provide a variety of services upon which people depend. Conservation biologists research and educate on the trends of biodiversity loss, species extinctions, and the negative effect these are having on our capabilities to sustain the well-being of human society. Organizations and citizens are responding to the current biodiversity crisis through conservation action plans that direct research, monitoring, and education programs that engage concerns at local through global scales.^{[170][163][164][165]}

See also

References

Further reading

External links

• Biology at Curlie
• OSU’s Phylocode
• Biology Online – Wiki Dictionary
• MIT video lecture series on biology
• OneZoom Tree of Life

Journal links

• PLOS Biology A peer-reviewed, open-access journal published by the Public Library of Science
• Current Biology: General journal publishing original research from all areas of biology
• Biology Letters: A high-impact Royal Society journal publishing peer-reviewed biology papers of general interest
• Science: Internationally renowned AAAS science journal – see sections of the life sciences
• International Journal of Biological Sciences: A biological journal publishing significant peer-reviewed scientific papers
• Perspectives in Biology and Medicine: An interdisciplinary scholarly journal publishing essays of broad relevance

Biology is the study of life. The word «biology» is derived from the Greek words «bios» (meaning life) and «logos» (meaning «study»). In general, biologists study the structure, function, growth, origin, evolution and distribution of living organisms.

Biology is important because it helps us understand how living things work and how they function and interact on multiple levels, according to the Encyclopedia Britannica (opens in new tab). Advances in biology have helped scientists do things such as develop better medicines and treatments for diseases, understand how a changing environment might affect plants and animals, produce enough food for a growing human population and predict how eating new food or sticking to an exercise regimen might affect our bodies.

The basic principles of modern biology

Four principles unify modern biology, according to the book «Managing Science» (Springer New York, 2010): 

1. Cell theory is the principle that all living things are made of fundamental units called cells, and all cells come from preexisting cells.
2. Gene theory is the principle that all living things have DNA, molecules that code the structures and functions of cells and get passed to offspring.
3. Homeostasis is the principle that all living things maintain a state of balance that enables organisms to survive in their environment.
4. Evolution is the principle that describes how all living things can change to have traits that enable them to survive better in their environments. These traits result from random mutations in the organism’s genes that are «selected» via a process called natural selection. During natural selection, organisms that have traits better-suited for their environment have higher rates of survival, and then pass those traits to their offspring.

The many branches of biology

Although there are only four unifying principles, biology covers a broad range of topics that are broken into many disciplines and subdisciplines.

On a high level, the different fields of biology can each be thought of as the study of one type of organism, according to «Blackie’s Dictionary of Biology (opens in new tab)» (S Chand, 2014). For example, zoology is the study of animals, botany is the study of plants and microbiology is the study of microorganisms.

Within those broader fields, many biologists specialize in researching a specific topic or problem. For example, a scientist may study behavior of a certain fish species, while another scientist may research the neurological and chemical mechanisms behind the behavior.

There are numerous branches and subdisciplines of biology, but here is a short list of some of the more broad fields that fall under the umbrella of biology: 

Biochemistry: The study of the chemical processes that take place in or are related to living things, according to the Biochemical Society (opens in new tab). For example, pharmacology is a type of biochemistry research that focuses on studying how drugs interact with chemicals in the body, as described in a 2010 review in the journal Biochemistry. 

Ecology: The study of how organisms interact with their environment. For example, an ecologist may study how honeybee behavior is affected by humans living nearby. 

Genetics: The study of heredity. Geneticists study how genes are passed down by parents to their offspring, and how they vary from person to person. For example, scientists have identified several genes and genetic mutations that influence human lifespan, as reported in a 2019 review published in the journal Nature Reviews Genetics (opens in new tab).   

Physiology: The study of how living things work. Physiology, which is applicable to any living organism, «deals with the life-supporting functions and processes of living organisms or their parts,» according to Nature (opens in new tab). Physiologists seek to understand biological processes, such as how a particular organ works, what its function is and how it’s affected by outside stimuli. For example, physiologists have studied how listening to music can cause physical changes (opens in new tab) in the human body, such as a slower or faster heart rate, according to the journal Psychological Health Effects of Musical Experiences (opens in new tab). . 

The multidisciplinary nature of biology

Biology is often researched in conjunction with other fields of study, including mathematics, engineering and the social sciences. Here are a few examples:

Astrobiology is the study of the evolution of life in the universe, including the search for extraterrestrial life, according to NASA (opens in new tab). This field incorporates principles of biology with astronomy. 

Bioarchaeologists are biologists who incorporate archaeological techniques to study skeletal remains and derive insights about how people lived in the past, according to George Mason University (opens in new tab).

Bioengineering is the application of engineering principles to biology and vice versa, according to the University of California Berkeley (opens in new tab). For example, a bioengineer might develop a new medical technology that better images the inside of the body, like an improved Magnetic Resonance Imaging (MRI) that scans the human body at a faster rate and higher resolution, or apply biological knowledge to create artificial organs, according to the journal Cell Transplant.

Biotechnology involves using biological systems to develop products, according to the Norwegian University of Science and Technology (opens in new tab). For example, biotechnologists in Russia genetically engineered a better-tasting and more disease-resistant strawberry, which the researchers described in their 2007 study published in the journal Biotechnology and Sustainable Agriculture 2006 and Beyond (opens in new tab).  

Biophysics employs the principles of physics to understand how biological systems work, according to the Biophysical Society (opens in new tab). For example, biophysicists may study how genetic mutations leading to changes in protein structure impacts protein evolution, according to the Journal of the Royal Society

What do biologists do?

Biologists can work in many different fields, including research, healthcare, environmental conservation and art, according to the American Institute of Biological Sciences (opens in new tab). Here are a few examples:

Research: Biologists can perform research in many types of settings. Microbiologists, for instance, may study bacterial cultures in a laboratory setting. Other biologists may perform field research, where they observe animals or plants in their native habitat. Many biologists may work in the lab and in the field — for example, scientists may collect soil or water samples from the field and analyze them further in the  lab, like at North Carolina University’s Soil and Water Lab (opens in new tab).

Conservation: Biologists can help with efforts in environmental conservation by studying and determining how to protect and conserve the natural world for the future. For example, biologists may help educate the public on the importance of preserving an animal’s natural habitat and participate in endangered species recovery programs to stop the decline of an endangered species, according to the U.S. Fish & Wildlife Service (opens in new tab).

Healthcare: People who study biology can go on to work in healthcare, whether they work as doctors or nurses, join a pharmaceutical company to develop new drugs and vaccines, research the efficacy of medical treatments or become veterinarians to help treat sick animals, according to the American Institute of Biological Sciences (opens in new tab).

Art: Biologists who also have a background in art have both the technical knowledge and artistic skill to create visuals that will communicate complex biological information to a wide variety of audiences. One example of this is in medical illustration, in which an illustrator may perform background research, collaborate with experts, and observe a medical procedure to create an accurate visual of a body part, according to the Association of Medical Illustrators (opens in new tab).

Additional resources

If you’re curious about just how wide-reaching biology is, The University of North Carolina at Pembroke (opens in new tab) has listed a number of biology subdisciplines on their website. Interested in a career in biology? Check out some options at the American Institute of Biological Sciences (opens in new tab) website.

Bibliography

Lornande Loss Woodruff, “History of Biology”, The Scientific Monthly, Volume 12, March 1921, http://www.jstor.org/stable/6836 (opens in new tab).  

P.N. Campbell, “Biology in Profile: A Guide to the Many Branches of Biology (opens in new tab)”, Elsevier, October 2013. 

