Glossary of Biology Terms & Definitions
Contained in this glossary of biology terms is a list of definitions of fundamental terms and concepts used in biology, the branch of science that deals with the study of living things.
a
- abscission - Abscission is the shedding of various parts of an organism, such as a plant dropping a leaf, fruit, flower, or seed.
- absorption - Absorption is the movement of digested food molecules from the digestive system into the blood (glucose and amino acids) and lymph (fatty acids and glycerol).…
- active transport - Active transport moves molecules and ions from a region of lower concentration to a region of higher concentration with the help of energy in the…
- aerobe - An aerobic organism or aerobe is an organism that can survive and grow in an oxygenated environment. The ability to exhibit aerobic respiration may yield…
- afforestation - Afforestation is the establishment of a forest or stand of trees (forestation) in an area where there was no recent tree cover.
- amnion - This is a membrane in reptiles, birds and mammals, forming a fluid-filled cavity (the amniotic sac) that encloses the embryo. The amniotic sac and the…
- anaemia - Anaemia is when the body does not have enough healthy red blood cells or haemoglobin. Red blood cells and haemoglobin (the molecule in red blood…
- anaerobe - An anaerobic organism or anaerobe is any organism that does not require molecular oxygen for growth. It may react negatively or even die if free…
- antidiuretic hormone - Antidiuretic hormone (ADH) is a hormone that helps your kidneys manage the amount of water in your body ADH is a substance produced naturally in…
- apical dominance - This is the process in which the shoot apex of a plant grows faster and prevents the growth of lateral buds present at the lower…
- assimilation - 1. the process of taking in and fully understanding information or ideas. 2. the absorption and digestion of food or nutrients by the body or…
- ATP - Adenosine triphosphate (ATP) is an energy-carrying, found in the cells of all living things. It captures chemical energy from the breakdown of food molecules and…
- autotroph - An autotroph is an organism that can produce its own food using light, water, carbon dioxide, or other chemicals. It feeds itself, without the assistance…
c
- chitin - Chitin is the most abundant amino polysaccharide polymer occurring in nature, and is the building material that gives strength to the exoskeletons of crustaceans, insects,…
- chorion - The chorion is a membrane that surrounds a developing fetus in conjunction with the amnion. The chorion eventually forms the fetal placenta. The placenta provides…
- concentration gradient - A concentration gradient occurs in a solution or gas when the concentration of particles is higher in one area than in another.
- cross-pollination - Cross-pollination is the transfer of pollen from the anther of one flower to the stigma of another flower on a different individual of the same…
d
- deamination - Deamination is the removal of an amino group from a molecule. Deaminase removes the amino group and the nitrogen waste is converted to ammonia and…
- deforestation - Deforestation, in simple terms, means the felling and clearing of forest cover or tree plantations to accommodate agricultural, industrial or urban use.
- detoxication - Detoxification or detoxication is the physiological or medicinal removal of toxic substances from a living organism, including the human body, which is mainly carried out…
- digestion - Digestion is the breakdown of large insoluble food compounds into small water-soluble components so that they can be absorbed into the blood plasma. In certain…
- diploid - A diploid cell has two complete sets of chromosomes. Most cells in humans are diploid, comprising 23 chromosome pairs, so 46 chromosomes in total. This…
e
- ecology - Ecology is the study of organisms and how they interact with the environment around them. An ecologist studies the relationship between living things and their…
- emulsification of fats - This is the process of breaking down the complex fat molecules converted into smaller fat molecules by the bile salts secreted by the liver that…
- endocrine glands - Endocrine glands are ductless glands of the endocrine system that secrete their products, hormones, directly into the blood. The major glands of the endocrine system…
- endolymph - Endolymph is a physiological fluid that fills the inner ear’s labyrinth and serves crucial sensory functions. Vibrational waves transmitted following the displacement of this fluid…
- extracellular - situated or occurring outside a cell or the cells of the body.
f
- fermentation - Fermentation is a natural process through which microorganisms like yeast and bacteria convert carbs — such as starch and sugar — into alcohol or acids,…
g
- gonad - The gonads, the primary reproductive organs, are the testes in the male and the ovaries in the female. These reproductive organs are essential for sexual…
- guttation - Guttation is the loss of water in the form of water droplets from hydathodes (small pores) on the tips or edges of leaves of some…
h
- haemoglobin - Haemoglobin (Hb) is a protein, found in the red blood cells, that carries oxygen in your body and gives blood its red colour.
