IGCSE生物复习glossary.doc

Glossary

abdomen
lower part of the body in humans, between the ribs and hip bones
absorption
movement of digested food molecules through the wall of the intestine into the blood or lymph
acid rain
Air pollution produced when acid chemicals are incorporated into rain, snow, fog or mist. The "acid" in acid rain comes from sulfur oxides and nitrogen oxides, products of burning coal and other fuels and from certain industrial processes.
active transport
movement of ions in or out of a cell through the cell membrane, from a region of their lower concentration to a region of their higher concentration against a concentration gradient, using energy released during respiration
adaptation
features of living things that help them survive in their environment
aerobic respiration
the release of a relatively large amount of energy in cells by the breakdown of food substances in the presence of oxygen
alimentary canal
the passage along which food passes through the body, from mouth to anus
allele
one of two or more alternative forms of a gene
alveoli
air sacs in the lungs through which gas exchange takes place
amino acid
the basic building block of proteins
amnion
the innermost membrane enclosing the embryo
amniotic fluid
the fluid surrounding the developing fetus that is found within the amniotic sac contained in the mother's womb
amylase
a digestive enzyme, produced largely by the pancreas and salivary glands, which converts starches to sugars
anaemia
below normal levels of red blood cells or haemoglobin, or both, which can be caused by many different conditions, including iron deficiency
anaerobic respiration
the release of a relatively small amount of energy by the breakdown of food substances in the absence of oxygen
anther
pollen-producing oval body at the tip of a stamen
antibiotic
a class of natural and synthetic compounds that inhibit the growth of, or kill, other micro-organisms
antioxidant
a molecule that is capable of reacting with free radicals and neutralising them
anus
the opening to the anal canal
aorta
the largest artery; it leaves the heart
artery
blood vessel that carries blood away from the heart
arteriole
small, elastic blood vessel that arises from arteries and leads into capillaries
artificial selection
selective breeding
asexual reproduction
the process resulting in the production of genetically identical offspring from one parent
assimilation
making use of molecules that have been absorbed from food
atom
a chemical unit that is the smallest particle of an element still retaining its properties
auxin
a type of plant hormone that elongates cells in seedlings, shoot tips, embryos and leaves
axon
part of a neurone that allows electrical signals to pass through
bacteria
very small single-celled organisms
bile
a liquid produced by the liver that helps in digestion of fats
bile duct
the passage from the liver to the duodenum
bile salts
salts in the bile that help break fat into tiny droplets
binomial
a system in which the scientific name of an organism is made up of two parts showing the genus and species
biodegradable
able to be broken down by bacteria and other micro-organisms
biomass
the mass of a living organism
bolus
a ball of food
bronchi
tubes through which air passes, between the trachea and the smaller bronchioles
bronchioles
small tubes that branch from each of the bronchi
canines
pointed teeth used for biting
capillaries
tiny blood vessels
carbohydrase
enzyme that digests carbohydrate
carbon dioxide
gas produced during respiration and used up during photosynthesis
carnivore
an animal that gets its energy by eating other animals
catalyst
a substance that speeds up a chemical reaction and is not changed by the reaction
cell wall
the outer part of a plant cell, made of cellulose
cell
the basic ‘building block’ of living things
cervix
the neck of the womb
chlorophyll
green pigment in plants, involved in photosynthesis
chloroplasts
structures containing chlorophyll
chromosome
a thread of DNA, made up of a string of genes
ciliary muscles
ring of muscles holding the eye lens
codominant
alleles both having an effect in a heterozygous organism
colon
first part of the large intestine
community
all the different species in a habitat
concentration gradient
a difference in concentration across a material
cones
light-sensitive cells in the retina, responsible for colour vision
consumer
an organism that gets its energy by feeding on other organisms
contraction
in muscle tissue, the shortening of cells
cornea
the front of the eye, responsible for most of the focusing
coronary heart disease
disease in which the coronary arteries get blocked or damaged
coronary arteries
