Biology Dictionary
Click on the first letter of the word you are looking for.
Abiotic Factor
Any contribution to the environment that is of a non-living nature eg temperature, humidity, pH, soil type, moisture.
Absorption
The process by which small, soluble molecules enter the body. In animals the nutrient material from the gut is taken up by the blood system.
Activated Sludge
Sewage sludge which is rich in bacteria
Active Site
An area on the surface of an enzyme that has a shape complementary to a specific substrate, allowing the two to join. The idea is sometimes called the ‘lock and key’ mechanism.
ADH
See Anti-diuretic hormone
Aerobic Respiration
A type of respiration that goes on in cells and needs oxygen. The oxygen is used to completely oxidise foods such as glucose, releasing energy, water and carbon dioxide.
Agar
A jelly containing nutrients on which bacteria can be grown.
Air Sac
See alveolus
Alimentary Canal
The long muscular tube running from the mouth to the anus which makes up the digestive system.
Allele
A particular form of a gene and usually occur in pairs eg there is a gene which controls the height of pea plants. One form of the gene produces dwarf plants, the other produces tall plants.
Alveolus (air sac)
A small air filled sac wich are found in large numbers in the lungs of vertebrates and whose job is to increase the surface area for gaseous exchange.
Amino Acid
The bulding block of protein. Most can be made by the body, but others, called the ‘essential amino acids’ have to be taken in as part of a balanced diet.
Amniocentesis
A technique for the diagnosis of some congenital abnormalities before birth. In the technique amniotic fluid is removed using a syringe and the cells in the fluid are examined.
Amnion (amniotic sac)
A fluid filled bag surrounding the embryo as it develops, giving it space to grow and acting as a protective cushion.
Amniotic Fluid
The fluid surrounding the developing baby, acting as a shock absorber and protecting the baby from bumps and damage as the mother moves
Amniotic Sac
See amnion
Ampulla
Found in the semi-circular canals of the ear and concerned with balance.
Amylase
A digestive enzyme which splits up starch into smaller subunits called maltose. It works best in alkaline conditions and is found in saliva, the small intestine, seeds and tubers of plants.
Anaerobic Respiration
A type of respiration which goes on in cells and does not require oxygen. Foods such as glucose are turned into products such as lactic acid and ethanol and can only release a small amount of energy.
Annual Rhythm
Any behaviour which is repeated at yearly intervals eg bird migration, hibernation.
Antagonistic Pair
Two muscles which produce movement of a limb in opposite directions. Eg biceps and triceps muscles in the upper arm.
Anther
Part of the stamen of the flower where the male gametes are formed. Usually they have four pollen sacs in which the pollen grains develop.
Anti-Diuretic Hormone(ADH)
A hormone which can limit the water content of urine by controlling the reabsorption of water by the kidneys.
Antibiotic
Any substance produced by micro-organisms that kills or stops the growth of other micto-organisms eg penicillin is produced by a fungus called Penicillium notatum and works against many bacteria.
Anus
The exit from the alimentary canal.
Aorta
The main artery leading away from the heart.
Artery
A thick walled blood vessel taking blood away from the heart.
Asexual Reproduction
Reproduction that does not require the fusion of gametes. The offspring are therefore clones of the parents.
Atrium (plural –atria)
One of the upper chambers of the heart in mammals which receives blood from the body (right atrium) or the lungs (left atrium)
Auditory Canal
Air filled tube which directs sound waves to the eardrum.
Auditory Nerve
Carries nerve impulses from the cochlea to the brain.
Axon
Motor fibres which carry nerve impulses away from the central nervous system.
Azotobacter
A free-living soil bacteria which can absorb atmospheric nitrogen and convert it into nitrate.
Backcross
The identity of an unknown genotype can be found by ‘backcrossing’ it with a homozygous recessive partner. The resulting offspring will indicate what genotype the unknown parent is.
Bacteria
Single-celled organisms present in soil, water and air. They have various shapes occurring as cicci (spherical), bacilli (rod-shaped), and spirilla (coil-shaped)
Some are useful but many cause diseases.
Bacterial Spores
A reproductive cell or ball of cells surrounded by a thick resistant wall to withstand unfavourable conditions, such as drought. When conditions improve the spore germinates into a new individual.
Ball and Socket Joint
The type of joint found in the shoulder and hip of mammals. The shapes of the bones of the joint are like an interlocking ball and socket, giving the joint movement in three planes.
Batch Processing
Any industrial process which converts a starting material to a product by a series of steps which are repeated for each load of starting material.
