Question

Final tomorrow, help please!
Are animal appendages homologous? How do we know?

Answer 1

I think so. Common ancestor. They all look "alike" just different forms.

Answer 2

Depends. If you're talking about appendages on the same animal (ie all the legs on a cat) then each of those appendages will be, in a sense, homologous to each other as they are on the same organism.

If your talking about appendage comparisons BETWEEN DIFFERENT organisms, then it depends on their ancestry.

Appendages on two different animals that look alike and have the same function will be Homologous if the two animals share a common ancestor. Meaning that they got that trait from their ancestor, it's just been modified slightly through evolution. E.g. The hands of a monkey and the hands of a human.

Appendages on two different animals that look alike and have the same function will be Analogous if the animals DO NOT share a common ancestor with a similar appendage.
E.g. The body shape of a shark and a dolphin. This similarity is due to convergent evolution (evolution toward greater similarity due to SIMILAR SELECTION PRESSURES). The dolphin and the shark do not share a common ancestor.

Answer 3

Great answer, thank you! Helped a lot. (:

Answer 4

No problem. Good luck! :)