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IGCSE BIOLOGY KEY DEFINITIONS

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Cambridge IGCSE A* Biology
vbest.edu.my | MS JOAN YUEN
Chapter 1 Characteristics and classification of living organisms
KEY
movement
DEFINITION
ü an action by an organism or part of an organism
ü causing a change of position or place
respiration
ü the chemical reactions in cells
ü that break down nutrient molecules and release energy for
metabolism
sensitivity
ü ability to detect or sense stimuli in the internal or external
environment
ü and to make appropriate responses
growth
ü permanent increase in size and dry mass
ü by an increase in cell number or cell size or both
excretion
ü removal from organisms of the waste products of metabolism
(chemical reactions in cells including respiration),
ü toxic materials,
ü and substances in excess of requirements
nutrition
ü taking in of materials for energy, growth and development;
ü plants require light, carbon dioxide, water and ions;
ü animals need organic compounds and ions and usually need
water
species
ü group of organisms that can reproduce
ü to produce fertile offspring
binomial system
ü naming species as an internationally agreed system
ü in which the scientific name of an organism is made up of two
parts
ü showing the genus and species
KEY DEFINITION| Notes v3.18| Google: vbest
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Cambridge IGCSE A* Biology
vbest.edu.my | MS JOAN YUEN
Morphology
ü the study of the form, or outward appearance, of organisms.
Anatomy
ü the study of their internal structure, as revealed by dissection.
KEY DEFINITION| Notes v3.18| Google: vbest
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Cambridge IGCSE A* Biology
vbest.edu.my | MS JOAN YUEN
Chapter 2 Organisation of the organism
KEY
tissue
DEFINITION
ü a group of cells with similar structures,
ü working together to perform a shared function
ü Eg. Bone, nerve, muscle, epidermis, xylem
organ
ü a structure made up of a group of tissues,
ü working together to perform specific functions
ü Eg. Stomach, heart, lungs, intestines, brain, eyes
organ system
ü a group of organs with related functions,
ü working together to perform body functions
ü Eg. Nervous and circulatory system
Chapter 3 Movement in and out of cells
KEY
diffusion
DEFINITION
ü net movement of particles
ü from a region of their higher concentration to a region of their
lower concentration
ü down a concentration gradient,
ü as a result of their random movement
osmosis
ü
ü
ü
ü
net movement of water molecules
from a region of higher water potential (dilute solution)
to a region of lower water potential (concentrated solution),
through a partially permeable membrane
active transport
ü
ü
ü
ü
the movement of particles through a cell membrane
from a region of lower concentration
to a region of higher concentration
using energy from respiration
KEY DEFINITION| Notes v3.18| Google: vbest
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Cambridge IGCSE A* Biology
vbest.edu.my | MS JOAN YUEN
Chapter 5 Enzymes
KEY
catalyst
DEFINITION
ü a substance that increases the rate of a chemical reaction
ü and is not changed by the reaction
enzymes
ü proteins that function as biological catalysts
Chapter 6 Plant nutrition
KEY
photosynthesis
DEFINITION
ü the process by which plants manufacture carbohydrates
ü from raw materials using energy from light
limiting factor
ü something present in the environment
ü in such short supply that it restricts life processes
KEY DEFINITION| Notes v3.18| Google: vbest
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Cambridge IGCSE A* Biology
vbest.edu.my | MS JOAN YUEN
Chapter 7 Human nutrition
KEY
ingestion
DEFINITION
ü taking of substances
ü e.g. food and drink, into the body through the mouth
mechanical digestion
ü breakdown of food into smaller pieces
ü without chemical change to the food molecules
chemical digestion
ü breakdown of large, insoluble molecules
ü into small, soluble molecules
absorption
ü movement of small food molecules and ions
ü through the wall of the intestine into the blood
assimilation
ü movement of digested food molecules
ü into the cells of the body where they are used,
ü becoming part of the cells
egestion
ü passing out of food that has not been digested or absorbed,
as faeces, through the anus
Chapter 8 Transport in plants
KEY
transpiration
translocation
DEFINITION
ü loss of water vapour from plant leaves
ü by evaporation of water at the surfaces of the mesophyll cells
followed
ü by diffusion of water vapour through the stomata
ü movement of sucrose and amino acids in phloem:
ü from regions of production (source)
ü to regions of storage OR to regions where they are used in
respiration or growth (sink)
KEY DEFINITION| Notes v3.18| Google: vbest
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vbest.edu.my | MS JOAN YUEN
Cambridge IGCSE A* Biology
Chapter 10 Diseases and immunity
KEY
pathogen
DEFINITION
ü disease-causing organism
transmissible
disease
ü disease in which the pathogen
ü can be passed from one host to another
active immunity
ü defence against a pathogen
ü by antibody production in the body
Chapter 12 Respiration
KEY
aerobic respiration
DEFINITION
ü chemical reactions in cells
ü that use oxygen to break down nutrient molecules to
release energy
anaerobic respiration
ü chemical reactions in cells
ü that break down nutrient molecules to release energy
without using oxygen
Chapter 13 Excretion in humans
KEY
deamination
DEFINITION
ü the removal of the nitrogen-containing part of amino acids
ü to form urea
KEY DEFINITION| Notes v3.18| Google: vbest
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Cambridge IGCSE A* Biology
vbest.edu.my | MS JOAN YUEN
