Evidence for Evolution — Flashcards & Quiz

Q1: What are homologous and analogous structures?

Homologous structures: similar underlying anatomy inherited from a common ancestor but adapted for different functions (divergent evolution). Evidence of common descent. Analogous structures: similar function but different evolutionary origin (convergent evolution). NOT evidence of common descent — they evolved independently in response to similar selection pressures.

Q2: What are vestigial structures and how do they provide evidence for evolution?

Vestigial structures are reduced or non-functional remnants of structures that were functional in ancestors. They provide evidence for evolution because they indicate descent from ancestors where these structures had a function. The structures have been retained but reduced through evolution because they no longer provide a selective advantage.

Q3: How does biogeography provide evidence for evolution?

Biogeography studies the geographic distribution of species. Evidence for evolution: 1) Island species are most similar to nearest mainland species, not to species on similar islands far away. 2) Continental drift explains why fossils of the same species are found on continents now separated by oceans. 3) Endemic species on isolated islands (evolved from colonising ancestors). 4) Similar environments on different continents have different species (convergent evolution, not special creation).

Q4: What are comparative embryology and its limitations as evidence for evolution?

Comparative embryology observes that embryos of related species show greater similarity in early development than in adult forms, reflecting shared developmental genes (e.g., pharyngeal arches in all vertebrate embryos). Evidence: common developmental pathways suggest common ancestry. Limitations: 1) Haeckel's original drawings were inaccurate (embryos are not as similar as he depicted). 2) Development can be modified by selection. 3) Similarity in early development may reflect conserved developmental genes rather than identical structures.

Q5: What is convergent evolution and how does it differ from divergent evolution?

Convergent evolution: unrelated species evolve similar traits independently in response to similar selection pressures. Produces analogous structures (similar function, different origin). Divergent evolution: related species evolve different traits from a common ancestor in response to different selection pressures. Produces homologous structures (similar structure, different function). Both are driven by natural selection but in different contexts.

Q1: Analogous structures provide evidence of common ancestry between two species.

Answer: FALSE

ANALOGOUS structures result from convergent evolution — similar function but different evolutionary origin. They do NOT indicate common ancestry. HOMOLOGOUS structures (same origin, different function) provide evidence of common ancestry.

Q2: Vestigial structures have no function whatsoever in the organisms that possess them.

Answer: FALSE

Vestigial structures are REDUCED from the ancestral condition and no longer perform their ORIGINAL function, but they may have acquired minor secondary functions. For example, the human appendix may play a small role in immune function.

Q3: Convergent evolution occurs when unrelated species develop similar traits in response to similar selection pressures.

Answer: TRUE

Convergent evolution produces similar adaptations in unrelated lineages facing similar environmental challenges. Examples include streamlined body shapes in dolphins (mammals) and sharks (fish), and camera eyes in vertebrates and octopuses (molluscs).