arteries that deliver blood to the heart muscles
crustaceans
a group of arthropods including crabs, shrimp and woodlice
cytoplasm
jelly-like substance in cells
deamination
removal of nitrogen from amino acids
decomposers
an organism that gets its energy from dead or waste organic matter
deficiency disease
disease caused by lack of a particular nutrient
denaturing
breakdown of an enzyme caused by a high temperature
dendrites
threads of cytoplasm in a neurone that pick up electrical signals
denitrifying bacteria
bacteria that turn ammonia and nitrates back to nitrogen
dialysis
filtering a patient’s blood in a similar way to a kidney
diaphragm
muscular sheet below the ribs and lungs
diffusion
the net movement of molecules from a region of their higher concentration to a region of their lower concentration down a concentration gradient, as a result of their random movement
digestion
the breakdown of large, insoluble food molecules into small, water-soluble molecules using mechanical and chemical processes
diploid nucleus
a nucleus containing two sets of chromosomes (e.g. in body cells)
DNA
deoxyribonucleic acid, the molecule from which genes are composed
dominant
an allele that is expressed if it is present (e.g. T or G)
double circulatory system
a system in which the blood goes through the heart twice
drug
any substance taken into the body that modifies or affects chemical reactions in the body
duodenum
first part of the small intestine
ecosystem
a unit containing all of the organisms and their environment, interacting together, in a given area e.g. decomposing log or a lake
effectors
parts of the body that respond to changes
egestion
passing out of food that has not been digested through the anus as faeces
embryo
an unborn offspring during the first eight weeks after conception
emphysema
condition of the lungs causing breathlessness
endocrine system
communication system that uses hormones
enzymes
proteins that function as biological catalysts
epidermis
layers of cells at the surface of a leaf
eutrophication
lack of oxygen in water caused by excessive plant nutrients
evolution
process by which different kinds of organism develop from earlier ones
excretion
removal from organisms of toxic materials, the waste products of metabolism (chemical reactions in cells including respiration) and substances in excess of requirements
exoskeleton
hard outer covering of the body
faeces
waste products of digestion
Fallopian tube
tube leading from the ovary to the uterus, through which an egg must pass
fatty acids
part of a fat molecule
fertilisation
process by which a sperm combines with an egg
fetus
an unborn offspring after the first eight weeks after conception
fibre
roughage in the diet
fibrin
an insoluble protein that gets tangled up with blood cells to produce a blood clot
fibrinogen
a soluble protein in blood plasma
food chain
a chart showing the flow of energy (food) from one organism to the next, beginning with a producer (e.g. mahogany tree → caterpillar → song bird → hawk)
food web
a network of interconnected food chains showing the energy flow through part of an ecosystem
fossil fuels
fuels such as coal, oil and gas formed from remains of living things that existed millions of years ago
gall bladder
bile is stored in the gall bladder
gametes
male or female germ cell (a sperm or egg)
gastric juice
fluid that mixes with food in the stomach
genes
A length of DNA that is the unit of heredity and contains codes for a specific protein. A gene may be copied and passed on to the next generation.
genetic engineering
taking a gene from one species and putting it into another species
genotypes
genetic makeup of an organism in terms of the alleles present (e.g. Tt or GG)
geotropism
a response in which a plant grows towards or away from gravity
glucagon
hormone that increases blood glucose concentration
glucose
a type of sugar
glycogen
a polysaccharide, used as an energy store
growth
a permanent increase in size and dry mass, by an increase in cell number or cell size, or both
guard cells
in a leaf, the guard cells change shape to open or close the stomata
haemoglobin
a protein in blood, responsible for carrying oxygen
haploid nucleus
a nucleus containing a single set of unpaired chromosomes (e.g. sperm and egg)
herbivore
an animal that gets its energy by eating plants
hermaphrodite
having both male and female characteristics
heterozygous
having two different alleles of a particular gene (e.g. Tt or Gg), not pure-breeding
homeostasis
the maintenance of a constant internal environment
homozygous
Having two identical alleles of a particular gene (e.g. TT or gg). Two identical homozygous individuals that breed together will be pure-breeding.
