Homologous structures are physical features in different organisms that share a common ancestor but may have different functions. These structures have similar underlying anatomy or genetic origins due to descent from the same ancestor, even though their current uses may vary, such as the forelimbs of humans, dogs, birds, and whales, which have different functions but similar bone structures. They arise from divergent evolution, indicating evolutionary relationships among species.
Key Characteristics of Homologous Structures
- They have similar anatomical composition or DNA sequences due to common ancestry.
- They may serve different functions in different organisms (e.g., human arm for grasping, bird wing for flying).
- They illustrate evolutionary descent and divergence from a common ancestor.
Examples
- Limbs of humans, cats, whales, and bats.
- Forelimbs of vertebrates such as arms, legs, wings, and flippers.
- Genetic homology seen in DNA or protein sequences shared among related species.
Comparison with Analogous Structures
- Analogous structures have similar functions but arise independently and do not share a common ancestor.
- Homologous structures show similarity in form or genetic origin but may have different functions.
In summary, homologous structures demonstrate evolutionary inheritance from a shared ancestor, showcasing structural similarities regardless of functional differences.