Untitled Quiz

Study Notes

Homologous structures arise when two organisms inherit traits from a common ancestor.
Example: The limbs of mammals share common bone structures despite differing functions, indicating a shared ancestry.
Notable examples include:
- Leaves of oak and ginkgo trees: Both share leaf traits inherited from a common ancestor.
- Wings of butterflies and dragonflies: Inherit from an ancient flying insect.
- Beaver and elephant incisor teeth: Both share homologous dental structures.

Analogous structures result from convergent evolution, where organisms develop similar traits independently due to similar environmental pressures.
These features do not indicate a shared ancestry.
Example: The eyes of different species may evolve similarly to adapt to similar light conditions but do not share a common ancestor.

Both homologous and analogous structures involve organisms gaining traits.
Homologies involve shared traits from ancestors; analogies involve similar traits arising independently.
Homologies are about inherited structural traits, while analogies focus on functional similarities due to evolutionary adaptation.

Criteria for determining dissimilarity in structures include bone composition and overall architecture.
The forelimbs of tetrapods are structurally diverse but serve functions such as grabbing and catching, highlighting functional variability despite structural similarities.

The grasshopper leg and lizard leg are not homologous due to differing bone structures, indicated on a phylogenetic tree.
The saber teeth of Thylacosmilus and Smilodon are analogous; they appear similar but diverged significantly on the evolutionary timeline, reflecting their different species origins.

Analogies develop when traits prove advantageous for survival under similar environmental challenges, resulting in adaptive similarities across species facing analogous problems.