Benedict’s Solution
A blue solution which turns a brick-red colour when heated with simple reducing sugars.
Biceps
The muscle found in the front of the upper arm.
Bile
Helps convert large drops of fat into tiny droplets, thereby increasing the surface area upon which lipase can act.
Bile Duct
Small tube which carries bile from the liver to the duodenum.
Binocular Vision
A type of vision where the image of an object falls on the retina of both eyes simultaneously. This results in stereoscopic or 3-D vision.
Biological Clock
Any behaviour which is repeated at regular intervals and controlled internally by a biological clock.
Biological Detergent
Detergents which contain enzymes produced by bacteria.
Biomass
The total mass of organisms in a given environment. It is measured as either live or dry weight per unit area.
Biosphere
The part of the Earth’s surface and its immediate atmosphere which is occupied with living organisms.
Biotechnology
The use of organisms or their enzymes for the manufacture of useful substances.
Biotic Factor
The influences which occur within an environment as a result of the activity of living organisms. eg competition for food or mates, predation, disease.
Bladder
The site of temporary storage of urine.
Blind Spot
The point in the eye where receptors are absent and fibres from the retina enter the optic nerve.
Bronchiole
One of the smaller tubes branching off from the bronchii in the lungs of mammals.
Bronchus (plural – bronchii)
One of a pair of tubes linking the trachea with the lungs, in mammals.
Canine Tooth
One of four pointed teeth present in the jaw between the incisors and premolars in mammals. It is used for stabbing and holding food, especially flesh.
Carbohydrate
A family of molecules containing the elements carbon, hydrogen and oxygen.
Carbohydrates provide the body with an energy supply.
Examples are glucose and starch.
Capillary
One of the many tiny blood vessels joining small arteries (arteioles) to small veins(venules). The capillary walls are a single layer thick and this lets molecules diffuse across easily.
Carnivore
Any animal that eats flesh.
Carpel
The female part of the flower.
Cartilage
A soft bone-like material which covers the ends of bones to act as a protective cushion and shock absorber. It is also found in the trachea where it prevents the trachea from kinking.
Catalase
An enzyme found in the liver and potato tubers whose function it is to catalyse the breakdown of toxic hydrogen peroxide into water and oxygen.
Catalyst
A chemical which speeds up a chemical reaction. Those produced by living cells are called enzymes.
Cell Division
The division of a cell inot two new cells called daughter cells, during growth and reproduction.
Cell Membrane
The outer boundary of a cell which gives some shape and acts to control molecules entering or leaving the cell.
Cellulose
A carbohydrate which is used to make the cell wall of plant cells. It is made up of long branches of glucose molecules.
Cell Wall
A thick rigid coat of cellulose formed outside the cell membrane – found only in plant cells.
Cerebellum
The part of the brain which is responsible for balance and muscular
co-ordination.
Cerebrum
In mammals, the enlarged lobes of the fore-brain which are associated with the senses, muscular movement, thought and memory.
Chemical Reaction
An action that takes place between chemicals in which some other substance or substances are formed.
Chlorophyll
The coloured pigment found in most green plants. Its function is to trap light energy from the sun for photosynthesis.
Chloroplast
An organelle found in the cells of green plants which contain the chlorophyull necessary for photosynthesis.
Choice Chamber
A piece of apparatus which allows one variable to be studied at a time.
Chromatid
When a chromosome becomes shorter and thicker during the first satge of mitosis it is seen to become a double thread. Each thread is a chromatid.
Chromosome
A coiled structure found in the nucleus which carries the genetic material making up the genes. Each species of organism has a typical number eg 46 in humans, 20 in maize.
Chromosome Number
The number of chromosomes found in a diploid cell. Usually the chromosomes are in identifiable pairs and the number is characteristic of the organism. eg 46 in humans, 10 in maize.
Cilia
Microscopic hair-like structures on the cells lining the trachea, bronchii and bronchioles. They beat and move mucus up towards the mouth.
Circadian Rhythm
Any behaviour that is repeated regularly every 24 hours. Eg Cockroaches show a peak of activity at night.
Clone
A group of cells all originating from the same, single parent cell and as a result are identical to each other.
Cochlea
A coiled tube in the inner ear which is concerned with the pitch of sound received at the ear.
Community
A naturally occurring group of different organisms living together in the same ecosystem.
Companion Cell
A cell which acts as a companion to the sieve tube. As sieve tubes lose their nucleus when they mature these cells may act to control them.
Cone Cell
Cells in the retina of the eye which is sensitive to bright light and colour.