The University of North Carolina at Pembroke, “Biology Sub-disciplines (opens in new tab)”, October 2010. 

University of Minnesota Duluth, “What is Biology? (opens in new tab)”, January 2022. 

Eric J. Simon et al, “Campbell Essential Biology (opens in new tab)”, Pearson Education, January 2018. 

Alane Lim holds a Ph.D. in materials science and engineering from Northwestern University and a bachelor’s degrees in chemistry and cognitive science from Johns Hopkins University. She also has over five years of experience in writing about science for a variety of audiences. Her work has appeared on the science YouTube channel SciShow, the reference website ThoughtCo, and the American Institute of Physics.

Last Updated: April 20, 2022 | Author: howto-Trust

Contents

• 1 What does biology literally mean?
• 2 What does biology mean in simple words?
• 3 What does means stand for in biology?
• 4 What is biology example?
• 5 Who termed the word biology?
• 6 What does biological mean in medicine?
• 7 What is a biological daughter?
• 8 Is biology a science?
• 9 What is the difference between a drug and a biologic?
• 10 What is biological health?
• 11 Is biology a medical term?
• 12 Is Penicillin a biologic?
• 13 What do biologics do to the body?
• 14 Is apremilast a biologic?
• 15 Is aspirin a biologic?
• 16 Is insulin a biologic?
• 17 What disease did penicillin first cure?
• 18 Is Methotrexate a biologic?

What does biology literally mean?

The word biology is derived from the greek words /bios/ meaning /life/ and /logos/ meaning /study/ and is defined as the science of life and living organisms.

What does biology mean in simple words?

1 : a branch of science that deals with living organisms and vital processes. 2a : the plant and animal life of a region or environment. b : the laws and phenomena relating to an organism or group. 3 : a treatise on biology.

What does means stand for in biology?

mean. (Science: statistics) average value calculated by taking the sum of all values and dividing by the total number of values. Last updated on July 28th, 2021.

What is biology example?

The definition of biology is the science of all living organisms. An example of biology is one aspect of science a person would study in order to become a Forensic Scientist. … of living organisms, as plants and animals, and of viruses: it includes botany, zoology, and microbiology.

Who termed the word biology?

The term biology in its modern sense appears to have been introduced independently by Thomas Beddoes (in 1799), Karl Friedrich Burdach (in 1800), Gottfried Reinhold Treviranus (Biologie oder Philosophie der lebenden Natur, 1802) and Jean-Baptiste Lamarck (Hydrogéologie, 1802).

What does biological mean in medicine?

(bī’ō-loj’i-kal), A diagnosic, pregentive, or therapeutic preparation derived or obtained from living organisms and their product, for example, serum, vaccine, antigen, antitoxin.

What is a biological daughter?

biological daughter n

(female offspring by birth)

Is biology a science?

Biology is a branch of science that deals with living organisms and their vital processes. Biology encompasses diverse fields, including botany, conservation, ecology, evolution, genetics, marine biology, medicine, microbiology, molecular biology, physiology, and zoology.

What is the difference between a drug and a biologic?

A biologic is manufactured in a living system such as a microorganism, or plant or animal cells. … A drug is typically manufactured through chemical synthesis, which means that it is made by combining specific chemical ingredients in an ordered process.

What is biological health?

Biological health hazards include bacteria, viruses, parasites and moulds or fungi. … We provide expertise and resources on monitoring and controlling biological hazards that are transmitted through food, air or water.

Is biology a medical term?

Bio-: Prefix indicating living plants or creatures, as in biology (the study of living organisms).

Is Penicillin a biologic?

So how are biological drugs different from traditional drugs? Traditional drugs like aspirin, Lipitor, and penicillin are small molecule drugs with several dozen atoms made in bulk in a chemistry laboratory while biologics are usually large proteins with hundreds or thousands of atoms made inside living cells.

What do biologics do to the body?

Biologics. Biologics are a special type of powerful drug that slows or stops damaging inflammation. Biologics and biosimilars are special types of disease-modifying antirheumatic drugs (DMARD). In most cases, they are prescribed when conventional DMARDs have not worked.

Is apremilast a biologic?

Otezla (apremilast) is a small molecule phosphodiesterase 4 (PDE4) inhibitor but is not classified as a biologic. It is an oral tablet used to treat plaque psoriasis, psoriatic arthritis, and oral ulcers associated with Behçet’s Disease.

Is aspirin a biologic?

Common medicines such as aspirin, antacids and statins are chemical in nature. Though many were initially discovered in the wild (aspirin is a cousin of a compound in willow bark, the first statin was found in a fungus), these drugs are now made nonbiologically.

Is insulin a biologic?

Biologic medication: Biologic medications are large, complex molecules, often made from living cells or tissue. Insulin, Victoza^® and Trulicity^® are examples of biologic medications that help manage diabetes. Drugs: Drugs are smaller molecules that are made through a chemical process.

What disease did penicillin first cure?

Widespread use of Penicillin

The first patient was successfully treated for streptococcal septicemia in the United States in 1942.

Is Methotrexate a biologic?

Non-biologic RA drugs are better studied than the biologics. Non-biologics include: Methotrexate (Rheumatrex, Trexall, and generic) Leflunomide (Arava and generic)

Asked by: Vella Little III

Score: 4.9/5
(46 votes)

Biology is the scientific study of life. It is a natural science with a broad scope but has several unifying themes that tie it together as a single, coherent field. For instance, all organisms are made up of cells that process hereditary information encoded in genes, which can be transmitted to future generations.

What is the simple definition of biology?

The word biology is derived from the greek words /bios/ meaning /life/ and /logos/ meaning /study/ and is defined as the science of life and living organisms. An organism is a living entity consisting of one cell e.g. bacteria, or several cells e.g. animals, plants and fungi.

What is biology in short answer?

Biology is a branch of science that deals with living organisms and their vital processes. Biology encompasses diverse fields, including botany, conservation, ecology, evolution, genetics, marine biology, medicine, microbiology, molecular biology, physiology, and zoology.

What is biology example?

The definition of biology is the science of all living organisms. An example of biology is one aspect of science a person would study in order to become a Forensic Scientist. … of living organisms, as plants and animals, and of viruses: it includes botany, zoology, and microbiology.

What are types of biology?

There are three main recognized branches of biology, which include botany, zoology, and microbiology.

30 related questions found

biology, study of living things and their vital processes. The field deals with all the physicochemical aspects of life. The modern tendency toward cross-disciplinary research and the unification of scientific knowledge and investigation from different fields has resulted in significant overlap of the field of biology with other scientific disciplines. Modern principles of other fields—chemistry, medicine, and physics, for example—are integrated with those of biology in areas such as biochemistry, biomedicine, and biophysics.

Biology is subdivided into separate branches for convenience of study, though all the subdivisions are interrelated by basic principles. Thus, while it is custom to separate the study of plants (botany) from that of animals (zoology), and the study of the structure of organisms (morphology) from that of function (physiology), all living things share in common certain biological phenomena—for example, various means of reproduction, cell division, and the transmission of genetic material.

Biology is often approached on the basis of levels that deal with fundamental units of life. At the level of molecular biology, for example, life is regarded as a manifestation of chemical and energy transformations that occur among the many chemical constituents that compose an organism. As a result of the development of increasingly powerful and precise laboratory instruments and techniques, it is possible to understand and define with high precision and accuracy not only the ultimate physiochemical organization (ultrastructure) of the molecules in living matter but also the way living matter reproduces at the molecular level. Especially crucial to those advances was the rise of genomics in the late 20th and early 21st centuries.

