Fossils of lobe-finned fishes, which are ancestors of amphibians, are found in rocks that are at least 380 million years old. Fossils of the oldest amphibian-like vertebrate animals with true legs and lungs are found in rocks that are approximately 363 million years old.
Three samples of rocks are available that might contain fossils of a transitional species between lobe-finned fishes and amphibians: one rock sample that is 350 million years old, one that is 370 million years old, and one that is 390 million years old.

Question

Fossils of lobe-finned fishes, which are ancestors of amphibians, are found in rocks that are at least 380 million years old. Fossils of the oldest amphibian-like vertebrate animals with true legs and lungs are found in rocks that are approximately 363 million years old.
Three samples of rocks are available that might contain fossils of a transitional species between lobe-finned fishes and amphibians: one rock sample that is 350 million years old, one that is 370 million years old, and one that is 390 million years old.

preetha · Answer

(a) Select the most appropriate sample of rocks in which to search for a transitional species between lobe-finned fishes and amphibians. Justify your selection.
(b) Describe TWO pieces of evidence provided by fossils of a transitional species that would support a hypothesis that amphibians evolved from lobe-finned fishes.

preetha · Answer

Whew, what do you think of that question?  How does one go about answering that?

anonymous · Answer

Are you really confused about this?

anonymous · Answer

Or is this a test? Lol

preetha · Answer

Well, I posted the practice test question.  Would like to encourage some explanations.

miracrown · Answer

@Preetha
 I can explain this. :) 

For (A): The transitional species must have existed in a time between 380 and 362 years ago. Which fossil would you choose? I would choose 370 since its the best choice... because that fossil existed before the 380 fossil. But after the 363 fossil, so it is intermediate. I choose the fossil that whose age was between 380 and 363 million years because that is the time period when the intermediate species must have existed. 

Oh wait, actually it came about after the 380 lobe finned and before the 363 amphibian like vertebrate... :O

miracrown · Answer

For (B): We need pieces of evidence that provide us with information about characteristics of amphibians. An intermediate species could have had lungs but not true legs, do you see what I mean? 

Think about things that are present of amphibians. What structure is characteristic of a frog? (things that will remain in the fossil) I would use bones from the feet and hands of the fossil as evidence also look at the hip bone of a frog it is characteristics of amphibians and it is different from fishes, so...the two pieces of evidence that I would look at are: feet/hands bones and hip bones. 


So, basically the lobe-finned fishes lived in the water only. So somewhere in between they started to be able to live in and out of the water... So those fossils in between should start to show more limb-like features. Also, they should show some sort of a lung/swim bladder So, their fins would be more paired and look more like legs/arms... As in front and back legs and they would have lungs/swim bladder as well as gills to support both the water and land environment... So something for walking evolving and something for breathing air evolving.


look at the bone/limb structure... So the intermediate species would have some of both... the limbs would be capable of swimming and almost ready for walking on land like amphibians.. But I think the other piece of evidence would be more developed lungs for breathing on land because really the limb structure is just one piece of evidence and the lungs would be the other.