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. More
- 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). The small intestine absorbs most of... More
- 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 form of ATP. More
- 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 benefits to the aerobic organism, as... More
- afforestation - Afforestation is the establishment of a forest or stand of trees (forestation) in an area where there was no recent tree cover. More
- 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 fluid it contains are sometimes referred... More
- 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 cells that makes them red) are... More
- 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 oxygen is present. Anaerobic means living,... More
- 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 an area of the brain called... More
- 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 position along the shoot. The shoot... More
- 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 any biological system. More
- 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 releases it to fuel other cellular... More
- 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 of any other organisms. The word... More
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, fish and the cell walls of... More
- 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 nourishment and protection for the developing... More
- concentration gradient - A concentration gradient occurs in a solution or gas when the concentration of particles is higher in one area than in another. More
- 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 species. More
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 then removed from the body through... More
- deforestation - Deforestation, in simple terms, means the felling and clearing of forest cover or tree plantations to accommodate agricultural, industrial or urban use. More
- 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 by the liver. The liver is... More
- 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 organisms, these smaller substances are absorbed... More
- 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 is 22 pairs of autosomes and... More
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 habitats. More
- 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 will be easier to digest with... More
- 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 include the pineal gland, pituitary gland,... More
- 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 from outside stimuli convey information about... More
- extracellular - situated or occurring outside a cell or the cells of the body. More
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, anaerobically releasing energy. More
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 reproduction since they are responsible for... More
- 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 vascular plants. Below is an explanation... More
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. More
- 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, one from each parent). In humans,... More
- 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, trematodes (flukes), snails, moss animals, slugs... More
- 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 for “nourishment.” More
- 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 proper functioning of biological systems. Homeostasis... More
- 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 organs and tissues. They play crucial... More
- 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 tolerance, and fertility. For example, hybrids... More
- 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. More
- 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 a solution has a decreased solute... More
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 takes about 3 days for the... More
- ingestion - Ingestion is the process of taking food into the body through the mouth into the gastrointestinal tract, such as through eating or drinking. More
- 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 insulin in the body is to... More
- integument - a tough outer protective layer, especially that of an animal or plant. More
- intracellular - existing, occurring, located or functioning within a cell. More
- isotonic solution - An isotonic solution is when two solutions, separated by a semipermeable membrane, have equal concentrations of solutes and water. More
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. Meristems help in increasing the thickness... More
- 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 are considered a legumes, but not... More
- 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 the structure of the plant stable.... More
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 sulfur (S). More
- 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. Metabolic wastes can be categorized into... More
- 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 and for synthesizing new organic material.... More
- 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 (Ni), and zinc (Zn) areconsidered micronutrients.... More
- 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 cells have a nucleus e.g. amoeba... More
- morphology - Morphology is the study of the size, shape, and external structure of animals, plants, and microorganisms and their unique structural characteristics. More
- motile - capable of motion. More
- 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 and fatty substances. This myelin sheath... More
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 generating energy. In people, NADH supplements... More
- 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. More
- non-motile - not able to move by itself. More
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 by osmoreceptors, which can detect changes... More
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. More
- 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 circular muscles that push the bolus... More
- 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 fluids to pass through it. More
- phloem - Phloem is a plant vascular tissue that conducts foods made in the leaves during photosynthesis, downwards to all other parts of the plant. More
- 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 used to synthesize carbohydrates such as... More
- 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 between them. Larval crustaceans and krills... More
- 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 the Greek for “drifter” or “wanderer.”... More
- 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, sleet, and snow. More
- 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 smell. It occurs between 10 to... More
- 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 resulting in the production of a... More
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 in plants and animals. More
- 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 little behind the root tips. Diagrammatic... More
- 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 stem cells that are capable of... More
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 per kilogram of seawater, which is... More
- 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 chain. More
- 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. More
- 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 solutes. It allows cells to keep... More
- senescence - Senescence is the gradual deterioration of the functioning of cells. This process contributes to ageing and age-related diseases. More
- synthesize - to produce a substance by combining other substances chemically. More
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, lichens, and some liverworts. More
- transpiration - Plants absorb a lot of water and transpiration is a means by which excess water is removed More
- 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 water increases, it becomes denser and... More
- turgid - Turgid describes something that's swollen or congested, typically by fluids, for example, a turgid water balloon. A balloon filled with water is turgid. In biology, turgid refers to cells or tissues... More
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 is in charge of urine production,... More
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 slowed or blocked. Vasoconstriction may be... More
- 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. Vasodilation occurs naturally in response to... More
w
x
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 between them. Larval crustaceans and krills... More
- zygote - zygote is a fertilized egg cell that results from the union of a female gamete (egg, or ovum) with a male gamete (sperm). More
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. 👨🏿🎓