Adaptive radiation as a source of biodiversity
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Question
Define speciation.
Answer
The **formation of a new species** from an existing one.
Question
Define adaptive radiation.
Answer
The **rapid evolution of many new species** from a single ancestor, each adapted to a **different niche**.
Question
What is a niche?
Answer
The particular **role and way of life** of a species — what it eats, where it lives and how it behaves.
Question
Adaptive radiation often follows what event?
Answer
Reaching **new, empty habitats** (for example a fresh island chain) with many unfilled niches.
Question
On a graph, what signals adaptive radiation?
Answer
A **sharp rise in the number of species** in one group over a relatively short time.
Question
Define gradual speciation.
Answer
Speciation by the **slow build-up of small heritable changes** over a long time.
Question
Define abrupt speciation.
Answer
Speciation that happens **suddenly**, over a short time (for example by a **chromosome-number change**).
Question
In the fossil record, what does gradual speciation look like?
Answer
A **smooth series of in-between forms**, each only slightly different from the one before.
Question
Give one common cause of abrupt speciation in plants.
Answer
A **change in chromosome number**, which instantly stops the plant breeding with its parent population.
Question
Do these patterns still need natural selection?
Answer
**Yes** — adaptive radiation, gradual and abrupt speciation all rely on **natural selection** and **reproductive isolation**.
Question
What does diversification mean here?
Answer
One group **becoming more varied** — splitting into **many** different species over time.
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Topic 1.8 hub
Evolution and speciation
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