Cell biology is the study of cells—the fundamental units of structure and function in living organisms. Cells were first observed in the 17th century, when the compound microscope was invented. Before that time, the individual organism was studied as a whole in a field known as organismic biology; that area of research remains an important component of the biological sciences. Population biology deals with groups or populations of organisms that inhabit a given area or region. Included at that level are studies of the roles that specific kinds of plants and animals play in the complex and self-perpetuating interrelationships that exist between the living and the nonliving world, as well as studies of the built-in controls that maintain those relationships naturally. Those broadly based levels—molecules, cells, whole organisms, and populations—may be further subdivided for study, giving rise to specializations such as morphology, taxonomy, biophysics, biochemistry, genetics, epigenetics, and ecology. A field of biology may be especially concerned with the investigation of one kind of living thing—for example, the study of birds in ornithology, the study of fishes in ichthyology, or the study of microorganisms in microbiology.

Britannica Quiz

Chemistry and Biology: Fact or Fiction?

Basic concepts of biology

Biological principles

Homeostasis

The concept of homeostasis—that living things maintain a constant internal environment—was first suggested in the 19th century by French physiologist Claude Bernard, who stated that “all the vital mechanisms, varied as they are, have only one object: that of preserving constant the conditions of life.”

As originally conceived by Bernard, homeostasis applied to the struggle of a single organism to survive. The concept was later extended to include any biological system from the cell to the entire biosphere, all the areas of Earth inhabited by living things.

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Unity

All living organisms, regardless of their uniqueness, have certain biological, chemical, and physical characteristics in common. All, for example, are composed of basic units known as cells and of the same chemical substances, which, when analyzed, exhibit noteworthy similarities, even in such disparate organisms as bacteria and humans. Furthermore, since the action of any organism is determined by the manner in which its cells interact and since all cells interact in much the same way, the basic functioning of all organisms is also similar.

There is not only unity of basic living substance and functioning but also unity of origin of all living things. According to a theory proposed in 1855 by German pathologist Rudolf Virchow, “all living cells arise from pre-existing living cells.” That theory appears to be true for all living things at the present time under existing environmental conditions. If, however, life originated on Earth more than once in the past, the fact that all organisms have a sameness of basic structure, composition, and function would seem to indicate that only one original type succeeded.

A common origin of life would explain why in humans or bacteria—and in all forms of life in between—the same chemical substance, deoxyribonucleic acid (DNA), in the form of genes accounts for the ability of all living matter to replicate itself exactly and to transmit genetic information from parent to offspring. Furthermore, the mechanisms for that transmittal follow a pattern that is the same in all organisms.

Whenever a change in a gene (a mutation) occurs, there is a change of some kind in the organism that contains the gene. It is this universal phenomenon that gives rise to the differences (variations) in populations of organisms from which nature selects for survival those that are best able to cope with changing conditions in the environment.

Biology is the branch of science that primarily deals with the structure, function, growth, evolution, and distribution of organisms. As a science, it is a methodological study of life and living things. It determines verifiable facts or formulates theories based on experimental findings on living things by applying the scientific method. An expert in this field is called a biologist.

Some of the common objectives of their research include understanding the life processes, determining biological processes and mechanisms, and how these findings can be used in medicine and industry. Thus, biological research settings vary, e.g. inside a laboratory or in the wild.

Biology is a wide-ranging field. It encompasses various fields in science, such as chemistry, physics, mathematics, and medicine. Biochemistry, for instance, is biology and chemistry combined. It deals primarily with the diverse biomolecules (e.g. nucleic acids, proteins, carbohydrates, and lipids), studying biomolecular structures and functions. Biophysics is another interdisciplinary field that applies approaches in physics to understand biological phenomena.

Mathematics and biology have also gone hand in hand to come up with theoretical models to elucidate biological processes using mathematical techniques and tools. Medical biology or biomedicine is another major integration where medicine makes use of biological principles in clinical settings. These are just a few of the many biology examples wherein its fundamental tenets are integrated into other scientific fields.

Etymology

Introduction to Biology

A basic biology definition would be is that it is the study of living organisms. It is concerned with all that has life and living. (Ref.1) In contrast to inanimate objects, a living matter is one that demonstrates life. For instance, a living thing would be one that is comprised of a cell or a group of cells.

Each of these cells can carry out processes, e.g. anabolic and catabolic reactions, in order to sustain life. These reactions may be energy-requiring. They are also regulated through homeostatic mechanisms. A living matter would also be one that is capable of reacting to stimuli, adapt to its environment, reproduce, and grow.

The major groups of living things are animals, plants, fungi, protists, bacteria, and archaea. Biology studies their structure, function, distribution, evolution, and taxonomy.

Recommended: BLASTing through the kingdom of life – a guide for teachers, from Digitalworldbiology.com.

Modern Principles and Concepts of Biology

The fundamental principles of biology that are acceptable to this day include cell theory, gene theory, evolutionary theory, homeostasis, and energy.

Cell theory

Cell theory is a scientific theory proposed by the scientists, Theodor Schwann, Matthias Jakob Schleiden, and Rudolf Virchow. It is formulated to refute the old theory, Spontaneous generation. It suggests the following tenets: (1) All living things are made up of one or more cells, (2) the cell is the structural and functional unit, (3) cells come from a pre-existing process of division, (4) all cells have the same chemical composition, and (5) energy flow occurs within the cell. (Ref.2)

Gene theory

In Gene theory, the gene is considered as the fundamental, physical, and functional unit of heredity. (Ref.3) It is located on the chromosome and contains DNA. The gene stores the genetic code, i.e. a sequence of nucleotides that determines the structure of a protein or RNA. A gene is a unit of heredity because it is transmitted across generations. It is through which the phenotypic trait of an organism is based upon.

Gregor Johann Mendel was one of the main pioneers that established the science of genetics. As such, he is regarded as the father of the said field. He was able to determine the occurrence of unit factors (now referred to as genes) that were passed down from one generation to the next. He described these unit factors as occurring in pairs. One of the pairs will be dominant over the other (recessive). He formulated the Mendelian laws to elucidate how heredity occurs.

These laws include Law of Segregation, Law of Independent Assortment, and Law of Dominance. The inheritance pattern that follows these laws is referred to as Mendelian inheritance. Conversely, an inheritance pattern that does not conform to these laws is described as Non-Mendelian.

Evolutionary theory

Evolution pertains to the genetic changes in a population over successive generations driven by natural selection, mutation, hybridization, or inbreeding. (Ref.4) Charles Darwin is one of the major contributors to the theory of evolution. He is known for his work Origin of Species by Natural Selection after his Beagle voyage.

He was able to observe different plant and animal species. Based on his analysis, he postulated that living things have an inherent tendency to produce offspring of the same kind. Thus, the survival of the species becomes dependent on the available food and space. As a result, organisms compete as the carrying capacity of the habitat would not be able to sustain a massive population. (Ref.5) Survival or struggle for existence, thus, becomes an individual feat.

Homeostasis

Homeostasis is the tendency of an organism to maintain optimal internal conditions. It entails a system of feedback controls so as to stabilize and keep up with the normal homeostatic range despite the changing external conditions. For instance, it employs homeostatic mechanisms to regulate temperature, pH, and blood pressure.

