A2 Biology Key Words and Definitions.

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  • Created by: Molly
  • Created on: 07-05-14 10:29
What is an abiotic factor? Give an example.
An environmental factor that makes up part of the non-biological environment of an organism. EG rain, pH, humidity.
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What is acetylcholine?
A neurotransmitter that is released by a neurone and which crosses the synapse of two neurones to pass on a nerve impulse.
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What is an action potential?
A change that occurs in the electrical charge across the membrane of an AXON when it is stimulated and a nerve impulse passes.
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What is actin?
A filamentous protein which is involved in contraction within cells, especially muscle cells.
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What is activation energy?
The energy required to bring about a chemical reaction. The activation energy is lowered by enzymes.
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What is active transport?
The movement of a substance against a concentration gradient which requires energy in the form of ATP.
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What is ATP?
Adenosine triphosphate. An activated nucleotide found in all living cells that acts as an energy carrier.
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What is ADP?
Adenosine Diphosphate. A hydrolysed ATP molecule.
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What is adrenaline?
A hormone produced by the ADRENAL glands in times of stress that prepares the body for an emergency.
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What does aerobic mean?
In the presence of oxygen.
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What is an allele?
One form of a gene.
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What does allele frequency mean?
The number of times an allele occurs within a gene pool.
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What is an allergen?
A normally harmless substance that causes the immune system to produce an immune response.
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What does anaerobic mean?
The absence of oxygen.
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What is antibiotic resistance?
The development in populations of organisms of mechanisms that prevent antibiotics from kiling them.
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What is an antibody?
A protein produced by lymphocytes in response to the presence of a certain antigen.
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What is the autonomic nervous system?
Part of the nervous system that controls the muscles and glands which is not under voluntary control.
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What is an axon?
A process extending from a neurone that conducts action potentials away from the cell body.
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What is biodiversity?
The range and variety of living organisms within a particular area.
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What is biomass?
The total mass of living material in a specific area at a given time. It is usually measured as dry mass because the amount of water in an organism is variable.
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What is a biotic factor?
An ecological factor that makes up the biological part of the living environment of an organism. EG predation, food availability, competition.
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What is the calvin cycle?
A biochemical pathway that forms part of the light-independant reaction of photosynthesis, during which CO2 is reduced to form carbohydrates.
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What is cardiac muscle?
Muscle that is found only in the heart. It has fewer striations than skeletal muscle and can contract continously throughout life without stimulation by nerve impulses.
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What is a clone?
A group of genetically identical organisms formed from a single parent as a result of asexual reproduction or by artificial means.
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What is cholinesterase?
An enzyme that breaks down and inactivates the neurotransmitter acetylcholine.
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What is a climax community?
The organisms that make up the final stage of ecological succession.
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What is co-dominance?
A condition in which both alleles for ONE gene in a heterzygous organism contribute to their phenotype.
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What is a codon?
A sequence of three adjacent nucleotides in mRNA that codes for one amino acid.
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What is an anticodon?
A sequence of three adjacent nucleotides on a moleculeof transfer RNA that is complimentary to a particular codon on a messenger RNA molecule.
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What is a community?
The organisms of all species that live in the same area.
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What is a condensation reaction?
A chemical process in which two molecules are combined with the removal of water.
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What is conservation?
a method of maintaining ecosystems and the living organisms that occupy them.
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What is a consumer?
An organism that obtains energy by eating another organism. Organisms that eat on plants are primary consumers, organisms that eat primary consumers are secondary consumers.
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What is continous variation?
Variation in which organisms do not fall into distinct categories, but rather there are gradations from one extreme to the other. E.G. Height in humans.
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What is a cuticle?
An exposed non cellular outer layer of certain animals and plants, it is waxy and permeable to water so reduces water loss.
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What is cystic fibrosis?
A genetic disorder where the body produces abnormally thick mucus that obstructs breathing passages and prevents secretion of pancreatic enzymes. It is a recessive condition that leads to production of a non functioning membrane protein.
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What does decidious mean?
Term applied to plants that shed all their leaves together at one season.
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What is denaturation?
Permanent changes to the structure of a protein due to changes in temperature or pH.
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What is a dendrite?
A process, usually branched, extending from the cell body of a neurone which conducts impulses towards the cell body.
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What is denitrifying bacteria?
Bacteria that converts nitrates in to nitrogen gas as part of the nitrogen cycle.
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What is depolarisation?
A temporary reversal of charges on the cell-surface membrane of a neurone that takes place when a nerve impulse is transmitted.
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What is diabetes?
A metabolic disorder in which the body is unable to regulate the levels of glucose. There are two types/
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What is type 1 diabetes?
When the body is unable to produce insulin.
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What is type 2 diabetes?
When the body loses its responsiveness to insulin.
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What is a diploid?
A term applied to cells in which the nucleus contains two sets of chromosomes.
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What is directional selection?
Selection that operates towards one extreme in a range of variation.
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What is discontinuous variation?
Variation shown when the characteristics of an organism fall into distinct categories e.g. blood groups.
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What is DNA helicase?
An enzyme that acts on a specific region of a DNA molecule and breaks the hydrogen bonds between bases causing them to separate and expose the nucleotide bases in that region.
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What is DNA replication?
The process in which the double helix of DNA unwinds and each strand acts as a template for DNA polymerase to construct a new strand.
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What is a dominant allele?
A term applied to an allele that is always expressed in the phenotype of an organism.
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What is an ecological niche?
All conditions and resources required for the survival of an organism.
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What is an ecosystem?
Self-contained functional unit in ecology made up of all the interacting biotic and abiotic factors in a specific area.
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What is an ectotherm?
An organism that uses the environment to regulate its body temperature.
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What is an effector?
An organism that responds to stimulation by a nerve impulse resulting in a change or response.
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What is an electron?
A negatively charged subatomic particle that orbits the positively charged nucleus of an atom.
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What is an electron carrier molecule?
A chain of carrier molecules along which electrons pass, releasing energy in the form of ATP when they do so.
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What is an endotherm?
An animal that maintains its own body temperature by physiological mechanisms.
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Card 2


What is acetylcholine?


A neurotransmitter that is released by a neurone and which crosses the synapse of two neurones to pass on a nerve impulse.

Card 3


What is an action potential?


Preview of the front of card 3

Card 4


What is actin?


Preview of the front of card 4

Card 5


What is activation energy?


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