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24 Cards in this Set
- Front
- Back
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What is a population?
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A population is a group of organisms of the same species living together in a particular place at a particular time.
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What is a species?
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A species is a group of individuals that share many characteristics and are able to interbreed to produce fertile offspring.
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What is the 'gene pool'?
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The sum of all alleles in a given population.
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What is the allele frequencies?
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How often each allele of a gene occurs in a population.
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What is a mutation?
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A new variation in offspring that shows no resemblence to either parent, may occur suddenly and by chance.
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What are the two types of mutations?
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Gene mutations, changes in a single gene so that the traits normally produced are changed or destroyed, and Chromosome mutations, all or part of a chromosome is affected.
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What is natural selection?
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The selection of favourable alleles. Nature favours the set of alleles that will produce the best chance of survival and reproduction.
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What is random genetic drift?
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A random non-directional variation in allel frequencies, occurs in small populations.
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What is the founder affect?
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When a small group moves away from its homeland to a new area and establishes a community. The group is not genetically representative of the original population and shows genetic features that are not typical of the original population.
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What is migration?
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The gene flow from one population to another. If immigrants to a certain country bring alleles that are not already in the population, the frequencies for the alleles of that allele will be altered.
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What are the two types of barriers to gene flow?
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Geographical barriers include oceans, mountain ranges, lake systems, deserts, ice sheets. Sociocultural barriers include economic status, educational background and social positions.
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What happens to alleles causing fatal genetic disease?
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They are gradually eliminated from the gene pool because people with the disease would die and not pass it on.
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What is Tay-Sachs disease?
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A hereditary disorder where the subject is missing an enzyme that results in the accumulation of fat in the nervous system. Death occurs at age 4 or 5. Individuals with a recessive allele for TSD has a increased resistance to tuberculosis.
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What is sickle-cell anaemia?
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A disease which causes red blood cells to be crescent shaped which results in an inability to carry enough oxygen.
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What is sickle-cell trait?
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When an individual has only one allele for sickle-cell anaemia. It provides a degree of immunity to malaria.
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Who put forward the theory of evolution through natural selection?
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Charles Darwin and Alfred Russel Wallace.
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What did Charles Darwin do?
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Went to Gallapagos islands and gathered evidence for natural selection, compiled research.
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What did Carolus Linnaeus do?
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Established the basis of classification and the binomial system of naming using generic (genus) and specific (species) names.
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What did Charles Lyell do?
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Put forward the hypothesis that natural forces existing in the past are the same as those today and they moulded the environment. Provided Darwin with a concept of constant change to base his work on.
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What did Thomas Malthus do?
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Realised that populations increased at a rate that exceeded the rate of food production. Thus a struggle for survival of the fittest would ensue resulting in the strongest, most favourable, species surviving.
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What are the three bases for natural selection?
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Variation - All members of a species vary and these variations are passed on from one generation to the next.
Birth rate - All living organisms reproduce at a rate freater than their available food supply which would normally result in overcrowding. Natures balance - Although the birth rate of organisms is very high each species maintains its numbers at relatively the same level. |
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What are Darwins enterpretations of the data he found?
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1. Due to high birth rates and limited resources there is a struggle for survival.
2. Due to the range of variations in a species the members with characteristics best suited to the environment were more likely to survive (survival of the fittest). |
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What is todays explanation of natural selection?
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The selection of the alleles in a population that give an organism a greater chance of survival. The organims that survive will pass on their alleles thus over time the characteristics of a population will change to suit its environment.
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What are the 4 stages of speciation?
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Variation (variations exist within a population), isolation (a barrier forms dividing the population), selection (different selection pressures are present resulting in different gene frequencies) and speciation (changes in the gene frequencies eventually result in loss of the ability to interbreed thus creating a new species).
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