hormones
a chemical substance, produced by a gland, carried by the blood, which alters the activity of one or more specific target organs and is then destroyed by the liver
hyphae
threads making up the main body of a fungus
ileum
latter part of the small intestine
immunosuppressant drugs
substance taken into the body that modifies or affects chemical reactions in the body
incisors
biting teeth
ingestion
taking substances (e.g. food, drink) into the body through the mouth
inheritance
the transmission of genetic information from generation to generation
inorganic
substances that do not derive from living things
insulin
hormone that helps reduce a high blood glucose level
intercostal muscles
muscles between the ribs
iris
coloured part of the eye that changes shape to control amount of light entering the eye
kidney tubules
tiny tubes in the kidney that play a role in filtering the blood
kwashiorkor
condition caused by lack of protein in the diet
lactase
enzyme that breaks down lactose
lactic acid
a waste product of anaerobic respiration
lactose
a type of sugar
large intestine
part of the intestine where remaining water and inorganic ions pass into the blood
limiting factor
something present in the environment in such short supply that it restricts life processes
lipases
enzymes that break down fats
lipids
an alternative name for fats
lumen
space in the veins through which blood flows
lymph
tissue fluid in the lymphatic capillaries
lymphocytes
white blood cells that kill pathogens
malaria
disease caused by a parasite carried by mosquitoes
maltase
enzyme that breaks down maltose
maltose
a type of sugar
meiosis
reduction division in which the chromosome number is halved from diploid to haploid
menstrual cycle
process of menstruation and ovulation
menstruation
discharge of blood from the lining of the uterus
mesophyll
inner tissue of a leaf
metabolic reactions
chemical reactions that take place in cells
micropyle
small opening in the surface of an ovule
mitosis
nuclear division giving rise to genetically identical cells in which the chromosome number is maintained by the exact duplication of chromosomes
molars
grinding teeth
mutation
a change in a gene or chromosome
mycelium
the main body of a fungus
myriapod
an arthropod with many legs
narcotic
addictive drug
nerve cell
cell that carries electrical signals
neurone
alternative name for a nerve cell
nicotine
addictive drug found in tobacco
nitrifying bacteria
bacteria that change proteins in organic material into ammonia and nitrates
nitrogen-fixing bacteria
bacteria that change nitrogen from the air into ammonia
nucleus
part of a cell that contains genetic material
nutrition
taking in of nutrients that are organic substances and mineral ions, containing raw materials or energy for growth and tissue repair, absorbing and assimilating them
obesity
condition of being severely overweight
oesophagus
tube connecting mouth and stomach
oestrogen
hormone that controls development of female characteristics
optic nerve
nerve connecting retina to brain
organ
a structure made up of a group of tissues working together to perform specific functions
organ systems
a group of organs with related functions, working together to perform body functions
organic
derived from living things
osmosis
the diffusion of water molecules from a region of their higher concentration (dilute solution) to a region of their lower concentration (concentrated solution), through a partially permeable membrane
ovary
the organ in which eggs (ova) are produced
oviduct
tube through which an egg leaves the ovary
ovulation
process by which an egg is released from the ovary
ovules
part of the ovary of a plant; becomes the seed after fertilisation
oxygen debt
condition after exercise during which extra oxygen is needed to break down lactic acid
oxyhaemoglobin
molecule formed when haemoglobin combines with oxygen
palisade cells
cells near the surface of a leaf where most of the photosynthesis takes place
pancreas
gland containing pancreatic juice
pancreatic juice
fluid containing enzymes that help digestion
partially permeable
allowing some substances through, but not others
pathogen
a harmful organism
pectinase
enzyme that helps to break down cell walls in fruit
penicillin
an antibiotic
pepsin
a protein-digesting enzyme
peristalsis
process by which muscles in the wall of the intestine cause food to be pushed along
phagocytes
white blood cells that surround and digest harmful bacteria
phenotype
the physical or other features of an organism due to both its genotype and its environment (e.g. tall plant or green seed)
phloem tubes
tubes that transport sugars around a plant
photosynthesis
the fundamental process by which plants manufacture carbohydrates from raw materials using energy from light
phototropism
a response in which a plant grows towards or away from the direction from which light is coming
placenta
organ in the uterus that provides nutrients for the fetus
plasma
watery constituent of blood that contains many dissolved substances
plasmolysed
condition when the surface membrane of a plant cell is pulled away from the cell wall
pollination
the transfer of pollen grains from the male part of the plant (anther of stamen) to the female p