This glossary of biology terms is a list of definitions of fundamental terms and concepts used in biology, the study of life and of living organisms. It is intended as introductory material for novices.
Any non-living chemical or physical part of the environment that affects living organisms
and the functioning of ecosystems
, such as the atmosphere and water resources.
A process in which one substance permeates another. A fluid permeates or is dissolved by a liquid or solid. Skin absorption is a route by which substances can enter the body through the skin.
The process by which organisms diversify rapidly from an ancestral species
into a multitude of new forms, particularly when a change in the environment
makes new resources available, creates new challenges, or opens new niches
.
An organic compound derived from adenine
that functions as the major source of energy for chemical reactions inside living cells
. It is found in all forms of life and is often referred to as the "molecular currency" of intracellular energy transfer.
The study of organic particles which are passively transported by the air, including bacteria
, fungal spores, very small insects, pollen grains, and viruses
.
A form of speciation
which occurs when biological populations
of the same species
become isolated from each other to an extent that prevents or interferes with genetic interchange.
A class of organic compounds containing an amine group and a carboxylic acid group which function as the fundamental building blocks of proteins
and play important roles in many other biochemical processes.
A set of morphological
structures in different organisms which have similar form or function but were not present in the organisms' last common ancestor
. The cladistic term for the same phenomenon is homoplasy.
The process by which humans use animal breeding and plant breeding to selectively
control the development of particular phenotypictraits
in organisms by choosing which individual organisms will reproduce
and create offspring
. While the deliberate exploitation of knowledge about genetics
and reproductive biology
in the hope of producing desirable characteristics is widely practiced in agriculture
and experimental biology, artificial selection may also be unintentional and may produce unintended (desirable or undesirable) results.
An organism capable of producing complex organic compounds from simple substances present in its surroundings, generally by using energy from sunlight (as in photosynthesis
) or from inorganic chemical reactions (as in chemosynthesis
). Autotrophs do not need to consume another living organism in order to obtain energy or organic carbon, as opposed to heterotrophs
.
An enormous and diverse clade of microscopic, prokaryotic
, single-celled organisms which lack a true nucleus
. They represent one of the three fundamental biological domains
.
The inactive X chromosome in a female somatic cell, rendered inactive in a process called lyonization, in those species in which sex is determined by the presence of the Y (including humans) or W chromosome rather than the diploidy of the X or Z.
An organelle formed from a centriole, and a short cylindrical array of microtubules. Also called a basal granule, a kinetosome, and in older cytological literature, a blepharoplast.
A dark green to yellowish-brown fluid, produced by the liver of most vertebrates, which aids the digestion of lipids in the small intestine. Also called gall.
A formal system of classifying species
of living things by giving each a name composed of two parts, both of which use Latin grammatical forms, although they can be based on words from other languages.
The process of catalysis in biological systems. In biocatalytic processes, natural catalysts, such as protein enzymes, perform chemical transformations on organic compounds.
The study of the distribution of species and ecosystems in geographic space and through geological time. Organisms and biological communities often vary in a regular fashion along geographic gradients of latitude, elevation, isolation and habitat area.
Organic matter derived from living or recently living organisms. Biomass can be used as a source of energy and it most often refers to plants or plant-based materials which are not used for food or feed, and are specifically called lignocellulosic biomass.
Any very large ecological
area on the Earth's surface containing fauna and flora (animals and plants) adapting to their environment. Biomes are often defined by abiotic factors
such as climate, topographical relief, geology, soils, and water resources.
The study of the structure and function of biological systems by means of the methods of "mechanics", which is the branch of physics involving analysis of the actions of forces.
The pursuit of answers to medical questions. These investigations lead to discoveries, which in turn lead to the development of new preventions, therapies, and cures for problems in human and veterinary health. Biomedical research generally takes two forms: basic science and applied research.
Biotechnology is the use of living systems and organisms to develop or make products, or "any technological application that uses biological systems, living organisms or derivatives thereof, to make or modify products or processes for specific use" (UN Convention on Biological Diversity).