Conservation
The preservation, protection and management of an environment which allows for agriculture, recreation, the removal of natural resources and aesthetic needs while caring for the plants and animals.
Consumer
An organism which consumes other organisms for food.
Continuous Flow Process
An industrial process that continuously converts the starting material to the final product without having to stop or start, the starting material being added and the final product being removed continuously.
Continuous Variation
A feature of some characteristics, eg height in which there is a complete range of forms. The characteristic often produces a normal distribution curve when a large population is sampled.
Control
An experiment carried out to provide a standard of comparison for other experiments. eg where a fertiliser is being tested on a plant, the control would be the same experiment without fertiliser.
Coordination
The ability to carry out a number of actions at the same time, especially using several muscles together.
Cornea
A transparent layer at the front of the eye covering the iris.
Coronary Artery
The artery which supplies oxygen and food to the muscle cells of the heart itself.
Cotyledon
A part of a plant embryo in the form of a specialised seed leaf that acts as a storage organ and as a first leaf after germination. Monocotyledons have 1 leaf. Dicotyledons have 2 leaves.
Cuticle
A thin non-cellular layer secreted by the epidermis. It covers all the outside of the leaf except where there are stomata. It helps to reduce water loss.
Cuttings
A method of artificial propagation in plants whereby a piece of stem is cut from the parent plant and allowed to develop its own root system and so producing a new plant in the process.
Cytoplasm
The fluid part of the cell. It is the site of cellular chemical reactions and contains many enzymes.
Decay
A natural process whereby certain micro-organisms (decomposers) obtain energy and building materials from organic waste.
Decomposers
Often micro-organisms which break down waste materials and dead organisms.
Degradation
The process of breaking down a large molecule into smaller molecules.
Denatured
Altered permanently, with the result that there are changes in the way the substance behaves. eg A denatured enzyme loses its enzyme activity.
Denitrification
The process where nitrates in the soil are converted into nitrogen gas in the air.
Destarching
The removal of starch. Usually this is carried out with plants, prior to their being used to show the production of starch by photosynthesis.
Dialysis
Where blood is purified by a machine if the kidneys are not working.
Diaphragm
A dome-shaped muscular sheet stretched across the lowest ribs, which allows inspiration and expiration.
Diffusion
The movement of molecules of one kind from an area of high concentration to an area of low concentration until they reach equilibrium (ie are evenly spread)
Digestion
A process requiring enzymes in which the complex, insoluble molecules of food are broken down into simpler, soluble molecules which can be absorbed by the body.
Discontinuous Variation
A variation in which different forms of a characteristic fall clearly into separate groups. eg blood group, gender, ability to roll the tongue.
Distribution
The occurrence of an animal or plant over the total area in which it covers.
Diurnal Rhythm
Any behaviour or process which shows most activity during daytime and least at night.
(opposite to ‘nocturnal’)
Dominant
An allele which can mask another allele for the same gene. Usually the symbol is written as a capital letter. eg black coat colour in gerbils (B) is dominant to white coat colour(b)
Down’s Syndrome
A human abnormality caused by an extra chromosome in each cell. The main signs of the syndrome are mental retardation, heart defects. And very rounded features.
Drosophila
See Fruit fly
Ear Drum
A membrane between the outer and middle ear which vibrates when hit by sound waves. This vibration is transmitted by the ear bones to the oval window.
Ecosystem
A natural biological unit made up of living and non-living parts.
Effector
Any part of the body which responds to an impulse given by a nerve.
Embryo (in animals)
The stage of development between the time that the fertilised egg begins to divide and the developing animal hatches or is born.
Embryo (in plants)
The part of a seed which develops into the root (radicle) and shoot (plumule) of a plant.
Endospore
A resistant spore that bacteria become to protect themselves from, for example, extremes of temperature, drying out, disinfectants, etc.
Environment
The surroundings of any organism which includes biotic and abiotic factors such as influences of climate or other plants or animals.
Enzyme
A catalyst produced by living cells to speed up chemical reactions, eg
Pepsin, catalase.
Enzymes are made of protein.
Epidermis
A thin tissue, usually one cell thick that surrounds young roots, stems and leaves.
Epithelium
A cellular lining, usually only one cell thick found for example on the villi of the small intestine.
Eustachian Tube
The tube leading from the middle ear to the back of the throat.
Excretion
The extraction and elimination from the body of the waste products of metabolism.
Expiration
Air exhaled by the action of the diaphragm and intercostal muscles and the downward movement of the rib cage.
