Question

answer the following questions in complete sentences. cite where your answers came from (pp/slide #, textbook page)

1. how are fossils helpful in identifying ancestral and derived traits of organisms? describe an example.
2. what is the problem with the classification shown below? how could genus a and/or genus b be modified so that both genera are monophyletic?

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Explanation:

Question 1

Fossils preserve the physical structures of ancient organisms. By comparing fossilized traits (like skeletal features) with modern organisms, we can identify ancestral traits (inherited from a common ancestor) and derived traits (newly evolved). For example, the fossil record of horses shows ancestral traits like multiple toes (seen in Eohippus fossils) and derived traits like a single hoof (in modern horses), helping trace evolutionary changes (source: Biology textbook, Chapter on Evolution, p. 234).

The problem is that the classification is paraphyletic. Genus A includes Species 1 - 3, but Species 4 (a close relative) is excluded. Genus B includes Species 5 - 7, but Species 4 (part of their clade) is in Genus A. To make them monophyletic, either move Species 4 to Genus B (so Genus B includes Species 4, 5, 6, 7, as they share a common ancestor) or redefine Genus A to include Species 4 (but Genus B would then need adjustment too; moving Species 4 to B is more logical, as Species 4 is more closely related to B’s species than A’s) (source: Biology textbook, Phylogenetics chapter, p. 198).

Answer:

Fossils help identify ancestral and derived traits by preserving ancient organisms’ physical structures, allowing comparison with modern forms. For example, horse fossils show ancestral multiple - toed limbs (e.g., Eohippus) and derived single - hoofed limbs (modern horses), revealing evolutionary trait changes (source: Biology textbook, Evolution chapter, p. 234).

Question 2