A body fluid that circulates in humans and other vertebrate animals and is generally responsible for delivering necessary substances such as oxygen and nutrients between the cells and tissues of the body and transporting metabolic waste products away from those same cells and tissues.
A semipermeable membrane separating the blood from the cerebrospinal fluid, and constituting a barrier to the passage of cells, particles, and large molecules.
The Calvin cycle, light-independent reactions, bio synthetic phase, dark reactions, or photosynthetic carbon reduction (PCR) cycle[1] of photosynthesis are the chemical reactions that convert carbon dioxide and other compounds into glucose. These reactions occur in the stroma, the fluid-filled area of a chloroplast outside the thylakoid membranes. These reactions take the products (ATP and NADPH) of light-dependent reactions and perform further chemical processes on them. There are three phases to the light-independent reactions, collectively called the Calvin cycle: carbon fixation, reduction reactions, and ribulose 1,5-bisphosphate (RuBP) regeneration.
The basic structural and functional unit of all living organisms
, and the smallest functional unit of life. A cell may exist as an independent, self-replicating unit (as in the case of unicellular organisms
), or in cooperation with other cells, each of which may be specialized for carrying out particular functions within a larger multicellular organism
. Cells consist of cytoplasm
enclosed within a cell membrane
and sometimes a cell wall
, and serve the fundamental purpose of separating the controlled environment in which biochemical processes take place from the outside world. Most cells are visible only under a microscope.
The branch of biology that studies the structure and function of living cells
, including their physiological
properties, metabolic
processes, chemical composition, life cycle
, the organelles
they contain, and their interactions with their environment. This is done at both microscopic and molecular
levels.
A tough, often rigid structural barrier surrounding certain types of cells
(such as in fungi
, plants
, and most prokaryotes
) that is immediately external to the cell membrane
.
A framework for understanding the movement of genetic information between information-carrying biopolymers within biological systems. Popularly (though simplistically) stated as "DNA
makes RNA
and RNA makes protein
", the principle attempts to capture the notion that the transfer of genetic information only naturally occurs between certain classes of molecules and in certain directions.
An organelle that is the main place where cell microtubules get organized, occurring only in plant and animal cells and regulating the cell division cycle.
A chemical substance consisting of two or more different chemically bondedelements, with a fixed ratio determining the composition. The ratio of each element is usually expressed by a chemical formula.
The state in which both reactants and products are present in concentrations which have no further tendency to change with time in a chemical reaction.
A branch of the physical sciences that studies the composition, structure, properties, and change of matter. Chemical interactions underlie all biological processes.
Organelles, specialized subunits, in plant and algal cells, main role of which is to conduct photosynthesis, where the photosynthetic pigment chlorophyll captures the energy from sunlight and converts and stores it in the energy-storage molecules ATP and NADPH while freeing oxygen from water.
An organic molecule, a sterol, a type of lipid molecule, and biosynthesized by all animal cells because it is an essential structural component of all animal cell membranes—essential to maintain both membrane structural integrity and fluidity.
Also called the Krebs cycle and tricarboxylic acid cycle (TCA).
A series of chemical reactions used by all aerobic organisms to generate energy through the oxidation of acetyl-CoA derived from carbohydrates, fats and proteins into carbon dioxide and chemical energy in the form of guanosine triphosphate (GTP). In addition, the cycle provides precursors of certain amino acids as well as the reducing agent NADH that is used in numerous other biochemical reactions. Its central importance to many biochemical pathways suggests that it was one of the earliest established components of cellular metabolism and may have originated abiogenically.
The process of producing similar populations of genetically identical individuals that occurs in nature when organisms such as bacteria, insects or plants reproduce asexually.
The scientific study of nature and 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.
A mechanism that happens in nature and is mimicked in industry and engineering, in which there is a crossover of some property, usually heat or some component, between two flowing bodies flowing in opposite directions to each other.
One of the four main nucleotide bases found in DNA and RNA, along with adenine, guanine, thymine, and uracil (in RNA); it is a pyrimidine derivative, with a heterocyclic aromatic ring and two substituents attached (an amine group at position 4 and a keto group at position 2).