Extensor
Following the extension of the arm for example, the biceps (the flexor muscle) contracts to pull the relaxed triceps(the extensor muscle).
F1 Generation
The first generation of a particular cross(mating). The number is changed to indicate the generation. Thus the F3 would be the great grandchildren of a particular pair of individuals.
Faeces
The unwanted part of food once it has passed through the alimentary canal after digestion.
Fat
A group of organic molecules containing the elements carbon, hydrogen and oxygen, made up from glycerol and fatty acids. Fat is a food store, protective layer for organs and heat insulator.
Fatigue
The muscle can no longer contract due to the build up of lactic acid caused by the lack of oxygen.
Fatty Acids
One of the two products of the digestion of fat – the other being glycerol. Fatty acids can be saturated (ie containing no C=C double bonds) or unsaturated.
Femur
The long thigh bone.
Fermentation
A type of respiration found in some plants and unicellular organisms which does not require oxygen, resulting in the production of ethanol (alcohol) from glucose.
Fertilisation
The process in which the male and the female gametes (sex cells) fuse together to form a single cell called a zygote.
Filament
The male part of a flower which carries the anther at the top of it.
Flower
The part of the plant responsible for sexual reproduction.
Foetus
The developing embryo is known as a foetus once it can be recognised as a species.
Food Chain
A sequence of organisms organised in such a way that the second group (herbivores) feed on the first group (primary producers) and so on. Eg
Producer ------à Herbivore-----à Carnivore
Food Web
A number of food chains linked together by having the same animals or plants in parts of the different food chains.
Fovea
The small depression in the retina of the eye containing cone cells only. This is the point of most accurate vision.
Fruit
A plant structure consisting of one or more ripening ovaries, with or without seeds. Many fruits are succulent, such as berries, but others contain no fleshy tissue, eg peas.
Fruit Fly (Drosophilia)
A tiny insect commonly used in genetics experiments.
Gall Bladder
A small organ attached to the liver which stores bile.
Gametes
The sex cells which fuse together at fertilisation to form the zygote. In animals the gametes are the sperm in males and the ovum(egg) in females. In plants the gametes are the pollen in the male and the ovules in the female.
Gene
A unit of heredity passed on from one generation to another. All of the vast number of these units are held by the chromosomes and provide our characteristics.
Genetics
The study of genes and the acquisition of characteristics from the parent(s) of the organism.
Genetic Engineering
The changing of the genetic material in an organism to improve it. This could be by selective breeding, but also covers the artificial transfer of genetic material from one organism to another.
Genotype
The genetic make-up of an individual usually referring to specific characteristics. eg The two alleles for the human albino gene can be written as A and a, giving AA, Aa and aa as the three possible genotypes.
Germination
The beginning of the growth of a seed, spore or other structure that has been dormant.
Gestation
The period of development of a foetus inside the mother.
Glomerular Filtrate
Plasma fluid containing glucose, salts, urea and water which filter through the walls of the glomerulus into the Bowman’s capsule.
Glomerulus
A tiny knot of blood capillaries surrounded by the Bowman’s capsule in the kidney.
Glucose
A type of simple sugar. It is an important source of energy.
Glycerol
One of the two products of fat digestion – the other being fatty acids.
Grafting
A method of artificial propagation where a cutting from a cultivated variety of fruit tree or bush is grafted on to the stock of a hardy variety.
Guard Cell
One of a pair of specialised cells in the epidermis which controls the size of the stoma at the leaf surface.
Gullet
Also known as the oesophagus. It is the tube leading from the mouth to the stomach.
Habitat
The part of the environment which is occupied by an animal or plant, for example, stream, meadow, salt marsh, etc.
Haemoglobin
A red-coloured, iron containing protein found in red blood cells which can bind with molecules of oxygen to form oxy-haemoglobin.
Herbivore
Any animal that eats plant material.
Heterozygote
An organism containing two different alleles for a gene. For example if a gene has alleles A and a, then the heterozygous type is Aa.
Hinge Joint
A type of joint found in the elbow, knee and fingers of mammals. The bones are shaped so they can move in only one plane – like a hinged door.
Homozygote
An organism containing two identical alleles for a gene. Thus if a gene has two alleles, A and a, then two homozygote types are possible – AA and aa.
Humerus
The upper arm bone
Humus
Dark brown organic material formed during the decomposition of plant and animal remains.
Hydrogen Peroxide
A toxic substance which builds up in cells as a result of chemical reactions. It is broken down to water and oxygen by the action of the enzyme catalase.
