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All 14 Flashcards — Evidence for evolution
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Question
Define homologous structures.
Answer
Structures with the **same basic plan but different functions**, inherited from a **common ancestor** (e.g. human arm, bat wing, whale flipper).
Question
Define analogous structures.
Answer
Structures with a **similar function but a different basic plan** and no recent shared ancestor for that feature (e.g. bird wing vs insect wing).
Question
What is divergent evolution?
Answer
One ancestral form gives rise to **several different forms** — it produces **homologous** structures.
Question
What is convergent evolution?
Answer
Unrelated species under similar conditions evolve **similar features independently** — it produces **analogous** structures.
Question
Which is the strongest evidence for evolution?
Answer
**DNA / base-sequence comparison** — more shared sequence means more closely related species.
Question
List the main lines of evidence for evolution.
Answer
**Homologous structures, fossils, biogeography, selective breeding and DNA base sequences.**
Question
Homologous structures are evidence of which evolution type?
Answer
**Divergent** evolution — one common ancestor, then modified for different jobs.
Question
Analogous structures are evidence of which evolution type?
Answer
**Convergent** evolution — similar features evolved separately under the same selection pressure.
Question
Why is selective breeding evidence for evolution?
Answer
It shows that **heritable characteristics of a population can change** quickly when there is selection — here, by humans.
Question
Why is Lamarckism NOT valid evidence for evolution?
Answer
Traits **gained during an organism's life are not heritable**, so they cannot be passed on; evolution acts only on heritable variation.
Question
How do you tell homologous from analogous structures?
Answer
Homologous = **same plan, different job** (common ancestor); analogous = **same job, different plan** (convergent).
Question
Why does DNA evidence strengthen the case from body plans?
Answer
DNA is an **independent** clue — when a DNA cladogram agrees with one built from anatomy, two separate lines of evidence point to the same ancestry.
Question
On a cladogram, how do you find a species' closest relative?
Answer
Trace both branches **back to the node where they meet**; the pair that join at the **most recent (lowest) node** share a common ancestor most recently, so they are the **most closely related**.
Question
What does a node (branch point) on a cladogram represent?
Answer
The **most recent common ancestor** of all the species above that point.
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Topic 1.8 hub
Evolution and speciation
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