IGCSE Biology

For the Teachers' Day CAS

Species

a group of organisms that can reproduce to produce fertile offspring

Cell membrane

a very thin layer surrounding the cytoplasm of every cell; it controls what enters and leaves the cell

Diffusion

the random net movement of particles from a region of their higher concentration to a region of their lower concentration down a concentration gradient

Emulsion

a liquid containing two substances that do not fully mix; one of them forms tiny droplets dispersed throughout the other

Enzyme

a protein that increases the rate of a chemical reaction and is not changed by the reaction; Biological catalyst

Guard cells

a pair of cells that surround a stoma and controls its opening; guard cells are the only cells in the epidermis that contain chloroplasts

Peristalsis

rhythmical muscular contractions that move food through the alimentary canal

Translocation

the movement of sucrose and amino acids in the phloem from sources to sinks

Artery

a thick-walled blood vessel with a relatively narrow lumen that takes high-pressure blood away from the heart

Active immunity

long-term defence against a pathogen by antibody production in the body

Oxygen debt

extra oxygen that is needed after anaerobic respiration has taken place, in order to break down the lactic acid produced

Hormones

chemicals that are produced by a gland and carried in the blood, which alter the activities of their specific target organs

Vasoconstriction

narrowing of arterioles, caused by the contraction of the muscle in their walls

Carpel and its parts

female part; stigma, style, ovary, ovule

LH

Luteinising hormone, secreted by the pituitary gland and causes ovulation

Chromosome

a length of DNA, found in the nucleus of a cell; it contains genetic information in the form of many different genes

Mutation

a random change in a gene, which can produce new alleles; a change in the base sequence in DNA

Nitrification

converting ammonium ions to nitrate ions

Artificial Insemination

introducing semen, containing sperm, to the reproductive organs of a female; fertilisation occurs in her body in the normal way

Recombinant plasmid

a small circle of DNA, found in bacteria, which contains both the bacterial DNA and DNA from a different organism