Immobilisation
A technique used in biotechnology to make soluble enzymes more easy to handle by attaching them to a large object. The enzyme can be trapped in jelly-like beads or chemically linked to plastic.
Immobilised Enzyme
An enzyme which cannot move freely in its substrate because it has been deliberately attached to another substance eg gel pellets.
Implantation
When an embryo passes from the oviduct to the uterus it becomes attached to the uterine wall.
Incisor
A front chisel-shaped tooth in mammals used for cutting and gnawing.
Indicator Species
A species that only thrives under certain environmental conditions and whose presence shows that these conditions are present.
Inheritance
The acquisition of characteristics by the transfer of genetic material from ancestor to descendant.
Inhibition
A state in which an enzyme is unable to act as a catalyst.
Inspiration
Air is inhaled due to contraction of the intercostal muscles and the diaphragm.
Insulin
A hormone which controls the amount of sugar in the blood. Under production of insulin by the body causes diabetes – a condition which can be fatal if left untreated.
Intercostal Muscles
The muscles attached between the ribs to help in inspiration and expiration.
Intestine (large)
The long tube in the alimentary canal responsible for absorbing water from the faeces.
Intestine (small)
The long coiled tube in the alimentary canal responsible for digestion of some food types and the absorption of the products of digestion.
Iodine Solution
An orange/brown liquid chemical used for staining cells so they can be seen more clearly under the microscope.
It is also used to test for the presence of starch. It will go blue/black if starch is present.
Iris
The coloured part of the eye. It surrounds the central hole (the pupil) and can change the size of the pupil and so alter the amount of light entering the eye.
Joint
The meeting point between two bones. There are two main types of joint – hinge and ball and socket.
Kidney
The organ which regulates water content of the body and removes urea from the blood.
Kwashiorkor
The most common and widespread human nutritional disease caused by the acute lack of protein in the diet.
Lacteal
Found in the villi of the small intestine. It collects the products of fat digestion – fatty acids and glycerol – for distribution around the body.
Lactic Acid
The chemical produced during anaerobic respiration in muscle cells which causes muscle fatigue.
Lacto-bacillus
A rod –shaped bacterium which is used to sour milk in the production of yogurt and cheese. The enzymes of the bacteria convert lactose into lactic acid.
Lactose
A sugar found in milk. The souring of milk is due to the conversion of lactose into lactic acid by micro-organisms in the air.
Large Intestine.
See "intestine"
Larynx
The top part of the passage (trachea) leading from the throat to the lungs. It contains the vocal cords.
Layering
A method of artificial propagation where a healthy side-branch is fixed into the soil to allow roots to form. This method is commonly used to culture carnation plants.
Leguminous Plant
A plant which has root nodules containing the nitrogen-fixing Rhizobium bacteria. Examples are peas, beans, clover and lupins.
Lens
A transparent structure inside the front part of the eye which focuses the light entering the eye onto the back of the eye (retina).
Ligament
A band of elastic connective tissue that joins bone to bone. It is especially suited to withstand sudden stresses upon a joint.
Lignin
A polymer found in plant cell walls which provides stiffening (eg xylem vessels and bark fibres). Lignified tissue is made of dead cells.
Limiting Factor
A factor which holds up a process because it is in short supply. Eg temperature in photosynthesis.
Lipase
A digestive enzyme produced by the pancreas which acts on fats and oils in the small intestine. It breaks fats and oils into fatty acids and glycerol.
Lung
The organs responsible for gaseous exchange.
Lymphatic Vessel
See "Lacteal"
Malting
A process used in the brewing industry involving the germination of grain seed. The germination starts the conversion of starch, stored in the seed, into sugars which can be removed and fermented.
Maltose
A type of sugar made of two glucose units. It is produced when starch is broken down by the action of the enzyme amylase.
Medulla (oblongata)
The back of the hind-brain that connects with the spinal cord in vertebrates. It is associated with automatic nervous control m(ie not controlled by will-power) eg heartbeat, breathing.
Malnutrition
Bad nutrition. This can be caused by the lack of food, an unbalanced diet or even eating more food than is required by the body.
Mendel (Gregor)
An Austrian monk and mathematician who working with strains of garden peas managed to work out the basic facts about how genes are transmitted between generations. Lived between 1822-84.
Mesophylls
The internal tissues of a plant leaf, not including the veins. There are two types: upper palisade mesophyll and a loosely packed spongy mesophyll.
Metabolism
The total of all the chemical reactions occurring in the cells, both the building up of molecules and the breaking down of molecules.
