A-level Biology: All key terms

Abiotic components

Components of an ecosystem that are non living

Abiotic factors

Non living components of an ecosystem that effect other living organisms

Acetycholine

Chemical that acts as a transmitter that diffuses across synaptic cleft

Acetycholinesterase

Enzyme in synaptic cleft that breaks down acetycholine. After it has triggered an action potential in the post synaptic neurone, acetycholine must be broken down otherwise it would remain in the synaptic cleft and continue to open sodium ion channels in the post synaptic membrane causing action potentials

Acinus (plural acini)

Small group of exocrine cells in a sac like structure. in the pancreas these surround a tubule and secrete into the tubule

Action potential

A brief reversal of teh potential across the membrane of a neurone causing a peak of +40mV compared to the resting potential of -60mV

Adenyl cyclase

An intracellular enzyme that converts ATP to cyclic AMP (CAMP)

ADP

Adenosine diphosphate

Adrenal cortex

Outer layer of the adrenal gland

Adrenal gland

One of the pair of glands lying above kidneys, which release adrenaline and a number of hormones known as corticoids (or corticosteroids) such as aldosterone

Adrenaline

Hormone released from medulla of adrenal glands which stimulates body to prepare for fight or flight

Adrenal medulla

Inner layer of adrenal gland

Adrenocorticotropic hormone (ACTH)

Hormone released by pituitary gland which stimulates adrenal cortex to produce corticosteroid hormones

Actin and myosin

Proteins involved in muscular contraction

Agar

Polysacharide of galactose obtained from seaweed which is used to thicken a medium into a gel.

Agarose

Type of sugar that can incorporated into a type of agar gel

Alkaloids

Organic nitrogen containing bases that have important physiological effects on animals, includes nicotine, quinine, strychnine and morphine

Allele

Version of a gene

Allele frequency

Propotion of a particular allele within the gene pool

Allopatric speciation

Formation of 2 different species from one original one due to geographic isolation

Alpha cells

Cells found in islets of langerhans that secrete glucagon

Ammonification

Production of ammonia by bacterial action in the decay of nitrgenous organic matter

AMP

Adeonside monophosphate

Aneuploidy

Abnormal chromosome number

Antagonist

Something that works against the other in opposite pairs, such as in the muscles that are arranged in opposing pairs, so one contracts and the other elongates

ADH (antidiuretic hormone)

Hormone made in hypothalamus, stored and released from pituitary gland, that controls permeability of collecting duct in walls of kidneys

Apical dominance

Inhibition of lateral buds fruther down shoot by chemicals produced by apicial bud at tip of plant shoot.

Apoptosis

Programmed cell death

Artificial selection

Selective breeding of organisms to produce desired phenotypes

Ascending limb

Part of loop of Henle that carries fluid back into distal tubule in cortex

ATP

Adenosine triphosphate

Autoimmune response

Response in which body's immune system attacks and destroys some of its own cells.

Autonomic nervous stsrem

Part of nervous system responsible for controlling involuntary motor activities of body

Autoradiograms

Photographs made when photographic film is exposed to molecules labelled with radioactivity

Autosomal linkage

Gene loci present on the same autosome (non sex chromosome) are often inherited together

Autosome

Chromosome not concerned with sex determination

Autotrophic nutrition

Nutrition where organic molecules are synthesised from inorganic molecules, i.e carbon dioxide and water. I.e photosynthesis where sunlight energy converted to chemical energy to synthesise large organic molecules from smaller inorganic ones. Chemosynthesis uses energy derived from chemical reactions (e.g nitrifying bacteria in soil)

Auxins

E.g IAA (indole 3 acetic acid)

Promotes cell elongation

Inhibits leaf abcission

Inhibits growth of side shoots- maintains apical dominance

Involved in tropisms

Stimulates release of ethene

Involved in food ripening

Cytokines

Promotes cell division

Leaf expansion

Delays leaf senescense

Overcomes apicial dominance

Ethene

Promotes food ripening

Promotes abscission in deciduous trees

Abscisic acid

Causes stomatal clouse when plant is streed by low water availabliity

Inhbits seed germination and growth

Stimulates cold protective responses I.e production of antifreeze

Gibberelins

Promotes seed germination and growth of stems

Triggers mobilisation of food stores in seed at germination

Stimulates pollen tube growth in fertilisation

Belt transcer

Continous belt or series of quadtrats used to estimate distribtion of organisms across a certain area such as a meadow or seashore.