A cytoskeleton is present in the cytoplasm
of all cells
, including bacteria, and archaea. It is a complex, dynamic network of interlinking protein filaments that extends from the cell nucleus to the cell membrane.[3] The cytoskeletal systems of different organisms are composed of similar proteins. In eukaryotes, the cytoskeletal matrix is a dynamic structure composed of three main proteins, which are capable of rapid growth or disassembly dependent on the cell's requirements.[4]
The genetic contribution of an individual to the next generation's gene pool relative to the average for the population, usually measured by the number of offspring or close kin that survive to reproductive age.
Deciduous means "falling off at maturity" or "tending to fall off", and it is typically used in order to refer to trees or shrubs that lose their leaves seasonally (most commonly during autumn) and to the shedding of other plant structures such as petals after flowering or fruit when ripe.
A process in which proteins or nucleic acids lose the quaternary, tertiary and secondary structure which is present in their native state, by application of some external stress or compound such as a strong acid or base, a concentrated inorganic salt, or an organic solvent.
A microbially facilitated process of nitrate reduction (performed by a large group of heterotrophic facultative anaerobic bacteria) that may ultimately produce molecular nitrogen (N2) through a series of intermediate gaseous nitrogen oxide products. Part of the nitrogen cycle.
A nucleic acidpolymer
that serves as the fundamental hereditary material in all living organisms. A set of four bases is used in the nucleotide sequences which comprise each DNA molecule: adenine
(abbreviated A), cytosine
(C), guanine
(G), and thymine
(T); these four bases are individually attached to a sugar-phosphate complex to form a complete nucleotide.
The process of reversing the charge across a cell membrane
(such as that of a neuron), thereby causing an action potential
. In depolarization, the inside of the membrane, which is normally negatively charged, becomes positive and the outside becomes negative. This is brought about by positive sodium ions rapidly passing into the axon.
The branch of biology that studies the processes by which living organisms grow and develop over time. The field may also encompass the study of reproduction
, regeneration
, metamorphosis
, and the growth and differentiation of stem cells
in mature tissues.
The replication of a DNA
molecule; the process of producing two identical copies from one original DNA molecule, in which the double helix is unwound and each strand acts as a template for the next strand; nucleotide bases are matched to synthesize the new partner strands.
A motor protein (also called molecular motor or motor molecule) in cells which converts the chemical energy contained in ATP into the mechanical energy of movement.
The efficiency with which energy is transferred from one trophic level to the next. It is determined by a combination of efficiencies relating to organismic resource acquisition and assimilation in an ecosystem
. Primary production occurs in autotrophic
organisms of an ecosystem.
An ecological pyramid (also trophic pyramid, eltonian pyramid, energy pyramid, or sometimes food pyramid) is a graphical representation designed to show the biomass or bio productivity at each trophic level in a given ecosystem. Biomass is the amount of living or organic matter present in an organism.
The scientific analysis and study of interactions between organisms
and their environment
. It is an interdisciplinary field that includes biology, geography, and Earth science.
In evolutionary ecology, a genetically distinct geographic variety, population
, or race within a species
which is adapted to specific environmental conditions.
The outermost layer of cells or tissue of an embryo
in early development, or the parts derived from this, which include the epidermis, nerve tissue, and nephridia.
An organism in which internal physiological sources of heat are of relatively small or quite negligible importance in controlling body temperature. Colloquially, these organisms often referred to as "cold-blooded".
Conducted or conducting outwards or away from something (for nerves, the central nervous system; for blood vessels, the organ supplied). Contrast afferent.
The organic vessel containing the zygote
in which an animal embryo
develops until it can survive on its own, at which point the developing organism emerges from the egg in a process known as hatching.
A gradient of electrochemical potential, usually for an ion
that can move across a membrane. The gradient consists of two parts: the electrical potential and the difference in chemical concentration across the membrane.
The range of all possible frequencies of electromagnetic radiation. When referring to an object, the electromagnetic spectrum is the characteristic distribution of electromagnetic radiation emitted or absorbed by that particular object.