The homeostatic system is comprised of three main components: a receptor, a control center, and an effector. The receptor of the homeostatic system includes the various sensory receptors that can detect external and internal changes. The information is sent to the control center to process it and to produce a signal to incite an appropriate response from the effector. The concept of homeostasis is credited to Claude Bernard in 1865.

Energy

In biology, energy is essential to drive various biological processes, especially anabolic reactions. Adenosine triphosphate (ATP) is the main energy carrier of the cell. It is released from carbohydrates through glycolysis, fermentation, and oxidative phosphorylation. Lipids are another group of biomolecules that store energy.

Importance of Biology

Biology is the scientific way to understand life. Knowing the biological processes and functions of life is essential to gain a deeper knowledge and appreciation in life. Furthermore, it opens an avenue of resources for use in medicine and industry. How a biological process proceeds, its regulatory systems, and its components can lead to better awareness. For example, conservation efforts could begin to save a species that has been classified as endangered, i.e. on the verge of extinction.

Research

A specialist or an expert in the field of biology is called a biologist. Biologists look upon the biophysical, biomolecular, cellular, and systemic levels of an organism. They attempt to understand the mechanisms at play in various biological processes that govern life. They are also interested in coming up with innovations to create and improve life. Some of them have advocacies and are concerned with the conservation of species. Depending on the nature and objectives of their research, they may be found conducting research inside a laboratory. Others carry out their scientific pursuits outside, such as in diverse habitats where an organism or a population of organisms thrive.

The biological study can be traced back to early times. Aristotle, for instance, was a Greek philosopher in Athens known for his contributions to philosophy and biology. He was the first person to study biology systematically. Some of his popular works include the History of Animals, Generation of Animals, Movement of Animals, Parts of Animals. Much of his botanical studies, though, were lost. Because of his many pioneering studies, he is regarded by many as the “Father of Biology”.

At present, biologists are now seeking the potential use of biology in other fields, such as medicine, agriculture, and industry. One of the most recent breakthroughs is CRISPR — a gene-hacking tool used by scientists to splice specific DNA targets and then replace them with a DNA that would yield the desired effect. One of its promises is that it can correct physiological anomalies due to mutated or defective gene mutations. (Ref.6)

Authors can now submit preprints to bioRxiv — an online archive and distribution service for preprints in the life sciences. More details here: BioTechniques Welcomes Preprints – BioTechniques (BioTechniques: https://www.biotechniques.com/general-interest/biotechniques-welcomes-preprints/).

Branches of Biology

Biology encompasses various sub-disciplines or branches. Some of the branches of biology are as follows:

• Anatomy – the study of the animal form, particularly the human body
• Astrobiology – the branch of biology concerned with the effects of outer space on living organisms and the search for extraterrestrial life
• Biochemistry – the study of the structure and function of cellular components, such as proteins, carbohydrates, lipids, nucleic acids, and other biomolecules, and of their functions and transformations during life processes
• Bioclimatology – a science concerned with the influence of climates on organisms, for instance, the effects of climate on the development and distribution of plants, animals, and humans
• Bioengineering – or biological engineering, a broad-based engineering discipline that deals with bio-molecular and molecular processes, product design, sustainability, and analysis of biological systems
• Biogeography – a science that attempts to describe the changing distributions and geographic patterns of living and fossil species of plants and animals
• Bioinformatics – information technology as applied to the life sciences, especially the technology used for the collection, storage, and retrieval of genomic data
• Biomathematics – mathematical biology or biomathematics, an interdisciplinary field of academic study which aims at modeling natural, biological processes using mathematical techniques and tools. It has both practical and theoretical applications in biological research
• Biophysics – or biological physics, interdisciplinary science that applies the theories and methods of physical sciences to questions of biology
• Biotechnology – applied science concerned with biological systems, living organisms, or derivatives thereof, to make or modify products or processes for specific use
• Botany – the scientific study of plants
• Cell biology – the study of cells at the microscopic or at the molecular level. It includes studying the cells’ physiological properties, structures, organelles, interactions with their environment, life cycle, cell division, and apoptosis
• Chronobiology – a science that studies time-related phenomena in living organisms
• Conservation Biology – concerned with the studies and schemes of habitat preservation and species protection for the purpose of alleviating extinction crisis and conserving biodiversity
• Cryobiology – the study of the effects of low temperatures on living organisms
• Developmental Biology – the study of the processes by which an organism develops from a zygote to its full structure
• Ecology – the scientific study of the relationships between plants, animals, and their environment
• Ethnobiology – a study of the past and present human interactions with the environment, for instance, the use of diverse flora and fauna by indigenous societies
• Evolutionary Biology – a subfield concerned with the origin and descent of species, as well as their change over time, i.e. their evolution
• Freshwater Biology – a science concerned with the life and ecosystems of freshwater habitats
• Genetics – a science that deals with heredity, especially the mechanisms of hereditary transmission and the variation of inherited characteristics among similar or related organisms
• Geobiology – a science that combines geology and biology to study the interactions of organisms with their environment
• Immunobiology – a study of the structure and function of the immune system, innate and acquired immunity, the bodily distinction of self from non-self, and laboratory techniques involving the interaction of antigens with specific antibodies
• Marine Biology – the study of ocean plants and animals and their ecological relationships
• Medicine – the science which relates to the prevention, cure, or alleviation of disease
• Microbiology – the branch of biology that deals with microorganisms and their effects on other living organisms
• Molecular Biology – the branch of biology that deals with the formation, structure, and function of macromolecules essential to life, such as nucleic acids and proteins, and especially with their role in cell replication and the transmission of genetic information
• Mycology – the study of fungi
• Neurobiology – the branch of biology that deals with the anatomy, physiology, and pathology of the nervous system
• Paleobiology – the study of the forms of life existing in prehistoric or geologic times, as represented by the fossils of plants, animals, and other organisms
• Parasitology – the study of parasites and parasitism
• Pathology – the study of the nature of the disease and its causes, processes, development, and consequences
• Pharmacology – the study of preparation and use of drugs and synthetic medicines
• Physiology – the biological study of the functions of living organisms and their parts
• Protistology – the study of protists
• Psychobiology – the study of mental functioning and behavior in relation to other biological processes
• Toxicology – the study of how natural or man-made poisons cause undesirable effects in living organisms
• Virology – the study of viruses
• Zoology – The branch of biology that deals with animals and animal life, including the study of the structure, physiology, development, and classification of animals
• Ethology – the study of animal behavior
• Entomology – the scientific study of insects
• Ichthyology – the study of fishes
• Herpetology – the science of reptiles and amphibians
• Ornithology – the science of birds
• Mammalogy – the study of mammals
• Primatology – the science that deals with primates

Human Biology – Definition

Human biology is the branch of biology that focuses on humans in terms of evolution, genetics, anatomy and physiology, ecology, epidemiology, and anthropology. It can be a subfield of Primatology since humans belong to the group of primates, particularly of the family Hominidae (tribe Hominini). Since human biology is a course that deals mainly with humans, it is a viable option for use as a preparatory course in medicine.

Try to answer the quiz below to check what you have learned so far about biology.