Chapter 14 Coordination and response
KEY
synapse
DEFINITION
ü a junction between two neurones
sense organs
ü groups of receptor cells
ü responding to specific stimuli: light, sound, touch, temperature
and chemicals
hormone
ü chemical substance,
ü produced by a gland and carried by the blood,
ü which alters the activity of one or more specific target organs
homeostasis
ü maintenance of a constant internal environment
gravitropism
ü response in which parts of a plant
ü grow towards or away from gravity
phototropism
ü a response in which parts of a plant
ü grow towards or away from the direction from which light is
coming
Chapter 15 Drugs
KEY
drug
DEFINITION
ü any substance taken into the body
ü that modifies or affects chemical reactions in the body
KEY DEFINITION| Notes v3.18| Google: vbest
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Cambridge IGCSE A* Biology
vbest.edu.my | MS JOAN YUEN
Chapter 16 Reproduction
KEY
asexual reproduction
DEFINITION
ü process resulting in the production of genetically identical
offspring
ü from one parent
sexual reproduction
ü process involving the fusion of the nuclei of two gametes
(sex cells)
ü to form a zygote
ü and the production of offspring that are genetically
different from each other
fertilisation
ü fusion of gamete nuclei
pollination
ü transfer of pollen grains from the anther to the stigma
self-pollination
ü transfer of pollen grains from the anther of a flower to the
stigma
ü of the same flower or different flower
ü on the same plant
cross-pollination
ü transfer of pollen grains from the anther of a flower to the
stigma
ü of a flower on a different plant of the same species
sexually transmitted
infection
ü infection that is transmitted
ü via body fluids through sexual contact
KEY DEFINITION| Notes v3.18| Google: vbest
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Cambridge IGCSE A* Biology
vbest.edu.my | MS JOAN YUEN
Chapter 17 Inheritance
KEY
inheritance
DEFINITION
ü transmission of genetic information
ü from generation to generation
chromosome
ü thread-like structure of DNA,
ü carrying genetic information in the form of genes
gene
ü length of DNA that codes for a protein
allele
ü a version of a gene
haploid nucleus
ü nucleus containing a single set of unpaired chromosomes,
ü e.g. in gametes
diploid nucleus
ü nucleus containing two sets of chromosomes,
ü e.g. in body cells
mitosis
ü nuclear division
ü giving rise to genetically identical cells
meiosis
ü reduction division
ü in which the chromosome number
ü is halved from diploid to haploid resulting in genetically
different cells
genotype
ü genetic make-up of an organism in terms of the alleles
present
phenotype
ü observable features of an organism
KEY DEFINITION| Notes v3.18| Google: vbest
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Cambridge IGCSE A* Biology
vbest.edu.my | MS JOAN YUEN
homozygous
ü having two identical alleles of a particular gene
heterozygous
ü having two different alleles of a particular gene
dominant
ü allele that is expressed if it is present
recessive
ü allele that is only expressed
ü when there is no dominant allele of the gene present
sex-linked
characteristic
ü characteristic in which the gene responsible is located on a
sex chromosome
ü and that this makes it more common in one sex than in the
other
Chapter 18 Variation and selection
KEY
variation
DEFINITION
ü differences between individuals
ü of the same species
gene mutation
ü a change in the base sequence of DNA
adaptive feature
ü inherited feature
ü that helps an organism to survive and reproduce
ü in its environment
fitness
ü the probability of an organism
ü surviving and reproducing in the environment in which it is found
adaptation
ü process, resulting from natural selection,
ü by which populations become more suited to their environment
over many generations
KEY DEFINITION| Notes v3.18| Google: vbest
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Cambridge IGCSE A* Biology
vbest.edu.my | MS JOAN YUEN
Chapter 19 Organisms and their environment
KEY
food chain
DEFINITION
ü showing the transfer of energy
ü from one organism to the next, beginning with a producer
trophic level
ü the position of an organism in a food chain, food web, pyramid
of numbers or pyramid of biomass
food web
ü a network of interconnected food chains
producer
ü an organism that makes its own organic nutrients,
ü usually using energy from sunlight,
ü through photosynthesis
consumer
ü an organism that gets its energy
ü by feeding on other organisms
herbivore
ü an animal that gets its energy
ü by eating plants
carnivore
ü an animal that gets its energy
ü by eating other animals
decomposer
ü an organism that gets its energy
ü from dead or waste organic material
population
ü a group of organisms of one species,
ü living in the same area, at the same time
community
ü all of the populations of different species in an ecosystem
KEY DEFINITION| Notes v3.18| Google: vbest
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Cambridge IGCSE A* Biology
ecosystem
vbest.edu.my | MS JOAN YUEN
ü a unit containing the community of organisms and their
environment
ü interacting together, e.g. a decomposing log, or a lake
Chapter 20 Biotechnology and genetic engineering
KEY
genetic engineering
DEFINITION
ü changing the genetic material of an organism
ü by removing, changing or inserting individual genes
Chapter 21 Human influences on ecosystems
KEY
sustainable resource
DEFINITION
ü one which is produced as rapidly
ü as it is removed from the environment
ü so that it does not run out
sustainable
development
ü development providing for the needs
ü of an increasing human population
ü without harming the environment
KEY DEFINITION| Notes v3.18| Google: vbest
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