Micro-organisms
Any uni-cellular (single-cells) organism such as protozoan, bacterium, virus or fungus.
Microtome
An instrument used for cutting very thin sections for microscopic examination.
Mitosis
A type of cell division by which two daughter cells are produced from one parent cell, with no change in the number of chromosomes. It is the basis of asexual growth and repair.
Molar
A tooth at the back of the jaw in a mammal used for crushing food. It is not preceded by a milk-tooth.
Monohybrid
An organism that carries two alleles of one gene. For example a characteristic controlled by alleles A and a, would produce a monohybrid genotype of Aa. Ie a heterozygote.
Monohybrid Cross
A breeding programme in which two parents are crossed (mated) to produce mono-hybrids, which are then mated.
Mucus
A sticky material produced by cells in the lining of the windpipe which traps dirt particles. This is then removed by the beating cilia.
Multi-disc
A star-shaped piece of sterile filter paper. Each arm of the paper contains a different anti-biotic. It is used to identify which anti-biotic is effective against particular bacterial diseases.
Mutagenic Agent
Anything that can cause mutations. eg X-rays, UV light, mustard gas.
Mutant
Any organism that is suffering from a mutation.
Mutation
A change in the genetic material of an organism. They can be spontaneous or they can be induced by chemicals or radiation.
Nectar
A sugary solution produced by insect pollinated flowers to attract insects.
Nectary
An area of tissue in a flower which secretes sugary nectar to attract insects and bring about pollination.
Nephron
A filtering unit in the kidney.
Nerve
Cells capable of carrying information from the body’s sense organs to the central nervous system and vice versa.
Neurone
Consists of a cell body attached to fibres.
Nitrate
The form of nitrogen which plants can take up and use in the soil.
Nitrification
A process brought about by bacteria which converts ammonium compounds to nitrite and nitrite to nitrate.
Nitrobacter
A soil-living bacteria which converts nitrites to nitrates.
Nitrosomonas
A soil-living bacteria which converts ammonium compounds to nitrates.
Nodule
Found on the roots of leguminous plants (eg clover, beans, lupins, peas) and contain Rhizobium bacteria which are capable of fixing nitrogen and converting it into nitrates.
Nucleus
Part of the cell which controls its activities including cell division.
Omnivore
An animal which eats both plant and animal material. eg humans
Optic Nerve
The nerve which takes nerve impulses from the eyes to the brain.
Optimum
For an enzyme, the best conditions for enzyme activity. eg optimum pH or optimum temperature.
Organism
Any living plant or animal.
Osmosis
A special name given for the diffusion of water molecules. The water molecules move from a high concentration to a low concentration over a semi-permeable membrane.
Ossicles
In mammals, the three bones of the middle ear (hammer, anvil and stirrup) which connect the ear drum to the oval window.
Ovary (animal)
The organ which produces the female gametes (sex cells).
Ovary (plant)
The female part of the flower that contains one or more ovules (egg cells).
Oviduct
A tube that carries the ovum (egg) to the outside, or in the case of mammals to the uterus where it becomes implanted if fertilisation has occurred.
Ovule
The part of the ovary in a plant which contains the egg cell and develops into a seed after fertilisation.
Ovum (egg)
The egg cell or female gamete. In humans it is about 0.14mm in diameter and about 50,000 times larger than the human sperm.
Oxy-haemoglobin
In the presence of a high concentration of oxygen, haemoglobin readily combines with it to form oxy-haemoglobin.
Palisade Mesophyll
Rectangular shaped cells found under the upper epidermis of the leaf which contain many chloroplasts.
Pancreas
A leaf-shaped organ situated just below the stomach which produces the digestive enzymes lipase, amylase and trypsin and the hormone insulin.
Penis
The organ of the male mammal which moves sperm into the reproductive system of the female during copulation.
Pepsin
An enzyme produced by the cells of the lining of the stomach which breaks down proteins into short polypeptide chains. Pepsin works best in acid conditions.
Peristalsis
A wave of muscular contraction and relaxation which passes along animal intestines moving food in one direction.
pH
A measure of acidity (the hydrogen ion concentration)
pH Meter
An instrument used to measure the acidity or alkalinity of a sample.
Phenotype
The observable features of an individual resulting from the genotype. Sometimes two genotypes will produce the same phenotype if the dominant allele masks the recessive allele.
Phloem Tubes
Part of the vascular bundle which has the job of transporting dissolved organic material (eg glucose) by translocation. The tissue is made up of seive tubes and companion cells.
