A student reads that the embryos of a fish, a frog, a chick and a human each have a row of slits on…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
A student reads that the embryos of a fish, a frog, a chick and a human each have a row of slits on both sides of the neck. She then writes four statements.
- The slits become gills only in the fish.
- The slits prove that a human embryo first becomes a fish and then a frog.
- The slits point to a common ancestor of the vertebrates.
- Von Baer showed that embryos pass through the adult stages of other animals.
Say which are true, and correct the false ones.
Need a reminder? The key ideaShow
Homologous organs have the same origin and different jobs (divergent evolution). Analogous organs have the same job and different origins (convergent evolution). Deeper rock layers are older. Radioactive carbon halves every years, so after half-lives is left.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. (a) True. The slits are gills in fish. In the other groups they do not form gills.
Step 2. (b) False. The embryo shares an early feature with a fish embryo. It does not pass through an adult fish or an adult frog.
Step 3. (c) True. A shared early feature points to a common ancestor.
Step 4. (d) False. Von Baer showed the opposite. Embryos never pass through the adult stages of other animals.
Answer: (a) and (c) are true. (b) and (d) are false.
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