The Ultimate IGCSE Bio-Dictionary – From Cells
to Ecosystems, Every Key Term Explained
Active transport - The movement of substances against a concentration gradient and/or across
a cell membrane using energy
Anti Diuretic Hormone - Hormone which controls the selective reabsorbtion of water in
Kidney
Aerobic Respiration - The process by which food molecules are broken down using oxygen
to release energy for the cells
Allele - A version of a partivular gene
Anaerobic respiration - Cellular respiration in the absence of oxygen
Asexual reproduction - Reproduction which involves only one parent and produces offspring
which are identical to their parents
Auxins - Plant hormones which are involved in controlling the phototropisms
Carbohydrates - Food group which includes the sugar and starches. They are important for
providing energy for the cells
Cell - Basic unit of all living organism
Cellular respiration - Respiration which takes place in the cytoplasm and mitochondria of the
cells
Cellulose cell wall - The rigid cell wall which surrounds plant cell
,Chlorophyll - The green pigment contained in the chloroplast which captures light energy
from the sun
Chloroplast - The plant organelles which contain chlorophyll. They are the site of
photosynthesis
Clone - Offspring produces by asexual reproduction which are identical to their parent
organism
Codominance - Two alleles which are both expressed in the phenotype of an
offspring
Consumers - Organisms which feed on other organisms, eg. Primary eats plants, secondary
consumers eat herbivores
Cytoplasm - The water-based gel in which the organelles of all living cells are
suspended
Decomposers - Microorganisms that break down water products and dead bodies
Denatures - The breakdown of the structure of a protein molecule if the temperature gets too
hot or the pH changes
Diastole - The stage of the cardiac cycle when the heart fills with blood-relaxation period of a
heart beat
Differentiate - The process by which unspecialised cells become specialised for a particular
function
Diffusion - The net movement of the particles of a gas or a solute from an area of high
concentration to an area of low concentration, down a concentration gradient
,Diploid - Having 2 sets of chromosomes in the nucleus of the cells: one from the male parent
and one from the female
Disperse - The spreading of seeds away from the parent plant to avoid competition.
Dominant - A characteristic which will show up in the offspring even if only one of the
alleles is inherited
Double circulation - The separate circulation of blood from the heart to the lungs and then
back to the heart again and from the heart to the body and back to the heart again
Ecosystem - All of the animals and plants living in an area, along with the things what affect
them, such as soil and the weather. An ecosystem includes all the interactions between the
many different types of living organisms and the non-living components
Egestion - The removal of undigested food from a cell or from the body in the form of
faeces
Endocrine glands - The glands which produce hormones and secrete them directly into the
blood
Enzyme - A protein molecule which acts as a biological catalyst, speeding up the rate of a
specific reaction without being used up or affected. Enzymes are sensitive to both
temperature an pH
Eutrophication - When a lake or a river becomes enriched with nutrients, e.g from fertiliser
applied to fields, excess plant growth is followed by decay. Microorganisms use up oxygen
from the water so that other organisms can no longer survive
, Fermentation - Another term for anaerobic respiration which is particularly used for
microorganisms such as yeast. Glucose is partly broken down into ethanol or lactic acid with
the release of a small amount of energy
Fertilisation - The joining of of the haploid male and female gametes to form a new diploid
individual
Gametes - The haploid sex cell which contain only one set of chromosomes. Male gametes
include sperm and pollen, female gametes include ova and ovules
Genetically modified organism - Organisms which have had DNA from a different species or
a different individual inserted in their genome
Genotype - The genetic makeup of an organism concerning the alleles of a particular gene.
