Week 3 - Analogy & Homology Blog Post
1. For your homologus traits provide the following information (25pts):
a. Briefly describe the two
different species that possess the homologus trait. (5 pts)
Humans
and Cats both carry a homologous trait of possessing phalange bones.
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)
Human
phalanges are located in a person’s two hands and two feet. They are most
commonly known as fingers and toes. Fingers are used for an infinite number of
things varying from typing, to pushing buttons, to pinching, etc. Toes are a
vital body part that assists a person by providing balance.
Cat
phalanges are located in all four cat’s paws. They are most commonly known as
toes. A cat’s two front paws have five toes while the two back paws have only
four toes. Toes, like in humans, provide a balance assist a cat with balance along with grip and support (i.e. when they climb).
So, while
the phalange bones in a human are essential for balance (toes) and manipulating
other objects (fingers), the phalange bone in a cat is solely essential for
balance (toes).
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)
Boreoeutherian
is the common ancestor between cats and humans.
d. Provide an image of each species
in this comparison. (5 pts)
2. For your analogous traits provide the following information (25pts):
a. Briefly describe the two
different species that possess the analogous trait. (5 pts)
Flies
and birds have wings as an analogous trait.
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)
Flies
have a pair of fully developed wings on the thorax and a second pair of wings that
are used primarily for balance.
The main
function of a bird wing is to propel the animal in flight so it can travel to
wherever necessary and also provides warmth and protection for their offspring.
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)
Coelurosaurian
theropods is the common ancestor of flies ad birds.
d. Provide an image of each species
in this comparison.(5 pts)
Bird Wing
Fly Wing
It's weird that even though both cats and humans have phalanges, we use our fingers and toes for so much more than cats. The cat's phalanges are just slightly more bent than ours to act as paws. It's also strange to think that our small toes are what's keeping us from toppling over.
ReplyDeleteIn general, good discussion and comparison between the human and cat phalanges. While Boreoeutherian may indeed be a candidate for a common ancestor, the specific organism wasn't crucial here. In order for these to be homologs, they need to be the result of common ancestry. How do you know the common ancestor possessed the ancestral version of this trait and passed it on to humans and cats?
ReplyDeleteOkay on your analogous description but again you are missing the key point on the issue of ancestry. It matters less as to whom the specific ancestor was and more that you understand if the common ancestor passed on the trait in question to these two organisms. In order for these traits to be analogous, the trait had to have arisen independently in at least one of these organisms. What do we know about bird wing evolution that can help us confirm that these traits are analogs?