- haploid - Haploid refers to the presence of a single set of chromosomes in an organism’s cells. Sexually reproducing organisms are diploid (having two sets of chromosomes,…
- hermaphrodite - A hermaphrodite is a sexually reproducing animal or flower that has both male and female reproductive organs. Hermaphroditic animals are mostly invertebrates such as worms,…
- heterotroph - A heterotroph is an organism that consumes other organisms in a food chain. The term stems from the Greek words hetero for “other” and trophe…
- homeostasis - Homeostasis is the process by which a living organism or system maintains a stable internal environment despite external changes. This balance is crucial for the…
- hormone - Hormones are chemical messengers produced by glands in the endocrine system that regulate various functions in the body by traveling through the bloodstream to target…
- hybrid vigour - Hybrid vigour, also known as heterosis or outbreeding enhancement, is the phenomenon that a hybrid offspring has improved traits, such as growth rate, biomass, stress…
- hypertonic solution - A hypertonic solution refers to a solution containing a higher solute concentration in comparison to the solute concentration in another solution, across a semipermeable membrane.
- hypotonic solution - Hypotonic solution refers to a solution containing a lower solute concentration in comparison to the solute concentration in another solution, across a semipermeable membrane. Such…
i
- implantation - Implantation is the embedding of the blastocyst into the endometrium of the uterus. Implantation begins about the 7th day after fertilisation of ovum and it…
- ingestion - Ingestion is the process of taking food into the body through the mouth into the gastrointestinal tract, such as through eating or drinking.
- insulin - Insulin is an essential hormone produced by the pancreas. It helps the body turn food into energy and manages blood sugar levels. The role of…
- integument - a tough outer protective layer, especially that of an animal or plant.
- intracellular - existing, occurring, located or functioning within a cell.
- isotonic solution - An isotonic solution is when two solutions, separated by a semipermeable membrane, have equal concentrations of solutes and water.
l
- lateral Meristem - Lateral Meristem is a type of meristematic tissue comprised of meristematic cells in the lateral areas of a plant and is associated with lateral growth.…
- legume - A legume is any plant that bears its fruit inside a pod. Legume is an umbrella term that includes beans and pulses. Thus, all beans…
- lignin - Lignin is an important organic polymer which is abundant in the cell walls of certain plants. It provides rigidity, holds a plant together and keeps…
m
- macronutrient - Macronutrients are nutrients that a plant needs in relatively large amounts. Essential macronutrients are nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), and…
- metabolic waste - Metabolic wastes are the substances leftover from metabolic processes (like cellular respiration) which are not absorbed by the organism and hence they should be excreted.…
- metabolism - Metabolism is the sum of the chemical reactions that take place within each cell of a living organism and that provide energy for vital processes…
- micronutrient - Micronutrients are nutrients that plants need in only small or trace amounts. Boron (B), chlorine (Cl), copper (Cu), iron (Fe), manganese (Mn), molybdenum (Mo), nickel…
- microorganism - Microbes are organisms that are too small to be seen without using a microscope. They include organisms like bacteria, archaea, and single-cell eukaryotes (organisms whose…
- morphology - Morphology is the study of the size, shape, and external structure of animals, plants, and microorganisms and their unique structural characteristics.
- motile - capable of motion.
- myelin - Myelin is an insulating layer, or sheath that forms around nerves, including those in the brain and spinal cord. It is made up of protein…
n
- NADH - NADH stands for “nicotinamide adenine dinucleotide (NAD) + hydrogen (H).” It is a chemical that occurs naturally in the body and plays a role in…
- neuron - Neurons are nerve cells that send messages all over your body to allow you to do everything from breathing to talking, eating, walking, and thinking.
- non-motile - not able to move by itself.
o
- osmoregulation - Osmoregulation is the process by which an organism regulates the water balance in its body to maintain homeostasis. In animals, this process is brought about…
p
- perilymph - Perilymph is an extracellular fluid located within the inner ear. It is found within the scala tympani and scala vestibuli of the cochlea.
