10. Why is a sturdy ribcage important for tetrapods?

11. What is homology? To what are fins homologous?

12. Why are lobe - finned fish thought to be the closest relatives to tetrapods?

The bone structure is the main reason.

Explanation:

The reason why is important to have a sturdy ribcage is to maintain important organs like heart and lungs secure to impacts or physical shocks. Homology is observed when certain organs are related based on ancestry of different species, for example there is homology on fins and arms of all tetrapods because fish and tetrapods had in past a common ancestor. Therefore, the idea of close relatedness between those kind of species is based on the bone structure that is shared on them.