1. For your homologus traits provide the following
information (25 pts): a. Briefly describe the two different species that
possess the homologus trait. (5 pts)
Dog, a mammal (and a pet) with four feet. Dolphine, also a mammal, but lives in the
water.
b. Describe the homologus trait of each species, focusing on
the differences in structure and function of the trait. Why do these homologus
traits exhibit differences between the two species? Make sure your explanation
is clear and complete. (10 pts)
Legs of a dog and the flippers of the dolphin. The dolphin was once known as terrestrial and
they became aquatic and lost their legs so they could utilize new
resources.
c. Who was (generally, not specifically) the common ancestor
of these two species and how do you know that ancestor possessed this homologus
trait? (5 pts)
They both evolved from mesonychidae. They are known to have lived in land. About 30 million years ago, some of them
began to adapt to the ocean life and developed useful traits to live in the
ocean.
d. Provide an image of each species in this comparison. (5
pts)
2. For your analogous traits provide the following
information (25 pts):
a. Briefly describe the two different species that possess
the analogous trait. (5 pts)
Penguins that live mostly in land, and fish that live
exclusively in the water
b. Describe the analogous trait of each species, focusing on
the similarities in structure and function of the trait. Clearly explain why
these analogous traits exhibit similarities between the two species. (10 pts)
Fins of penguins and fins of the fish
c. All pairs of organisms share some common ancestor if you
go back far enough in time. Could the common ancestor of these two species have
possessed this analogous trait? How do we know these traits are analogous and
not genetically related from common descent? (5 pts)
The common ancestor could have some similar trait, but the ancestor
probably did not have the same ones. They
are analogous because the fin was best functional feature for each species’s environment
even though they come from very distant common ancestors.
d. Provide an image of each species in this comparison. (5
pts)
I usually caution students away from using domesticated animals (like dogs) as they have been shaped by artificial selection as much as natural selection. However you are comparing limb structure which developed well before humans came on the scene, so this should work.
ReplyDeleteA little short on your opening description of your species? Expand.
The limbs for the dog and dolphin are actually quite complex. Are you focusing on specific bone structures or the overall shape? What specific similarities are you highlighting and what functional differences between the two? Again, expand.
Mesonychidae is thought to be one of the earlier mammals, but we didn't need to get that specific. Both dogs and dolphins are mammals, so they arose from an archaic mammal who possessed the early mammalian limb structure and passed it on to these two descendants. That explains the similarities in structure via common descent.
Cute image of the dog. The other image is actually of a beluga whale, instead of a dolphin.
Expand opening explanation of your analogous pairing.
The section where you were to identify similarities in structure and function and explain the selection pressures that produced them is insufficient for full credit.
If the common ancestor possessed the trait, would these be analogous traits?
The question is, did the trait in question arise from that common ancestor or did it evolve independently in at least one of the organisms? In this case, the common ancestor was a fish, so it is likely that the modern fish did inherit its fin structure from that common ancestor. But did the penguin? The penguin is a bird and the "fin" is an evolved bird wing. We know that wings didn't evolve until birds split off from their reptilian ancestor, long after the split with the common ancestor of the fish. This is what we need to confirm that the penguin "fin" arose independently from the common ancestor with the fish and therefore these traits are analogous.
Good final images.