An electron acceptor is a chemical entity that accepts electrons transferred to it from another compound. It is an oxidizing agent that, by virtue of its accepting electrons, is itself reduced in the process.
electron carrier. Any of various molecules that are capable of accepting one or two electrons from one molecule and donating them to another in the process of electron transport. As the electrons are transferred from one electron carrier to another, their energy level decreases, and energy is released.
An electron donor is a chemical entity that donates electrons to another compound. It is a reducing agent that, by virtue of its donating electrons, is itself oxidized in the process.
The electron microscope is a type of microscope that uses a beam of electrons to create an image of the specimen. It is capable of much higher magnifications and has a greater resolving power than a light microscope, allowing it to see much smaller objects in finer detail.
The site in a mitochondrion of oxidative phosphorylation in eukaryotes. The NADH and succinate generated by the citric acid cycle are oxidized, providing energy to power ATP synthase. Photosynthetic electron transport chain of the thylakoid membrane.
The branch of biology that studies the development of gametes
(sex cells), fertilization, and development of embryos
and fetuses
. Additionally, embryology involves the study of congenital disorders that occur before birth.
Endangered species are threatened by factors such as habitat loss, hunting, disease and climate change, and usually, endangered species, have a declining population or a very limited range.
The ecological state of an organism or species being unique to a defined geographic location, such as an island, nation, country, habitat type, or other defined zone. Organisms are said to be endemic to a place if they are indigenous to it and found nowhere else.
The collection of glands
that produce hormones
which regulate metabolism
, growth and development, tissue function, and a wide variety of other biological processes.
A form of active transport
in which a cell transports molecules such as proteins into the cell's interior by engulfing them in an energy-consuming process.
One of the three primary germ layers in the very early human embryo
. The other two layers are the ectoderm
(outside layer) and mesoderm
(middle layer), with the endoderm being the innermost layer.
A type of organelle found in eukaryotic cells that forms an interconnected network of flattened, membrane-enclosed sacs or tube-like structures known as cisternae.
An evolutionary theory of the origin of eukaryotic cells from prokaryotic organisms, first articulated in 1905 and 1910 by the Russian botanist Konstantin Mereschkowski, and advanced and substantiated with microbiological evidence by Lynn Margulis in 1967.
An organism that maintains its body at a metabolically favorable temperature, largely by the use of heat set free by its internal bodily functions instead of relying almost purely on ambient heat.
the branch of biology concerned with the relations between organisms and their environment. bionomics, ecology. biological science, biology - the science that studies living organisms. palaeoecology, paleoecology - the branch of ecology that studies ancient ecology.
Enzymes are biological molecules (proteins) that act as catalysts and help complex reactions occur everywhere in life. Let's say you ate a piece of meat. Proteases would go to work and help break down the peptide bonds between the amino acids.
Epidemiology is the study and analysis of the patterns, causes, and effects of health and disease conditions in defined populations. It is the cornerstone of public health, and shapes policy decisions and evidence-based practice by identifying risk factors for disease and targets for preventive healthcare.
A sub-field of genetics
that studies cellular and physiological phenotypic trait variations caused by external or environmental factors which affect how cells expressgenes
, as opposed to those caused by changes in the DNA
sequence.
An organism that grows on the surface of a plant and derives its moisture and nutrients from the air, rain, marine environments or from debris accumulating around it.
The scientific study of non-human animal behaviour (i.e. excluding human behaviour) and usually with a focus on behaviour under natural conditions, and viewing behaviour as an evolutionarily adaptive trait.
Evolutionary biology is the subfield of biology that studies the evolutionary processes that produced the diversity of life on Earth starting from a single origin of life. These processes include the descent of species, and the origin of new species.
A form of active transport and bulk transport in which a cell transports molecules out of the cell by expelling them through an energy-dependent process.
It is exhibited when the rate of change of the value of a mathematical function is proportional to the function's current value, resulting in its value at any time being an exponential function of time.