See Also

• Organism

References

1. INTRODUCTION: THE NATURE OF SCIENCE AND BIOLOGY. (2019). Retrieved September 12, 2019, from Estrellamountain.edu website: http://www2.estrellamountain.edu/faculty/farabee/biobk/biobookintro.html
2. 4.1C: Cell Theory. (2019, September 9). Retrieved from Biology LibreTexts website: https://bio.libretexts.org/Bookshelves/Introductory-and-General-Biology/Book:-General-Biology-(Boundless)/4:-Cell-Structure/4.1:-Studying-Cells/4.1C:-Cell-Theory
3. Rheinberger, H.-J., Müller-Wille, S., & Meunier, R. (2015). Gene (Stanford Encyclopedia of Philosophy). Retrieved September 12, 2019, from Stanford.edu website: https://plato.stanford.edu/entries/gene/
4. A brief history of evolution. (2019). Retrieved from OpenLearn website: https://www.open.edu/openlearn/history-the-arts/history/history-science-technology-and-medicine/history-science/brief-history-evolution
5. 3. Theories of Evolution. (2010). Retrieved from BIOLOGY4ISC website: https://biology4isc.weebly.com/3-theories-of-evolution.html
6. Gonzaga, M. V. (2019, August 21). CRISPR DIY – biohacking genes at. Retrieved from Biology Blog & Dictionary Online website: https://www.biologyonline.com/crispr-diy-biohacking-genes-at-home/

Recommended Source

• The Society for Experimental Biology (SEB) – get the latest news on cell biology, plant biology, animal biology, and more.

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Biology is the «science of life.» It is the study of living and once-living things, from submicroscopic structures in single-celled organisms to entire ecosystems with billions of interacting organisms; it further ranges in time focus from a single metabolic reaction inside a cell to the life history of one individual and on to the course of many species over eons of time. Biologists study the characteristics and behaviors of organisms, how species and individuals come into existence, and their interactions with each other and with the environment. The purview of biology extends from the origin of life to the fundamental nature of human beings and their relationship to all other forms of life.

Biology, or «life science,» offers a window into fundamental principles shared by living organisms. These principles reveal a harmony and unity of the living world operating simultaneously among a great diversity of species and even in the midst of competition both between and within species for scarce resources. The overlying harmony is seen at each level, from within a cell to the level of systems in individuals (nervous, circulatory, respiratory, etc.), the immediate interactions of one organism with others, and on to the complex of organisms and interactions comprising an ecosystem with a multitude of ecological niches each supporting one species. Such harmony is manifested in many universally shared characteristics among living beings, including interdependence, a common carbon-based biochemistry, a widespread pattern of complementary polarities, sexual reproduction, and homeostasis.

As the science dealing with all life, biology encompasses a broad spectrum of academic fields that have often been viewed as independent disciplines. Among these are molecular biology, biochemistry, cell biology, physiology, anatomy, developmental biology, genetics, ecology, paleontology, and evolutionary biology. While competition among individuals expressing genetic variability has generally been identified as a key factor in evolutionary development, the pivotal roles of cooperation^[1] and long-term symbiosis or symbiogenesis (Margulis and Sagan 2002) in living systems have emerged in the late twentieth century as essential complementary focal points for understanding both the origin of species and the dynamics of biological systems.

Principles of biology

While biology is unlike physics in that it does not usually describe biological systems in terms of objects that exclusively obey immutable physical laws described by mathematics, it is nevertheless characterized by several major principles and concepts, which include: universality, evolution, interactions, diversity, and continuity.

Universality: Cells, biochemistry, energy, development, homeostasis, and polarity

See also: Life

Living organisms share many universal characteristics, including that they are composed of cells; pass on their heredity using a nearly universal genetic code; need energy from the environment to exist, grow, and reproduce; maintain their internal environment; and exhibit dual characteristics or complementary polarities. This are the common set of characteristics identified by biologists that distinguish living organisms from nonliving things.

With the exception of viruses, all organisms consist of cells, which are the basic units of life, being the smallest unit that can carry on all the processes of life, including maintenance, growth, and even self-repair. Some simple life forms, such as the paramecium, consist of a single cell throughout their life cycle and are called unicellular organisms. Multicellular organisms, such as a whale or tree, may have trillions of cells differentiated into many diverse types each performing a specific function.

All cells, in turn, are based on a carbon-based biochemistry, and all organisms pass on their heredity via genetic material based on nucleic acids such as DNA using a nearly universal genetic code. Every cell, no matter how simple or complex, utilizes nucleic acids for transmitting and storing the information needed for manufacturing proteins.

Every living being needs energy from the environment in order to exist, grow, and reproduce. Radiation from the sun is the main source of energy for life and is captured through photosynthesis, the biochemical process in which plants, algae, and some bacteria harness the energy of sunlight to produce food. Ultimately, nearly all living things depend on energy produced from photosynthesis for their nourishment, making it vital to life on Earth. There are also some bacteria that utilize the oxidation of inorganic compounds such as hydrogen sulfide or ferrous iron as an energy source. An organism that produces organic compounds from carbon dioxide as a carbon source, using either light or reactions of inorganic chemical compounds as a source of energy, is called an autotroph. Other organisms do not make their own food but depend directly or indirectly on autotrophs for their food. These are called heterotrophs.

In development, the theme of universal processes is also present. Living things grow and develop as they age. In most metazoan organisms the basic steps of the early embryo development share similar morphological stages and include similar genes.

All living organisms, whether unicellular or multicellular, exhibit homeostasis. Homeostasis is the property of an open system to regulate its internal environment so as to maintain a stable condition. Homeostasis can manifest itself at the cellular level through the maintenance of a stable internal acidity (pH); at the organismal level, warm-blooded animals maintain a constant internal body temperature; and at the level of the ecosystem, for example when atmospheric carbon dioxide levels rise, plants are theoretically able to grow healthier and thus remove more carbon dioxide from the atmosphere. Tissues and organs can also maintain homeostasis.

In addition, living beings share with all existent beings the quality of dual characteristics or complementary polarities. One common pair of dual characteristics is the quality of positivity and negativity: Just as sub-atomic particles have positive (electron) and negative (proton) elements that interrelate and form atoms, living beings commonly exhibit positive and negative characteristics. Most animals reproduce through relationships between male and female, and higher plants likewise have male and female elements, such as the (male) stamen and (female) pistil in flowering plants (angiosperms). Lower plants, fungi, some of the protists, and bacteria likewise exhibit reproductive variances, which are usually symbolized by + and — signs (rather than being called male and female), and referred to as «mating strains» or «reproductive types» or similar appellations.

Another more philosophical concept is the universal dual characteristic of within each organism of the invisible, internal character or nature and the visible aspects of matter, structure, and shape. For example, an animal will exhibit the internal aspects of life, instinct, and function of its cells, tissues, and organs, which relate with the visible shape made up by those cells, tissues, and organs.

Sexual reproduction is a trait that is almost universal among eukaryotes. Asexual reproduction is not uncommon among living organisms. In fact, it is widespread among fungi and bacteria, many insects reproduce in this manner, and some reptiles and amphibians. Nonetheless, with the exception of bacteria (prokaryotes), sexual reproduction is also seen in these same groups. (Some treat the unidirectional lateral transfer of genetic material in bacteria, between donors (+ mating type) and recipients (- mating type), as a type of sexual reproduction.) Evolutionary biologist and geneticist John Maynard Smith maintained that the perceived advantage for an individual organism to pass only its own entire genome to its offspring is so great that there must be an advantage by at least a factor of two to explain why nearly all animal species maintain a male sex.

Another characteristic of living things is that they take substances from the environment and organize them in complex hierarchical levels. For example, in multicellular organisms, cells are organized into tissues, tissues are organized into organs, and organs are organized into systems.

In addition, all living beings respond to the environment; that is, they react to a stimulus. A cockroach may respond to light by running for a dark place. When there is a complex set of response, it is called a behavior. For example, the migration of salmon is a behavioral response.

