Variation and natural selection
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Flip to reveal answersName the three sources of heritable variation.
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All 12 Flashcards — Variation and natural selection
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Question
Name the three sources of heritable variation.
Answer
**Mutation**, **meiosis** and **sexual reproduction**.
Question
Which source creates brand-new alleles?
Answer
**Mutation** — a random change to DNA. (Meiosis and sexual reproduction only make new combinations.)
Question
Define natural selection.
Answer
The process where individuals **best suited to the environment survive and reproduce more**, passing on their alleles.
Question
Define evolution.
Answer
A **change in the heritable characteristics (allele frequencies)** of a population over many generations.
Question
Why must variation be heritable to drive natural selection?
Answer
Only **gene-based (allele)** variation can be **passed to offspring**; traits gained during life are not inherited.
Question
What is an adaptation?
Answer
An **inherited feature** that makes an organism **better suited to its environment**.
Question
What is the 'outcome' of natural selection?
Answer
A **favourable allele becomes more common** in the population over generations.
Question
Does the environment create the helpful variation?
Answer
**No** — the variation is **already present** (mostly from past mutations); the environment only **selects** it.
Question
Why is competition important for natural selection?
Answer
More offspring are produced than can survive, so individuals **compete** — the best-suited ones win out and reproduce.
Question
How does antibiotic resistance spread in bacteria?
Answer
A few bacteria already carry a **resistance allele** (mutation); the antibiotic kills the rest; survivors **reproduce** and the allele becomes **more common**.
Question
What does 'differential survival' mean?
Answer
Some individuals **survive and reproduce more than others** because of their heritable features.
Question
Define allele frequency.
Answer
How **common a particular allele is** in a population.
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Topic 1.8 hub
Evolution and speciation
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