Category: Biology Dictionary

Zygote : A eukaryotic cell formed by a fertilization event between two gametes.

Zygospore : A diploid reproductive stage in the life cycle of many fungi and protists.

Zoology : The branch of biology that studies the animal kingdom, including the structure, embryology, evolution, classification, habits, and geographical distribution of all animals, both living and extinct, and how they interact with their ecosystems.

Yolk : The nutrient-bearing portion of the egg whose primary function is to supply food for the development of the embryo.

Xylem : A type of plant tissue responsible for the transport of water from roots to aerial parts of the plant.

Xanthophyll : A yellow-colored photosynthetic pigment.

Wood : The inner layer of the stems of woody plants such as trees and shrubs, composed of xylem.

Whole genome sequencing : The process of determining the complete DNA sequence of a particular organism’s entire genome at a single time.

White blood cell : See leukocyte.

Virus : 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.

Virology : The branch of biology that studies viruses.

Vestigiality : 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.

Vesicle : A small structure within or sometimes external to a cell, consisting of fluid enclosed by a lipid bilayer.

Vegetative reproduction : Any type of asexual reproduction performed by an organism which is nonetheless capable of sexual reproduction. The term is used primarily for plants.

Vasodilation : The widening of blood vessels.

Vacuole : A membrane-bound organelle which is present in all plant and fungal cells and some protist, animal, and bacterial cells.

Uterus : A major female hormone-responsive secondary sex organ of the reproductive system in humans and most other mammals.

Urine : A liquid byproduct of metabolism in humans and in many animals.

Urea : An organic compound with chemical formula CO(NH2)2.

Uracil : One of the four nucleobases in the nucleic acid of RNA that are represented by the letters A, G, C and U.

Unicellular : Having or consisting of only one cell, as opposed to being multicellular.

Uncoating : The decomposition of a viral capsid. An informal and simplified description of the way a virus infectious material enters the cell, usually appearing in light science material for the general public.

Tumor : Also called a neoplasm.

Trophic level : The position an organism occupies in a food chain.

Translation : The process by which ribosomes in the cytoplasm or endoplasmic reticulum synthesize proteins following the transcription of DNA to RNA in the cell’s nucleus.

Transcription : The first step of gene expression, in which a particular segment of DNA is copied into RNA by the enzyme RNA polymerase. Both RNA and DNA are nucleic acids, which use complementary base pairs of nucleotides as a common language.

Thymine  : One of the four nucleobases used in the nucleic acid DNA (but not in RNA). It is represented in DNA sequences by the letter T.

Taxon :(pl.) taxa

A group of one or more populations of an organism or organisms used by taxonomists to classify organisms into discrete, convenient, and identifiable units.

T cell : A type of lymphocyte that plays a central role in cell-mediated immunity.

Systems biology : A branch of biology concerned with the computational and mathematical analysis of complex biological systems. It is an interdisciplinary field which combines elements of systems theory and applied mathematics with theoretical biology, with a primary aim to discover and model the emergent properties of interacting biological entities.

Strain : A genetic variant, subtype, or culture identified as a distinct taxonomic subdivision within a species. The term is most commonly used to identify particular types of bacteria and viruses.

Stem cell : A type of undifferentiated or partially undifferentiated cell that is capable of differentiating into other types of specialized cells and also capable of dividing to produce more of the same type of stem cell. Stem cells are the earliest type of cell in a cell lineage.

Speciation : The evolutionary process by which populations of organisms evolve to become distinct species, typically via reproductive isolation.

Species : The basic unit of biological classification and the narrowest of the canonical taxonomic ranks, as well as a unit of biodiversity. Species are traditionally distinguished on the basis of reproductive compatibility, though achieving a satisfactory definition that is universally applicable to all life has proven difficult, since many organisms classified as distinct “species” are capable of interbreeding with different (albeit closely related) species, generating hybrids.

Soil biology : The study of microbial and faunal activity and ecology in soil.

Sociobiology : A branch of biology that is based on the hypothesis that social behavior has resulted from evolution and which attempts to explain and examine social behavior within that context.

Sociality : The degree to which individuals in an animal population tend to associate in social groups and form cooperative societies.

Sexual reproduction : A type of reproduction in which cells from two parents unite to form the first cell of a new organism.

Sessile : 1.  Generally, lacking motility or means of self-locomotion; immobile or incapable of movement. Sessile organisms may move via external forces such as wind or water currents but are more often permanently fixed to a solid object such as a rock, soil, or another organism.2.  In botany, the property of a plant or plant part that is attached directly by its base to an object or another plant part, i.e. without an intervening stem, stalk, or petiole.

Selective breeding : See artificial selection.

Seed : The embryo, enclosed in a protective outer covering, of certain types of plants.

Sclerenchyma : A type of tissue in which cells have thick lignified secondary walls and often die when mature.

RNA polymerase : A member of a family of enzymes that are essential to life: they are found in all organisms and many viruses.

RNA : See ribonucleic acid.

Ribosome : A complex molecular machine, found within all living cells, that serves as the site of biological protein synthesis.

Ribonucleic acid (RNA) : A nucleic acid polymer composed of a series of ribonucleotides which incorporate a set of four nucleobases: adenine (A), guanine (G), cytosine (C), and uracil (U). Closely related to DNA, RNA molecules serve in a wide variety of essential biological roles, including coding, decoding, regulating, and expressing genes, as well as functioning as signaling molecules.