e.g TT, Tt, tt
Global warming - An increase in the temperature at the surface of the earth due to green
house gases in the atmosphere trapping infrared radiation from the surface
Glycogen - The carbohydrate energy store found in the liver and muscles of animals. It can be
converted back into glucose when energy is needed in cells
Green house gases - Gases such as carbon dioxide and methane in the atmosphere which
absorb infrared radiation from the surface of the Earth and radiate from the surface of the
Earth and radiate it back to the surface, contributing to the greenhouse effect
Habitat - The place where an animal or plant lives including both the living and the non-
living aspects of the area
Haploid - Having only one set of chromosomes in the nucleus of the cell
to Ecosystems, Every Key Term Explained
Active transport - The movement of substances against a concentration gradient and/or across
a cell membrane using energy
Anti Diuretic Hormone - Hormone which controls the selective reabsorbtion of water in
Kidney
Aerobic Respiration - The process by which food molecules are broken down using oxygen
to release energy for the cells
Allele - A version of a partivular gene
Anaerobic respiration - Cellular respiration in the absence of oxygen
Asexual reproduction - Reproduction which involves only one parent and produces offspring
which are identical to their parents
Auxins - Plant hormones which are involved in controlling the phototropisms
Carbohydrates - Food group which includes the sugar and starches. They are important for
providing energy for the cells
Cell - Basic unit of all living organism
Cellular respiration - Respiration which takes place in the cytoplasm and mitochondria of the
cells
Cellulose cell wall - The rigid cell wall which surrounds plant cell
,Chlorophyll - The green pigment contained in the chloroplast which captures light energy
from the sun
Chloroplast - The plant organelles which contain chlorophyll. They are the site of
photosynthesis
Clone - Offspring produces by asexual reproduction which are identical to their parent
organism
Codominance - Two alleles which are both expressed in the phenotype of an
offspring
Consumers - Organisms which feed on other organisms, eg. Primary eats plants, secondary
consumers eat herbivores
Cytoplasm - The water-based gel in which the organelles of all living cells are
suspended
Decomposers - Microorganisms that break down water products and dead bodies
Denatures - The breakdown of the structure of a protein molecule if the temperature gets too
hot or the pH changes
Diastole - The stage of the cardiac cycle when the heart fills with blood-relaxation period of a
heart beat
Differentiate - The process by which unspecialised cells become specialised for a particular
function
Diffusion - The net movement of the particles of a gas or a solute from an area of high
concentration to an area of low concentration, down a concentration gradient
,Diploid - Having 2 sets of chromosomes in the nucleus of the cells: one from the male parent
and one from the female
Disperse - The spreading of seeds away from the parent plant to avoid competition.
Dominant - A characteristic which will show up in the offspring even if only one of the
alleles is inherited
Double circulation - The separate circulation of blood from the heart to the lungs and then
back to the heart again and from the heart to the body and back to the heart again
Ecosystem - All of the animals and plants living in an area, along with the things what affect
them, such as soil and the weather. An ecosystem includes all the interactions between the
many different types of living organisms and the non-living components
Egestion - The removal of undigested food from a cell or from the body in the form of
faeces
Endocrine glands - The glands which produce hormones and secrete them directly into the
blood
Enzyme - A protein molecule which acts as a biological catalyst, speeding up the rate of a
specific reaction without being used up or affected. Enzymes are sensitive to both
temperature an pH
Eutrophication - When a lake or a river becomes enriched with nutrients, e.g from fertiliser
applied to fields, excess plant growth is followed by decay. Microorganisms use up oxygen
from the water so that other organisms can no longer survive
, Fermentation - Another term for anaerobic respiration which is particularly used for
microorganisms such as yeast. Glucose is partly broken down into ethanol or lactic acid with
the release of a small amount of energy
Fertilisation - The joining of of the haploid male and female gametes to form a new diploid
individual
Gametes - The haploid sex cell which contain only one set of chromosomes. Male gametes
include sperm and pollen, female gametes include ova and ovules
Genetically modified organism - Organisms which have had DNA from a different species or
a different individual inserted in their genome
Genotype - The genetic makeup of an organism concerning the alleles of a particular gene.
e.g TT, Tt, tt
Global warming - An increase in the temperature at the surface of the earth due to green
house gases in the atmosphere trapping infrared radiation from the surface
Glycogen - The carbohydrate energy store found in the liver and muscles of animals. It can be
converted back into glucose when energy is needed in cells
Green house gases - Gases such as carbon dioxide and methane in the atmosphere which
absorb infrared radiation from the surface of the Earth and radiate from the surface of the
Earth and radiate it back to the surface, contributing to the greenhouse effect
Habitat - The place where an animal or plant lives including both the living and the non-
living aspects of the area
Haploid - Having only one set of chromosomes in the nucleus of the cell