Beta cells

Found in islets of langerhans in pancreas and release insulin

Bioinformatics

Branch of biology that deals with storing, displaying and using large quantities of complex data

Biomass transfer

Transfer of biomass from one trophic level to another

Biotechnology

Use of living ogrnaisms or part of living organisms in industrial processes. Could be to produce food, drugs or other products

Biotic compoentns

Living components of an ecoystsem

Biotic factors

Environemtnal factors associaed with living organisms in an ecosystem that affect each other, e.g predation, disease, competition and food availiability

Blunt ends

Cut ends of DNA where there are no staggered cut and no exposed unpaired bases

Cardiac muscle

Muscle found in heart walls

Cardiovascular centre

Part of medulla oblonata in brain that controls heart rate and other aspects of circulation

Carotid sinus

Small swelling in cartoid artery with stretch receptors in its walls

carrying capacity

Maximum population size that can be maintained over a period of time in a particular habittat

Caesin

Protein in milk

Cell signalling

Way in which cells communicate with each other

CNS

Central part of nervous system composed of brain and spinal cord

Cerebellum

Region of brain coordinating balance and fine control of movement

Cerebral cortex

Outer layer of cellebrum

Cerebrum

Region of brain dealing with higher thought processes such as conscious thought, divided into 2 cerebral hemispheres

Chemoautotrophic bacteria

Bacteria that derive energy from oxidation of certain inorganic compounds

Chemoreceptors

Sensory receptors that detect changes in cocnentration of chemical, e.g in blood. They transduce a chemical signal into an electrical signal.

Chemotropism

Directional growth response, in plants, to chemicals

Chi- squared test

Statistical test to find out if difference between observed and expected data is significant or due to chance

Cholinergic synapse

Synapse that uses acetycholine as neurotransmitter

Climax community

Final stable community that arises after process of succession.

Codominance

Where both alleles present in genotype of heterozygous invididual contributes to individuals phenotype

Coenzymes

Organic non protein molecules that act as cofactors which aid in catalysing biochemical reactions

Community

Populations of different species living in same place and time that can interact with each other

Conservation

Maintenance of biodiversity including genetic, speicies and habitat divserity

Conserved

Has remained in all descendent species throughout evolutionary history

Consumers

Any of heterophobic organisms in food chain or web; primary consumers feed on plants, eaten be secondary consumers which are eaten by tertiary consumers

Continuous variation

Variation that produces phenotypic variation where quantitative traits vary by very small amounts between one group and next

Coppicing

Cutting tree trunk close to ground to encourage new growth

Corneal reflex

Protective blinking response resulting from physiological stimulation of cornea

Corpus callosum

Nerve tract that connects cerebral hemispheres of brain

Corticotropin releasing hormone (CRH)

Known as cotricotropin releasing factor, hormone that causes release of adrencotricotropic hormone from pituitary gland

Cranial reflex

Reflex mediated by neurones that pass into brain

Creatine phosphate

Organic compound in muscle that acts as a store of phosphates and can supply phosphates to make ATP rapidly within mucle cells

Cristae

Inner folded mitochondrial membrane

Cyclic AMP (cAMP)

Secondary messenger released inside cells to activate a response

Cyclic changes

Rhythmic changes, such as tides, day length, and fluctuations in predator and prey species

Dark band

In stritated muscle also known as the A band which shows the length of the mysoin filaments; there is some overlap with the actin filaments within this band.

Death phase

Population size is decreasing as cells are dying faster than new ones are formed

Decomposers

Living organisms that feed on waste or dead organic matter

Deflected succession

When succession is stopped or interfered with such as by grazing or when a lawn is mowed