Reproductive biology : The branch of biology that studies the various types and mechanisms of reproduction used by living organisms, typically with special emphasis on cell division, fertility, endocrinology, and/or the tissues, organs, and systems involved in reproduction.

Reproduction : Also called procreation or breeding.

The biological process by which one or more new individual organisms (known as offspring) is produced from an existing parent organism. Reproduction is a defining characteristic of all life, and every individual organism exists as the result of a reproductive event. There are two general methods by which reproduction takes place: sexual or asexual.

Regeneration :The process of renewal, restoration, and growth that makes genomes, cells, organisms, and ecosystems resilient to natural fluctuations or events that cause disturbance or damage. For example, many organisms are capable of regenerating tissues and even entire body parts if they are lost or destroyed.

Psychobiology :Also called behavioral neuroscience, biological psychology, and biopsychology.

The application of the principles of biology to the study of physiological, genetic, and developmental mechanisms of behavior in humans and other animals.

Protein : A polypeptide chain of amino acids. It is a body-building nutrient.

Prokaryote : A type of organism which does not have a true nucleus.

Progesterone : An endogenous steroid and progestogen sex hormone which plays a critical role in the menstrual cycle, pregnancy, and embryogenesis in humans and other animal species.

Progeny : Any genetic descendant or offspring.

Primer : A short strand of RNA or DNA that serves as a starting point for DNA synthesis.

Predation : A biological interaction in which a predator kills and eats its prey.

Population ecology : Also called autoecology.

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.

Population biology : The study of populations of organisms, especially the regulation of population size, life history traits such as clutch size, and extinction.

Population : All the organisms of the same group or species that live in a particular geographical area and are capable of interbreeding.

Polyploidy : Having or containing more than two complete sets of chromosomes.

Polymerase chain reaction (PCR) : 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.

Polymer : A large macromolecule composed of many repeated subunits.

Pollination : 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. Pollen is most commonly transported by animals or by wind.

Plasmolysis : The process in which cells lose water in a hypertonic solution.

Placebo : A substance or treatment of no intended therapeutic value.

Phytopathology : The science of diagnosing and managing plant diseases.

Phytochemistry : The study of phytochemicals, which are chemicals derived from plants.

Physiology : The branch of biology dealing with the functions and activities of living organisms and their parts, including all physical and chemical processes.

Phylum : A taxonomic rank or level of classification below kingdom and above class; in botany, the term division is commonly used in place of phylum.

Photosynthesis : The process by which nearly all plants and some algae and bacteria convert the energy of sunlight into chemical energy, which is used to synthesize carbohydrates such as sugars from carbon dioxide and water; these carbohydrates are stored as food, and the energy within them is later released to fuel metabolic activities. Organisms that perform photosynthesis are therefore autotrophs. Photosynthesis supplies the majority of the energy necessary for life on Earth.

Pheromone : A secreted or excreted chemical factor that triggers a social response in members of the same species. Pheromones are analogous to hormones acting outside the body of the secreting individual to impact the behavior of receiving individuals.

Phenotype : The composite of an organism’s observable features or traits, such as its morphology, development, biochemical or physiological properties, behavior, and products of behavior.

Pharmacology : 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.

pH : 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.

Pathology : 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.

Pathogen : In the broadest sense, anything that can produce disease, though the term is most commonly used to refer specifically to an infectious microscopic organism such as a virus, bacterium, protozoan, or another microbial agent which causes disease for a host organism by invading the host’s tissues.

Pathobiology : The study or practice of pathology with greater emphasis on the biological than on the medical aspects.

Parasitology : 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.

Paleontology : The study of the history of life on Earth as reflected in the fossil record. Fossils are the remains or traces of organisms that lived in the geological past and have been preserved in the Earth’s crust.

Osmosis: 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.

Ornithology : The branch of zoology that concerns the study of birds.

Organism : A contiguous living system.

 Organ : A collection of tissues joined in a structural unit to serve a common function.

Nucleotide : 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.

Nucleolus : The largest structure within the nucleus of eukaryotic cells.

Nucleoid : An irregularly shaped region within the cell of a prokaryote that contains all or most of the genetic material, called the genophore.

Nucleobase : 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.

Nucleic acid sequence : A succession of letters that indicate the order of nucleotides forming alleles within a DNA or RNA molecule.

Nucleic acid : The biopolymers, or small biomolecules, essential to all known forms of life .

Niche : 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.

Neurotransmitter : An endogenous compound that enable neurotransmission.

Neuron : An electrically excitable cell that receives, processes, and transmits information through electrical and chemical signals.

Neurobiology : Also called neuroscience.

The scientific study of the nervous system.

Natural selection : 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.

Myosin : A superfamily of motor proteins best known for their roles in muscle contraction and in a wide range of other motility processes in eukaryotes.

Myofibril : A basic rod-like unit of a muscle cell.

Mycology : 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.

Multicellular : Having or consisting of more than one cell, as opposed to being unicellular.

Mucous membrane : A membrane that lines various cavities in the body and covers the surface of internal organs.

Motor neuron: A neuron whose cell body is situated in the motor cortex, brain stem, 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.