An organism which is capable of producing energy through aerobic respiration and then switching to anaerobic respiration depending on the amounts of oxygen and fermentable material in the environment.
A family of proteins
that act as molecular switches inside cells
, and are implicated in transmitting signals from a diversity of stimuli outside a cell to its interior.
Any segment of DNA
that contains the information necessary to produce a functional RNA
and/or protein
product in a controlled manner. Genes are often considered the fundamental molecular units of heredity
. The transmission of genes from a parent cell or organism to its offspring
is the basis of the inheritance of phenotypic traits
.
Variations of genomes between members of species, or between groups of species thriving in different parts of the world as a result of genetic mutation. Genetic diversity in a population or species is a result of new gene combinations (e.g. crossing over of chromosomes), genetic mutations, genetic drift, etc.
An organ found in the digestive tract of some animals, including archosaurs (pterosaurs, crocodiles, alligators, and dinosaurs, including birds), earthworms, some gastropods, some fish, and some crustaceans.
The passing on of phenotypictraits
from parents to their offspring
, either through sexual
or asexual reproduction
. Offspring cells and organisms are said to inherit the genetic information of their parents.
Any member of a class of signaling molecules produced by glands in multicellular
organisms that are transported by the circulatory system to target distant organs to regulate physiology and behaviour.
Any living organism that harbors another living organism (known as a "guest" or symbiont
), whether the guest is parasitic
, mutualistic, or commensalist in its interactions with the host. The guest typically receives shelter and nourishment from the host.
An organic compound consisting entirely of hydrogen and carbon atoms. Hydrocarbons from which one hydrogen atom has been removed are functional groups called hydrocarbyls.
The branch of biology devoted to the study of fish, including bony fishes (Osteichthyes), cartilaginous fish (Chondrichthyes), and jawless fish (Agnatha).
Glycoprotein molecules produced by plasma cells (white blood cells) which act as a critical part of the immune response by specifically recognizing and binding to particular antigens, such as bacteria or viruses, and aiding in their destruction. Also known as antibodies.
The invasion of an organism's cells or tissues by a disease
-causing pathogen
, its growth and/or multiplication, and the reaction of the host
organism to the infectious agent and the toxins
it produces. The variety of biological pathogens capable of causing infections includes certain bacteria
, viruses
, fungi
, protists
, parasitic worms, and arthropods.
Insulin helps keeps your blood sugar level from getting too high (hyperglycemia) or too low (hypoglycemia). ... After you eat food and your blood sugar level rises, cells in your pancreas (known as beta cells) are signaled to release insulin into your bloodstream.
A group of signaling proteins made and released by host cells in response to the presence of several pathogens, such as viruses, bacteria, parasites, and also tumor cells. In a typical scenario, a virus-infected cell will release interferons causing nearby cells to heighten their antiviral defenses.
The complete transfer of valence electron(s) between atoms. It is a type of chemical bond that generates two oppositely charged ions. In ionic bonds, the metal loses electrons to become a positively charged cation, whereas the nonmetal accepts those electrons to become a negatively charged anion.
A molecule with the same chemical formula as another molecule, but with a different chemical structure. That is, isomers contain the same number of atoms of each element, but have different arrangements of their atoms.
Refers to two solutions having the same osmotic pressure across a semipermeable membrane. This state allows for the free movement of water across the membrane without changing the concentration of solutes on either side.
A distinct juvenile form many animals
undergo before metamorphosis
into adults. Animals with indirect development, such as insects, amphibians, or cnidarians, typically have a larval phase of their life cycle
.
The principle, originally formulated by Gregor Mendel, stating that when two or more characteristics are inherited, individual hereditary factors assort independently during gamete production, giving different traits an equal opportunity of occurring together.
A colourless cell which circulates in the blood and body fluids and is involved in counteracting foreign substances and disease; sometimes called a white blood cell. There are several types, all amoeboid cells with a nucleus, including lymphocytes, granulocytes, and monocytes.
The fibrous connective tissue that connects bones to other bones and is also known as articular ligament, articular larua, fibrous ligament, or true ligament.