Evolution: A common organizing principle of biology

See also: Evolution

A central, organizing concept in biology is that all life has descended from a common origin through a process of evolution. Indeed, eminent evolutionist Theodosius Dobzhansky has stated that «Nothing in biology makes sense except in the light of evolution.» Evolution can be considered a unifying theme of biology because the concept of descent with modification helps to explain the common carbon-based biochemistry, the nearly universal genetic code, and the similarities and relationships among living organisms, as well as between organisms of the past with organisms today.

Evolutionary theory actually comprises several distinct components. Two of the major strands are the theory of descent with modification, which addresses the «pattern» of evolution, and the theory of natural selection, which addresses the «process» of evolution. Charles Darwin established evolution as a viable theory by marshaling and systematizing considerable evidence for the theory of descent with modification, including evidence from paleontology, classification, biogeography, morphology, and embryology. The mechanism that Darwin postulated, natural selection, aims to account for evolutionary changes at both the microevolutionary level (i.e., gene changes on the populational level) and the macroevolutionary level (i.e., major transitions between species and origination of new designs). Experimental tests and observations provide strong evidence for microevolutionary change directed by natural selection operating on heritable expressed variation, while evidence that natural selection directs macroevolution is limited to fossil evidence of some key transition sequences and extrapolation from evidences on the microevolutionary level. (Alfred Russel Wallace is commonly recognized as proposing the theory of natural selection at about the same time as Darwin.)

The evolutionary history of a species—which tells the characteristics of the various species from which it descended—together with its genealogical relationship to every other species is called its phylogeny. Widely varied approaches to biology generate information about phylogeny. These include the comparisons of DNA sequences conducted within molecular biology or genomics, and comparisons of fossils or other records of ancient organisms in paleontology. Biologists organize and analyze evolutionary relationships
through various methods, including phylogenetics, phenetics, and cladistics. Major events in the evolution of life, as biologists currently understand them, are summarized on an evolutionary timeline.

Interactions: Harmony and bi-level functionality

Every living thing interacts with other organisms and its environment. One of the reasons that biological systems can be difficult to study is that there are so many different possible interactions with other organisms and the environment. A microscopic bacterium responding to a local gradient in sugar is as much responding to its environment as a lion is responding to its environment when it is searching for food in the African savanna. Within a particular species, behaviors can be cooperative, aggressive, parasitic, or symbiotic.

Matters become more complex still when two or more different species interact in an ecosystem, studies of which lie in the province of ecology. Analysis of ecosystems shows that a major factor in maintaining harmony and reducing competition is the tendency for each species to find and occupy a distinctive niche not occupied by other species.

Overlying the interactions of organisms is a sense of unity and harmony at each level of interaction. On the global level, for example, one can see the harmony between plant and animal life in terms of photosynthesis and respiration. Plants, through photosynthesis, use carbon dioxide and give off oxygen. While they also respire, plants’ net input to the globe is considerably more oxygen than they consume (with algae in the ocean being a major source of planetary oxygen). Animals, on the other hand, consume oxygen and discharge carbon dioxide.

On the trophic level, the food web demonstrates harmony. Plants convert and store the sun’s energy. These plants serve as food for herbivores, which in turn serve as food for carnivores, which are consumed by top carnivores. Top carnivores (and species at all other trophic levels), when dead, are broken down by decomposers such as bacteria, fungi, and some insects into minerals and humus in the soil, which is then used by plants.

On the level of individuals, the remarkable harmony among systems (nervous, circulatory, respiratory, endocrine, reproductive, skeletal, digestive, etc.) is a wonder to behold. Even within a cell, one sees remarkable examples of unity and harmony, such as when a cell provides a product to the body (such as a hormone) and receives oxygen and nourishment from the body. So remarkable is the harmony evident among organisms, and between organisms and the environment, that some have proposed a theory that the entire globe acts as if one, giant, functioning organism (the Gaia theory). According to well-known biologist Lynn Margulis and science writer Dorion Sagan (Microcosmos, 1997), even evolution is tied to cooperation and mutual dependence among organisms: «Life did not take over the globe by combat, but by networking.»

An underlying explanation for such observed harmony is the concept of bi-level functionality, the view that every entity exists in an integral relation with other entities in ways that permit an individual entity to advance its own multiplication, development, self-preservation, and self-strengthening (a function for the individual) while at the same time contribute toward maintaining or developing the larger whole (a function for the whole). These functions are not independent but interdependent. The individual’s own success allows it to contribute to the whole, and while the individual contributes something of value to the larger entity, assisting the larger entity in advancing its own function, the larger entity likewise provides the environment for the success of the individual.

For example, in the cells of a multicellular organism, each cell provides a useful function for the body as a whole. A cell’s function may be to convert sugar to ADP energy, attack foreign invaders, or produce hormones. A cell in the epithelial tissue of the stomach may secrete the enzyme pepsin to help with digestion. The cell’s function of providing pepsin to the body is harmonized with the body’s needs for maintenance, development, and reproduction. The body, on the other hand, supports the individual cell and its function by providing food, oxygen, and other necessary materials, and by transporting away the toxic waste materials. Each cell actually depends on the other cells in the body to perform their functions and thus keep the body in proper functioning order. Likewise, a particular taxonomic group (taxa) not only advances its own survival and reproduction, but also provides a function for the ecosystems of which it is part, such as the ocelot species helping to regulate prey populations and thus help ecosystems to maintain balance. An ecosystem provides an environment for the success of this taxonomic group and thus its contribution to the ecosystem. In essence, this explanation holds that while animals and plants may seem to struggle against one another for existence, in reality they do not. Rather, they all contribute to the whole, in harmony.

Human beings, the most complex of all biological organisms, likewise live in a biosphere that is all interrelated and is necessary for physical life. Thus, it becomes essential that human beings, as the most powerful of all life forms and in many ways an encapsulation of the whole (a «microcosm of creation» according to a theological perspective^[2]), understand and care for the environment. In religious terms, this is sometimes referred to as the «third blessing,» the role of humankind to love and care for creation. The science of biology is central to this process.

The science of physics offers complementary rationales both for explaining evolutionary development and also for urging humans to love and care for the biosphere. This striking advance in physics arises through the extension of the second law of thermodynamics to apply to «open» systems, which include all forms of life. The extended second law states simply that natural processes in open systems tend to dissipate order as rapidly as possible. From this perspective, evolution of life’s successively more ordered and complex systems occurs because the greater a system’s order and complexity, the greater its capacity to dissipate order. Human beings, as the planet’s dominant and most complex species, face a thermodynamic imperative to apply themselves toward establishing an even greater level of order and dynamic complexity on the planet. Achieving such greater order would likely require that humans learn to live together in peace while living in synergy with the biosphere.

Diversity: The variety of living organisms

See also: Diversity of Life

Despite the underlying unity, life exhibits an astonishing wide diversity in morphology, behavior, and life histories. In order to grapple with this diversity, biologists, following a conventional western scientific approach and historically unaware of the profound interdependence of all life on the planet, attempt to classify all living things. This scientific classification should reflect the evolutionary trees (phylogenetic trees) of the different organisms. Such classifications are the province of the disciplines of systematics and taxonomy. Taxonomy puts organisms in groups called taxa, while systematics seeks their relationships.

Until the nineteenth century, living organisms were generally divided into two kingdoms: animal and plant, or the Animalia and the Plantae. As evidence accumulated that these divisions were insufficient to express the diversity of life, schemes with three, four, or more kingdoms were proposed.

