9700 · 17.2
Natural and artificial selection flashcards
Revision flashcards for Cambridge 9700 Natural and artificial selection (syllabus 17.2). Flip, recall, then mark a real past-paper question.
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What is natural selection?
The process where organisms better adapted to their environment tend to survive and reproduce more successfully, leading to an increase in the frequency of advantageous alleles in a population over generations. The environment is the selective agent.
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What is artificial selection (selective breeding)?
The process where humans intentionally select and breed organisms with desirable traits to enhance those traits in subsequent generations. Humans are the selective agent.
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What is a 'selection pressure' in the context of evolution?
An environmental factor that affects an organism's ability to survive and reproduce. It 'drives' natural selection. Examples include predation, disease, competition for resources, climate change, and antibiotic presence.
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State the primary difference between the selective agents in natural and artificial selection.
In natural selection, the selective agent is the environment (biotic and abiotic factors). In artificial selection, the selective agent is humans, based on their preferences or needs.
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What is the main impact of artificial selection on a population's genetic diversity?
Artificial selection significantly reduces genetic diversity by selecting for a narrow range of alleles associated with desired traits and eliminating others from the gene pool.
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Define 'inbreeding depression'.
The reduced biological fitness in a population resulting from the breeding of related individuals. It increases the likelihood of offspring being homozygous for deleterious recessive alleles.
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Name the four key components of Darwin's theory of natural selection.
1. **Variation:** Individuals in a population vary. 2. **Overproduction:** More offspring are produced than can survive. 3. **Struggle for Existence:** Competition for limited resources. 4. **Differential Survival & Reproduction:** Individuals with advantageous traits are more likely to survive and pass them on.
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Give a modern example of rapid natural selection.
The evolution of antibiotic resistance in bacteria. When an antibiotic is applied, it acts as a strong selection pressure, killing susceptible bacteria and allowing resistant mutants to survive, reproduce, and dominate the population.