Any set of one or more genes
which are sufficiently close together on the same chromosome that they are very unlikely to assort independently and therefore are usually inherited together.
A substance that is insoluble in water and soluble in alcohol, ether, and chloroform. Lipids are an important component of living cells. Together with carbohydrates and proteins, lipids are the main constituents of plant and animal cells. Cholesterol and triglycerides are lipids.
A biochemical assembly that contains both proteins and lipids, bound to the proteins, which allow fats to move through the water inside and outside cells. The proteins serve to emulsify the lipid molecules.
Mitosis and cytokinesis together define the mitotic (M) phase of an animal cell cycle – the division of the mother cell into two daughter cells, genetically identical to each other and to their parent cell.
Evolution on a scale of separated gene pools. Macroevolutionary studies focus on change that occurs at or above the level of species, in contrast with microevolution, which refers to smaller evolutionary changes (typically described as changes in allele frequencies) within a species or population.
A very large molecule, such as a protein, commonly created by polymerization of smaller subunits (monomers). They are typically composed of thousands or more atoms.
Nutrients needed in large amounts which provide calories or energy. Nutrients are substances needed for growth, metabolism, and for other body functions. There are three basic types of macronutrients: fats, proteins, and carbohydrates.
A kind of swallowing cell, which means it functions by literally swallowing up other particles or smaller cells. Macrophages engulf and digest debris (like dead cells) and foreign particles through the process of phagocytosis, so macrophages act like scavengers.
The study of mammals, a class of vertebrates with characteristics such as homeothermic metabolism, fur, four-chambered hearts, and complex nervous systems.
The study of organisms in the ocean or other marine bodies of water. Given that in biology many phyla, families and genera have some species that live in the sea and others that live on land, marine biology classifies species based on the environment rather than on taxonomy.
A cell filled with basophil granules, found in numbers in connective tissue and releasing histamine and other substances during inflammatory and allergic reactions.
A specialized type of cell division
in which a dividing parent cell proceeds through two consecutive divisions, ultimately producing four genetically unique daughter cells in each of which the chromosome
number is half of that in the original parent cell. This process is exclusive to cells of the sex organs in sexually reproducingeukaryotes
, where it serves the purpose of generating gametes
such as eggs
, sperm
, or spores
.
When a nerve or muscle cell is at "rest", its membrane potential is called the resting membrane potential. In a typical neuron, this is about –70 millivolts (mV). The minus sign indicates that the inside of the cell is negative with respect to the surrounding extracellular fluid.
The third phase of mitosis, in which duplicated genetic material carried in the nucleus of a parent cell is separated into two identical daughter cells. During metaphase, the cell's chromosomes align themselves in the middle of the cell through a type of cellular "tug of war".
The study of microscopic organisms, such as bacteria, viruses, archaea, fungi and protozoa. This discipline includes fundamental research on the biochemistry, physiology, cell biology, ecology, evolution and clinical aspects of microorganisms, including the host response to these agents.
The smallest particle in a chemical element or compound that has the chemical properties of that element or compound. Molecules are made up of atoms that are held together by chemical bonds. These bonds form as a result of the sharing or exchange of electrons among atoms.
The branch of biology concerning biological activity at the molecular level. The field of molecular biology overlaps with biology and chemistry and in particular with genetics and biochemistry.
A neuron whose cell body is situated in the motor cortex, brainstem or the spinal cord, and whose axon (fiber) projects to the spinal cord or outside of the spinal cord to directly or indirectly control effector organs, mainly muscles and glands.
The branch of biology concerned with the study of fungi, including their genetic and biochemical properties, their taxonomy and their use to humans as a source for tinder, medicine, food, and entheogens, as well as their dangers, such as poisoning or infection.
A process in nature in which organisms possessing certain genotypic
characteristics that make them better adjusted to an environment tend to survive, reproduce, increase in number or frequency, and therefore, are able to transmit and perpetuate their essential genotypic qualities to succeeding generations.