A popular scheme, developed in 1969 by Robert Whitaker, delineates living organisms into five kingdoms:

Monera — Protista — Fungi — Plantae —Animalia.

In the six-kingdom classification, the six top-level groupings (kingdoms) are:

Archaebacteria, Monera (the bacteria and cyanobacteria), Protista, Fungi, Plantae, and Animalia.

These schemes coexist with another scheme that divides living organisms into the two main divisions of prokaryote (cells that lack a nucleus: bacteria, etc.) and eukaryote (cells that have a nucleus and membrane-bound organelles: animals, plants, fungi, and protists).

In 1990, another scheme, a three-domain system, was introduced by Carl Woese and has became very popular (with the «domain» a classification level higher than kingdom):

Archaea (originally Archaebacteria) — Bacteria (originally Eubacteria) — Eukaryota (or Eucarya).

The three-domain system is a biological classification that emphasizes his separation of prokaryotes into two groups, the Bacteria and the Archaea (originally called Eubacteria and Archaebacteria). When recent work revealed that what were once called «prokaryotes» are far more diverse than suspected, the prokaryotes were divided into the two domains of the Bacteria and the Archaea, which are considered to be as different from each other as either is from the eukaryotes. Woese argued based on differences in 16S ribosomal RNA genes that these two groups and the eukaryotes each arose separately from an ancestral progenote with poorly developed genetic machinery. To reflect these primary lines of descent, he treated each as a domain, divided into several different kingdoms. The groups were also renamed the Bacteria, Archaea, and Eukaryota, further emphasizing the separate identity of the two prokaryote groups.

There is also a series of intracellular «parasites» that are progressively less alive in terms of being metabolically active:

Viruses — Viroids — Prions

Continuity: The common descent of life

See also: Descent with Modification

A group of organisms is said to have common descent if they have a common ancestor. All existing organisms on Earth are descended from a common ancestor or ancestral gene pool. This «last universal common ancestor,» that is, the most recent common ancestor of all organisms, is believed to have appeared about 3.5 billion years ago. (See: Origin of life.)

The notion that «all life [is] from [an] egg» (from the Latin «Omne vivum ex ovo») is a foundational concept of modern biology, it means that there has been an unbroken continuity of life from the initial origin of life to the present time. Up into the nineteenth century it was commonly believed that life forms can appear spontaneously under certain conditions ( abiogenesis).

The universality of the genetic code is generally regarded by biologists as strong support of the theory of universal common descent (UCD) for all bacteria, archaea, and eukaryotes.

Scope of biology

Academic disciplines

Biologists study life over a wide range of scales: Life is studied at the atomic and molecular scale in molecular biology, biochemistry, and molecular genetics. At the level of the cell, life is studied in cell biology, and at multicellular scales, it is examined in physiology, anatomy, and histology. Developmental biology involves study of life at the level of the development or ontogeny of an individual organism.

Moving up the scale toward more than one organism, genetics considers how heredity works between parent and offspring. Ethology considers group behavior of organisms. Population genetics looks at the level of an entire population, and systematics considers the multi-species scale of lineages. Interdependent populations and their habitats are examined in ecology.

Two broad disciplines within biology are botany, the study of plants, and zoology, the study of animals. Paleontology is inquiry into the developing history of life on earth, based on working with fossils, and includes the main subfields of paleobotany, paleozoology, and micropaleontology. Changes over time, whether within populations (microevolution) or involving either speciation or the introduction of major designs (macroevolution), is part of the field of inquiry of evolutionary biology. A speculative new field is astrobiology (or xenobiology) which examines the possibility of life beyond the Earth.

Biology has become such a vast research enterprise that it is not generally studied as a single discipline, but as a number of clustered sub-disciplines. Four broad groupings are considered here. The first broad group consists of disciplines that study the basic structures of living systems: cells, genes, and so forth; a second grouping considers the operation of these structures at the level of tissues, organs and bodies; a third grouping considers organisms and their histories; and a final constellation of disciplines focuses on the interactions. It is important to note, however, that these groupings are a simplified description of biological research. In reality, the boundaries between disciplines are very fluid and most disciplines borrow techniques from each other frequently. For example, evolutionary biology leans heavily on techniques from molecular biology to determine DNA sequences that assist in understanding the genetic variation of a population; and physiology borrows extensively from cell biology in describing the function of organ systems.

Ethical aspects

As in all sciences, biological disciplines are best pursued by persons committed to high ethical standards, maintaining the highest integrity and following a good research methodology. Data should be interpreted honestly, and results that do not fit one’s preconceived biases should not be discarded or ignored in favor of data that fits one’s prejudices. A biologist who puts her or his own well-being first (money, popularity, position, etc.), runs the risk of faulty or even fraudulent research. But even well-meaning biologists have gone off course in trying to fit research findings to personal biases.

Also overlying work in many biological fields is the more specific concept of bioethics. This is the discipline dealing with the ethical implications of biological research and its applications. Aspects of biology raising issues of bioethics include cloning, genetic engineering, population control, medical research on animals, creation of biological weapons, and so forth.

Structure of life

See also: Molecular biology, Cell biology, Genetics, and Developmental biology

Molecular biology is the study of biology at the molecular level. The field overlaps with other areas of biology, particularly genetics and biochemistry. Molecular biology chiefly concerns itself with understanding the interactions between the various systems of a cell, especially by mapping the interactions between DNA, RNA, and protein synthesis and learning how these interactions are regulated.

Cell biology studies the physiological properties of cells, as well as their behaviors, interactions, and environment; this is done both on a microscopic and molecular level. Cell biology researches both single-celled organisms like bacteria and specialized cells in multicellular organisms like humans.

Understanding the composition of cells and how cells work is fundamental to all of the biological sciences. Appreciating the similarities and differences between cell types is particularly important to the fields of cell and molecular biology. These fundamental similarities and differences provide a unifying theme, allowing the principles learned from studying one cell type to be extrapolated and generalized to other cell types.

Genetics is the science of genes, heredity, and the variation of organisms.
In modern research, genetics provides important tools in the investigation of the function of a particular gene (e.g., analysis of genetic interactions). Within organisms, genetic information generally is carried in chromosomes, where it is represented in the chemical structure of particular DNA molecules.

Genes encode the information necessary for synthesizing proteins, which in turn play a large role in influencing the final phenotype of the organism, although in many instances do not completely determine it.

Developmental biology studies the process by which organisms grow and develop. Originating in embryology, today, developmental biology studies the genetic control of cell growth, differentiation, and «morphogenesis,» which is the process that gives rise to tissues, organs, and anatomy.
Model organisms for developmental biology include the round worm Caenorhabditis elegans, the fruit fly Drosophila melanogaster, the zebrafish Brachydanio rerio, the mouse Mus musculus, and the small flowering mustard plant Arabidopsis thaliana.

Physiology of organisms

See also: Physiology, Anatomy

Physiology studies the mechanical, physical, and biochemical processes of living organisms, by attempting to understand how all the structures function as a whole. The theme of “structure to function” is central to biology.

Physiological studies have traditionally been divided into plant physiology and animal physiology, but the principles of physiology are universal, regardless of the particular organism being studied. For example, what is learned about the physiology of yeast cells can also apply to other cells.
The field of animal physiology extends the tools and methods of human physiology to non-human animal species. Plant physiology also borrows techniques from both fields.

Anatomy is an important part of physiology and considers how organ systems in animals such as the nervous, immune, endocrine, respiratory, and circulatory systems function and interact. The study of these systems is shared with the medically oriented disciplines of neurology, immunology, and the like. The field of health science deals with both human and animal health.