Phosphorylase
The enzyme found in potatoes which speeds up the reaction to convert glucose into starch.
Photosynthesis
The process whereby plants trap light energy by the pigment chlorophyll and convert it into chemical energy.
Light + Carbon dioxide + Water ----à Glucose + Oxygen
Pitfall Trap
A trap (eg a jar sunk into the ground) into which small mobile animals may fall and from which they are unable to escape.
Pituitary Gland
The gland attached to the brain which amongst other things produces ADH.
Placenta
The structure formed from the tissues of the embryo and mother at the point of attachment of the embryo to the mother, through which the embryo is nourished.
Plasma
A straw coloured liquid in which the blood cells are suspended. It is 90% water and contains soluble proteins, dissolved gases, sugars, waste products and salts.
Plasmolysis
When plant cells are placed in a lower water concentration than the cell contents the living contents of the cell shrink and pull away from the cell walls due to the process of osmosis.
Pleural Membrane
The thin sheet covering the entire surface of the lung.
Pleurococcus
A single celled plant with a powdery green appearance which is commonly found growing on tree trunks.
Pollen Tube
A slender structure produced from the pollen grain after pollination. It grows down through the stigma, style and ovary allowing the gamete of the pollen grain to move to the gamete in the ovule.
Pollen
The male sex cell (gamete) produced by the anther in plants.
Pollination
The transfer of pollen from the male to female reproductive organs in plants. It can be carried by insects or by the wind.
Pooter
A piece of equipment for collecting insects. It is basically a bottle into which the insects are sucked up.
Population
The total number of plants or animals of one species living in a particular place.
Predator
An animal that lives by hunting and eating other animals.
Premolar
A cheek tooth in mammals, situated between the canine and molars used for grinding food.
Prey
Any animal that is hunted for by another animal.
Producer
An organism (usually a plant) which can make organic material (eg glucose) and thus forms the basis of a food chain.
Product
A chemical produced as a result of a chemical reaction.
Propagation
Any method of cultivating plants.
Protease
Any enzyme which splits up protein into polypeptides or amino acids. The enzymes usually works best in acid conditions. eg pepsin.
Protein
A complex molecule built up from amino acids joined together by peptide bonds. All proteins contain the chemical elements carbon, hydrogen, oxygen and nitrogen. Some also contain sulphur and phosphorous.
Pulmonary
-artery The blood vessel going from the heart to the lungs.
-vein The blood vessel going from the lungs to the heart.
Pupil
The opening surrounded by the iris. It controls the amount of light entering the eye.
Pure-breeding
See "true-breeding"
Pyramid of Biomass
A method of depicting the trophic levels to show the total mass of organisms at any one level.
Pyramid of Numbers
A method of depicting the trophic levels to show the number of organisms at any one level. A broad base shows the large number of producers. The next, narrower level shows a smaller number of consumers.
Quadrat
A piece of equipment, often 1 metre squared used for sampling an area in population studies.
Random Sampling
Sampling without making a decision about where to take the sample from.
Recessive
An allele that only shows its effect in the phenotype when present in a homozygous pair (eg aa). When paired with a dominant allele the effect of the recessive allele is hidden. (eg Aa)
Reflex arc
The nervous connections between receptor and effector that produces a simple response from a simple stimulus – called a "reflex action" eg knee jerk.
Respiration
The process occurring in a cell when the energy in food is being released. There are two types of respiration – aerobic (using oxygen) and anaerobic (not using oxygen)
Retina
A lining on the inside of the eye which is sensitive to light. The layer is made up of cells (rods and cones in humans) which are connected to the optic nerve.
Runner
A long, slender stem running along the surface of the ground to allow rapid vegetative propagation by a plant over its surrounding area.
Seed coat (testa)
A protective coat around the seed.
Seed Dispersal
The movement of seeds away from the parent plant so that they can germinate and grow into mature plants. The seeds can be moved by wind, water, animals or even explosive mechanisms.
Selective Breeding
The breeding of animals and plants to improve their desired characteristics. eg fungus resistance in cereals, more wool on sheep.
Selectively Permeable
See "semi-permeable"
Semi-circular Canals
Three fluid filled tubes, used for balance found in the inner ear. The canals are in each plane – two vertical at right angles to each other, one horizontal and at right angles to the other two.
Semi-permeable
The ability of a membrane to allow small molecules to pas through (eg glucose, oxygen, carbon dioxide) but not large molecules(eg starch, protein).