- peristalsis - Peristalsis is produced by the involuntary contraction of circular muscles which is preceded by the simultaneous contraction of the longitudinal muscles and relaxation of the…
- permeability - Permeability is a measure of the ability of a porous material (having small spaces or holes through which liquid or air may pass) to allow…
- phloem - Phloem is a plant vascular tissue that conducts foods made in the leaves during photosynthesis, downwards to all other parts of the plant.
- photosynthesis - Photosynthesis is the process by which green plants, and some algae and bacteria, convert the energy of sunlight into chemical energy. This energy is then…
- phytoplankton - Phytoplankton and zooplankton are two types of plankton that are found in water. Phytoplankton are plants, while zooplankton are animals; this is the main difference…
- plankton - Plankton are microscopic organisms that live at and beneath the surface of lakes, rivers, ponds, and oceans across the planet. The word “plankton” comes from…
- precipitation - Precipitation is any liquid or frozen water that forms in the atmosphere and falls back to the Earth. It comes in many forms, like rain,…
- putrefaction - Putrefaction is the decay or rotting in the body or other organic matter by the action of microorganisms resulting in the production of a foul…
- putrefying bacteria - Putrefying bacteria are bacteria that are involved in the putrefaction of living matter. Putrefaction is the decay of organic matter by the action of microorganisms…
r
- regeneration - In Biology, regeneration is the natural process of replacing or restoring damaged or missing cells, tissues, organs, and even entire body parts to full function…
- root absorption - In higher plants, water and minerals are absorbed through root hairs which are in contact with soil water, and form a root hair zone a…
- root apical meristem - Root apical meristem, or root apex, is a small region at the tip of a root. It makes the root grow in length. It harbours…
s
- salinity - Salinity is the dissolved salt content of a body of water called saline water. It is the measure of the number of grams of salts…
- saprobe - An organism that lives off of dead or decaying organic material. They are free-living microbes. Examples are fungi. They act as decomposers in the food…
- Self-pollination - Self-pollination occurs when the pollen from the anther is deposited on the stigma of the same flower or another flower on the same plant.
- semi-permeable membrane - A semipermeable membrane is a layer that only certain molecules can pass through. Smaller molecules like water can pass but not the bigger molecules like…
- senescence - Senescence is the gradual deterioration of the functioning of cells. This process contributes to ageing and age-related diseases.
- synthesize - to produce a substance by combining other substances chemically.
t
- thallus - a plant body that is not differentiated into stem and leaves and lacks true roots and a vascular system. Thalli are typical of algae, fungi,…
- transpiration - Plants absorb a lot of water and transpiration is a means by which excess water is removed
- turbidity - Turbidity is a measure of the level of particles such as sediment, plankton, or organic by-products, in a body of water. As the turbidity of…
- turgid - Turgid describes something that’s swollen or congested, typically by fluids, for example, a turgid water balloon. In biology, turgid refers to cells or tissues that…
u
- urinogenital system - These, are the organs of the reproductive system and the urinary system. They are considered together because they share some common ducts. The urogenital system…
v
- vasoconstriction - Vasoconstriction is the narrowing (constriction) of blood vessels. It happens when smooth muscles in blood vessel walls tighten. When blood vessels constrict, blood flow is…
- vasodilation - Vasodilation refers to a widening of the blood vessels within the body. This occurs when the smooth muscles in the arteries and major veins relax.…
w
- worm cast - Worm cast is a structured mound of soil, mud and sand which is ejected on the surface after it has passed through the body of…
x
- xylem - Xylem is a plant vascular tissue that transports water and dissolved minerals from the roots to the stems and leaves and also provides physical support.…
z
- zooplankton - Phytoplankton and zooplankton are two types of plankton that are found in water. Phytoplankton are plants, while zooplankton are animals; this is the main difference…
- zygote - zygote is a fertilized egg cell that results from the union of a female gamete (egg, or ovum) with a male gamete (sperm).
We will keep updating this list with new terms, the same with our other categories. Feel free to contribute to this glossary using this comment section. 👨🏿🎓