Life on Earth: Evolution Flashcards
What is a gene?
Section of a chromosome which codes for a protein.
What is an allele?
Different forms of a gene.
What is variation?
Differences between members of the same species.
What is a mutation?
A random change in genetic material.
What effect can a mutation have to survival?
Can be neutral, an advantage or disadvantage.
What can have an effect on the rate of mutations?
Radiation and some chemicals.
What is an adaptation?
An inherited characteristic that makes an organism well-suited to it’s environment/niche.
What is a selection pressure?
A factor that acts on members of a population and sometimes results in death for some population members and the survival of others.
Give 2 examples of selection pressures
- Competition
- Predation
- Disease
- Changes in climate
Describe natural selection
Species produce more offspring than the environment can sustain.
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Natural selection (survival of the fittest) occurs when there are selection pressures.
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The best adapted individuals in a population have characteristics which give them a selective advantage.
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This means they are more likely to survive and reproduce, passing on their favourable alleles that gave the selective advantage
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These favourable alleles increase in frequency in the population.
What is speciation?
The formation of new species from a common ancestor.
Describe stage one of speciation (isolation)
- The population is split by an isolation barrier.
- This isolation barrier is either geographical, ecological or behavioural.
Describe stage two of speciation (mutation)
- Different mutations will occur in each subpopulation.
- This means that the mutations will be different in each subpopulation.
- Some of these will be advantageous.
Describe stage three of speciation (natural selection)
- Natural selection selects for different mutations in each subpopulation due to different selection pressures.
Describe stage four of speciation (new species forming)
- Each subpopulation evolves until they become so genetically different that they can no longer interbreed to produce fertile offspring, thus they are now two different species.