Sex Determination
The control of maleness or femaleness by genes located on the sex chromosomes. For humans the male sex is determined by the presence of the Y chromosome and the female by two X chromosomes.
Sieve Plate
The boundary between two sieve tubes of the phloem. It has small perforations, and these holes allow the cytoplasm to be continuous from cell to cell.
Species
A group of animals or plants which have similar characteristics and can form a breeding population to produce fertile offspring.
Specific
In enzymes, the ability to link with only one type of substrate. eg Amylase will only use starch as its substrate and catalase will only use hydrogen peroxide.
Sperm
The male gamete produced by animals which is microscopic in size and can move using its "tail"
Stamen
The male organ of a flower consisting of a stalk (filament) bearing an anther in which pollen grains are produced.
Stigma
The upper part of the female organ of a flower. The surface produces a sugary solution which helps the germination of pollen grains.
Stoma (plural: stomata)
An opening in the epidermis of leaves that allows gaseous exchange. The size of the opening is controlled by two guard cells.
Style
The female part of the flower connecting the stigma to the ovary.
Substrate
A substance upon which the enzyme acts.
Synovial Joint
A moveable joint which has a bag of viscous fluid (synovial fluid) acting as a lubricant between the bones of a joint.
Synthesis
The process of building up a large molecule from two or more smaller molecules.
Tendon
A band of non-elastic connective tissue which joins muscle to bone.
Testis
The organ which produces the male gametes, called sperm.
Tissue
Any large group of cells of similar structure in animals or plants which carry out a specific job. eg muscle, phloem, etc.
Trachea
A tube lined with rings of cartilage which connects the mouth and nose with the lungs. Also called the windpipe.
Transect
A line across a habitat along which the organisms are sampled to study changes that may occur along the line, eg for changes in vegetation between wet and dry areas of moorland.
Trophic Level
Any of the feeding levels that energy passes through as it moves through the ecosystem, eg producers, primary and secondary consumers.
True (pure) breeding
Characteristic of a strain of organisms that are all homozygous for the genes being studied, so that their offspring show no variation from the parent.
Umbilical cord
The cord which connects the developing embryo to the placenta. It is made up of blood vessels and connective tissue and is cut through at birth.
Upgrading of Waste
A process which takes waste of little value (eg sewage) and converts it into another, more valuable substance (eg biogas).
Urease
An enzyme which speeds up the breakdown of urea into ammonia and carbon dioxide.
Ureter
A tube which carries urine from the kidney to the bladder.
Urethra
A tube which leads from the bladder to the outside environment.
Urine
A solution containing water, urea and salts, produced by the kidney to be excreted from the body.
Uterus (womb)
Part of the female reproductive system in which the embryo implants and develops before birth.
Vacuole
A space within the cytoplasm of a plant cell containing a watery solution of salts and sugars.
Vagina
Part of the female reproductive system of mammals into which the penis is inserted during copulation.
Valve
A piece of tissue that allows movement of a liquid (eg blood) in only one direction. They are found in the veins and between the chambers of the heart.
Variation
Any differences (both in genotype or in phenotype) between individuals of a population, or between parents and their offspring.
See also "Continuous Variation" and "Discontinuous Variation"
Vein
A thin walled blood vessel with valves that takes blood back to the heart.
Ventricle
One of the two lower chambers of the heart in mammals which pump blood to the lungs (right ventricle) or to the body (left ventricle).
Villus (plural:villi)
A finger-like outgrowth in the lining of the small intestine which increases the surface area of the gut wall and contains blood vessels and lacteals to absorb the products of digestion.
Vitamins
Organic molecules which are necessary in the diet for normal growth and health. eg the lack of vitamin A causes night-blindness, the lack of vitamin C causes scurvy.
X-Chromosome
A type of sex chromosome shaped like an X, which is present in pairs (XX) in cells from a female and present with a Y chromosome (XY) in cells of the male.
Xylem Vessels
Empty tubes formed by cells joining together, end to end. The cells have strong walls which are re-enforced with rings of lignin. Their main job is to transport water for transpiration.
Y-Chromosome
The smaller of the two sex-chromosomes and shaped like a Y. It is found in the cells of male mammals together with one X chromosome.
Yeast
A name used to describe a number of different fungi which are important in the brewing and bread making industries. They produce enzymes which convert sugar into alcohol and carbon dioxide.
Yolk
The food store in the eggs of most animals, being made mostly of protein and fat.
Zygote
The name given to a fertilised egg.
The developing embryo is known as a foetus once it can be recognised as a species.