Question

what can we learn about vertebrate evolution from tiktaalik that we did not know before?
how vertebrates evolved tetrapod limbs
how vertebrates evolved gills
how vertebrates evolved lungs
how vertebrates evolved vertebrae
how vertebrates evolved jaws

Explanation:

Tiktaalik is a fossil that is significant in understanding vertebrate evolution. Tetrapod limbs are an important feature in the transition of vertebrates from water to land. Tiktalik had features that were intermediate between fish and tetrapods, providing insights into how tetrapod limbs evolved. Gills were already known to be present in fish - like ancestors. Lungs had some prior understanding in the context of lungfish etc. Vertebrae were a more basic vertebrate feature with some prior knowledge. Jaws also had some understanding from earlier vertebrate fossils.

Answer:

how vertebrates evolved tetrapod limbs