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All 10 Flashcards — Variation: the raw material
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Question
What is variation?
Answer
The **differences** that exist between **individuals of the same species**.
Question
Which kind of variation is the raw material for evolution?
Answer
**Heritable** variation — differences caused by **alleles** that can be passed to offspring.
Question
What are the three sources of heritable variation?
Answer
**Mutation**, **meiosis** (crossing over + independent assortment) and **random fertilisation**.
Question
What is a mutation?
Answer
A **random change in the DNA base sequence** — the only source of brand-new alleles.
Question
Which source makes NEW alleles, and which only SHUFFLE existing ones?
Answer
**Mutation** makes new alleles. **Meiosis** and **random fertilisation** shuffle existing alleles into new combinations.
Question
How does sexual reproduction increase variation?
Answer
It produces **new combinations** of **existing alleles** (via meiosis and random fertilisation) — not new alleles.
Question
Why is only germ-line (gamete) variation heritable?
Answer
Only mutations in **gametes / gamete-forming cells** are **passed to offspring**; somatic (body-cell) mutations are not.
Question
Are most mutations beneficial?
Answer
No — most are **neutral or harmful**; only **occasionally** is one beneficial in a given environment.
Question
Why is mutation called the 'ultimate source' of variation?
Answer
It is the **only** process that creates **genuinely new alleles**; everything else just re-combines existing ones.
Question
Distinguish continuous and discontinuous variation.
Answer
**Continuous** = a smooth range (e.g. height), often many genes + environment. **Discontinuous** = distinct categories (e.g. blood group), usually one/few genes.
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Natural selection
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