Diversity and evolution of organisms

See also: Evolutionary biology, Botany, Zoology

Evolutionary biology is concerned with the origin and descent of species, and their change over time, i.e., their evolution.
Evolutionary biology is an inclusive field because it includes scientists from many traditional taxonomically oriented disciplines. For example, it generally includes scientists who may have a specialist training in particular organisms such as mammalogy, ornithology, or herpetology, but uses those organisms as systems to answer general questions in evolution. It also generally includes paleontologists who use fossils to answer questions about the mode and tempo of evolution, as well as theoreticians in areas such as population genetics and evolutionary theory. In the 1990s, developmental biology made a re-entry into evolutionary biology from its initial exclusion from the modern synthesis through the study of evolutionary developmental biology. Related fields which are often considered part of evolutionary biology are phylogenetics, systematics, and taxonomy.

The two major traditional taxonomically oriented disciplines are botany and zoology.
Botany is the scientific study of plants. It covers a wide range of scientific disciplines that study the growth, reproduction, metabolism, development, diseases, and evolution of plant life.
Zoology is the discipline that involves the study of animals, which includes the physiology of animals studied under various fields, including anatomy and embryology.
The common genetic and developmental mechanisms of animals and plants is studied in molecular biology, molecular genetics, and developmental biology. The ecology of animals is covered under behavioral ecology and other fields.

Classification of life

The dominant classification system is called Linnaean taxonomy, which includes ranks and binomial nomenclature. How organisms are named is governed by international agreements such as the International Code of Botanical Nomenclature (ICBN), the International Code of Zoological Nomenclature (ICZN), and the International Code of Nomenclature of Bacteria (ICNB). A fourth Draft BioCode was published in 1997 in an attempt to standardize naming in the three areas, but it has not yet been formally adopted. The International Code of Virus Classification and Nomenclature (ICVCN) remains outside the BioCode.

Interactions of organisms

See also: Ecology, Ethology, Behavior

Ecology studies the distribution and abundance of living organisms, and the interactions between organisms and their environment. The environment of an organism includes both its habitat, which can be described as the sum of local abiotic factors like climate and geology, as well as the other organisms which share its habitat.
Ecological systems are studied at several different levels—from individuals and populations to ecosystems and the biosphere level. Ecology is a multi-disciplinary science, drawing on many other branches of science.

Ethology studies animal behavior (particularly of social animals such as primates and canids), and is sometimes considered as a branch of zoology. Ethologists have been particularly concerned with the evolution of behavior and the understanding of behavior in terms of evolutionary thought. In one sense, the first modern ethologist was Charles Darwin, whose book The Expression of the Emotions in Animals and Men influenced many ethologists.

History of the word «biology»

The word «biology» derives from Greek and is generally rendered as «study of life.» Specifically, it is most commonly referenced as deriving from the Greek words βίος (bios), translated as «life,» and «λόγος (logos), a root word that may be translated as «reasoned account,» «logic,» «description,» «word,» or «human knowledge.»

The suffix «-logy» is common in science, in such words as geology, ecology, zoology, paleontology, microbiology, and so forth. This suffix is generally translated as «the study of.» Notably, the term ology is considered a back-formation from the names of these disciplines. Many references trace such words as «-logy» and «ology» from the Greek suffix -λογια (-logia), speaking, which comes from the Greek verb λεγειν (legein), to speak. The word ology is thus misleading as the “o” is actually part of the word stem that receives the -logy ending, such as the bio part of biology.

The word «biology» in its modern sense seems to have been introduced independently by Gottfried Reinhold Treviranus (Biologie oder Philosophie der Lebenden Natur, 1802) and by Jean-Baptiste Lamarck (Hydrogéologie, 1802). The word itself is sometimes said to have been coined in 1800 by Karl Friedrich Burdach, but it appears in the title of Volume 3 of Michael Christoph Hanov’s Philosophiae Naturalis Sive Physicae Dogmaticae: Geologia, Biologia, Phytologia Generalis et Dendrologia, published in 1766.

Notes

References

ISBN links support NWE through referral fees

• Margulis, L., and D. Sagan. Microcosmos: Four Billion Years of Evolution from our Microbial Ancestors. University of California Press, 1997.
• Margulis, L., and D. Sagan. Acquiring Genomes: A Theory of the Origins of Species. Basic Books, New York, 2002.
• Swenson, Rod. Order, evolution, and natural law: Fundamental relations in complex system theory. In Cybernetics and Applied Systems, edited by C.V. Negoita, 125-147. Marcel Dekker, New York, 1992.

Biology: The Study of Life

What is biology? Simply put, it is the study of life, in all of its grandeur. Biology concerns all life forms, from the very small algae to the very large elephant. But how do we know if something is living? For example, is a virus alive or dead? To answer these questions, biologists have created a set of criteria called the «characteristics of life.» 

Living things include both the visible world of animals, plants, and fungi as well as the invisible world of bacteria and viruses. On a basic level, we can say that life is ordered. Organisms have an enormously complex organization. We’re all familiar with the intricate systems of the basic unit of life, the cell.

Life can «work.» No, this doesn’t mean all animals are qualified for a job. It means that living creatures can take in energy from the environment. This energy, in the form of food, is transformed to maintain metabolic processes and for survival.

Life grows and develops. This means more than just replicating or getting larger in size. Living organisms also have the ability to rebuild and repair themselves when injured.

Life can reproduce. Have you ever seen dirt reproduce? I don’t think so. Life can only come from other living creatures.

Life can respond. Think about the last time you accidentally stubbed your toe. Almost instantly, you flinched back in pain. Life is characterized by this response to stimuli.

Finally, life can adapt and respond to the demands placed on it by the environment. There are three basic types of adaptations that can occur in higher organisms.

• Reversible changes occur as a response to changes in the environment. Let’s say you live near sea level and you travel to a mountainous area. You may begin to experience difficulty breathing and an increase in heart rate as a result of the change in altitude. These symptoms go away when you go back down to sea level.
• Somatic changes occur as a result of prolonged changes in the environment. Using the previous example, if you were to stay in the mountainous area for a long time, you would notice that your heart rate would begin to slow down and you would begin to breath normally. Somatic changes are also reversible.
• The final type of adaptation is called genotypic (caused by genetic mutation). These changes take place within the genetic makeup of the organism and are not reversible. An example would be the development of resistance to pesticides by insects and spiders.

In summary, life is organized, «works,» grows, reproduces, responds to stimuli and adapts. These characteristics form the basis of the study of biology.

Basic Principles of Biology

The foundation of biology as it exists today is based on five basic principles. They are the cell theory, gene theory, evolution, homeostasis, and laws of thermodynamics.

• Cell Theory: all living organisms are composed of cells. The cell is the basic unit of life.
• Gene Theory: traits are inherited through gene transmission. Genes are located on chromosomes and consist of DNA.
• Evolution: any genetic change in a population that is inherited over several generations. These changes may be small or large, noticeable or not so noticeable.
• Homeostasis: ability to maintain a constant internal environment in response to environmental changes.
• Thermodynamics: energy is constant and energy transformation is not completely efficient.

Subdiciplines of Biology
The field of biology is very broad in scope and can be divided into several disciplines. In the most general sense, these disciplines are categorized based on the type of organism studied. For example, zoology deals with animal studies, botany deals with plant studies, and microbiology is the study of microorganisms. These fields of study can be broken down further into several specialized sub-disciplines. Some of which include anatomy, cell biology, genetics, and physiology.