The role and position an organism or taxon fills within its environment; how it meets its needs for food and shelter, how it survives, and how it reproduces. A species' niche includes all of its interactions with the biotic and abiotic factors of its environment.
The nitrogen-containing biological compounds that form nucleosides, which in turn are components of nucleotides, with all of these monomers constituting the basic building blocks of nucleic acids.
An organic compound which serves as the fundamental monomer
used in the construction of nucleic acid
polymers, such as DNA
and RNA
, both of which are essential biomolecules within all living organisms.
The branch of zoology that concerns the study of birds. Etymologically, the word "ornithology" derives from the ancient Greek ὄρνις ornis ("bird") and λόγος logos ("rationale" or "explanation").
The spontaneous net movement of solvent molecules through a semipermeable membrane into a region of higher solute concentration, in the direction that tends to equalize the solute concentrations on the two sides.
The study of the history of life on Earth as reflected in the fossil record. Fossils are the remains or traces of organisms (plants, animals, fungi, bacteria and other single-celled living things) that lived in the geological past and are preserved in the crust of the Earth.
The study of parasites, their hosts, and the relationship between them. As a biological discipline, the scope of parasitology is not determined by the organism or environment in question, but by their way of life.
A medical specialty that is concerned with the diagnosis of disease based on the laboratory analysis of bodily fluids such as blood and urine, as well as tissues, using the tools of chemistry, clinical microbiology, hematology and molecular pathology.
A numeric scale used to specify the acidity or basicity (alkalinity) of an aqueous solution. It is roughly the negative of the logarithm to base 10 of the concentration, measured in units of moles per liter, of hydrogen ions.
The science of drug action on biological systems. In its entirety, it embraces knowledge of the sources, chemical properties, biological effects and therapeutic uses of drugs.
The composite of an organism's observable features or traits, such as its morphology, development, biochemical or physiological properties, behavior, and products of behavior.
The transfer of pollen from a male part of a plant to a female part of a plant, enabling later fertilisation and the production of seeds, most often by an animal or by wind.
A technique used in molecular biology to amplify a single copy or a few copies of a segment of DNA
across several orders of magnitude, generating thousands to millions of copies of a particular DNA
sequence.
A subfield of ecology that deals with the dynamics of species populations and how these populations interact with the environment. It is the study of how the population sizes of species change over time and space. Also called autoecology.
The application of the principles of biology to the study of physiological, genetic, and developmental mechanisms of behavior in humans and other animals. Also called behavioral neuroscience, biological psychology, and biopsychology.
A field of scientific study that is based on the hypothesis that social behavior has resulted from evolution and attempts to explain and examine social behavior within that context.
The basic unit of classification and a taxonomic rank, as well as a unit of biodiversity, but it has proven difficult to find a satisfactory definition.
Any close and long-term biological interaction between two different biological organisms, regardless of the nature or degree of the effect on either organism. Examples include mutualism, commensalism, and parasitism.
An interdisciplinary branch of biology and engineering. The subject combines various disciplines from within these domains, such as biotechnology, evolutionary biology, molecular biology, systems biology, biophysics, computer engineering, and genetic engineering.
The scientific study of biodiversity. It is concerned with the discovering and naming of new species of organisms (nomenclature) and arranging these taxa into classification schemes (taxonomy). A large part of modern systematics concerns establishing the evolutionary relationships among various taxa (phylogenetics) using methods of comparative biology (e.g. physiology, behavior, biochemistry, morphology, genetics) and statistical analysis.
Transcription is the first step of gene expression, in which a particular segment of DNA is copied into RNA (mRNA) by the enzyme RNA polymerase. Both RNA and DNA are nucleic acids, which use base pairs of nucleotides as a complementary language.
A valence electron is an electron that is associated with an atom, and that can participate in the formation of a chemical bond; in a single covalent bond, both atoms in the bond contribute one valence electron in order to form a shared pair.
The retention during the process of evolution of genetically determined structures or attributes that have lost some or all of their ancestral function in a given species
.
A submicroscopic, infectious, parasitic particle of genetic material contained in a protein coat and which replicates only inside the living cell of a host
organism.
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