what is evolution?
the change over time in the proportion of individuals in a population differing in one or more inherited traits.
how does changes in allele frequency occur during evolution?
through the non-random processes of natural selection and sexual selection, and the random process of genetic drift.
what does natural selection act on in populations?
genetic variation.
how does variation in traits arise during natural selection?
as a result of mutation.
what is the original source of new sequences of DNA?
mutations.
what are the new sequences of DNA produced as a result of mutation called?
novel alleles.
what are the 3 classifications of mutations that affect the fitness of an individual?
harmful, neutral, and beneficial.
during natural selection, what is the relationship between populations producing offspring and the environmental support?
populations produce more offspring than the environment can support.
what occurs when individuals with variations are better suited to their environment?
they tend to survive longer and produce more offspring, breeding to pass on those alleles that conferred an advantage to the next generation.
give a definition of selection.
selection results in the non-random increase in the frequency of advantageous alleles and the non-random decrease in the frequency of deleterious alleles.
give a definition of sexual selection.
sexual selection is the non-random process involving the selection of alleles that increase the individual’s chances of mating and producing offspring.
what can sexual selection lead to?
sexual dismorphism.
what is sexual selection due to?
male-male rivalry and female choice.
what 2 features of males are used in male-male rivalry?
large size or weaponry.
what is the benefit of male-male rivalry?
increase access to females through conflict.
what does female choice involve?
females assessing the fitness of males.
when does genetic drift occur?
when chance events cause unpredictable fluctuations in allele frequencies from one generation to the next.
why is genetic drift more important in small populations?
as alleles are more likely to be lost from the gene pool.
Name 2 processes that can have an effect on genetic drift.
bottleneck effect
founder effect
when does the bottleneck effect occur?
when a population size is reduced for at least one generation.
when do founder effects occur?
through the isolation of a few members of a population from a larger population.
describe the founder effect in terms of gene pools of the new population and the original population.
the gene pool of the new population is not representative of that in the original gene pool.
why is a gene pool altered by genetic drift?
certain alleles may be under-represented or over-represented and allele frequencies change.
what occurs when selection pressures are strong?
the rate of evolution is rapid.
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2.1 Health and Safety5
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2.1 Sampling of Wild Organisms8
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2.1 Identification and Taxonomy16
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2.1 Monitoring Populations12
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2.1 Measuring and Recording Animal Behaviour10
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2.2 Drift and Selection31
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2.2 Fitness9
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2.2 Co-evolution10
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2.3 Costs and Benefits of Sexual and Asexual Reproduction25
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2.3 Meiosis21
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2.3 Sex Determination14
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2.4 Sex and Behaviour12
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2.4 Reproductive Behaviours and Mating Systems in Animals19
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2.5 Niche5
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2.5 The Parasite Niche7
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2.5 Parasitic Life Cycles28
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2.5 Transmission and Virulence10
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2.5 Defence against Parasitic Attack23
