Week 3: Analogy Homology
Homology
1-a
Species
possessing the homologous trait: human and dolphin
In biology, humans are classified as hominoids.
Specifically, it is a member of the primate family hominidae. From the
perspective of anthropology, human is defined as a creature that can use
language, which has complex social organization and technological development.
Dolphins (scientific name: Delphinidae) have typical
morphological traits of the toothed whale. Dolphins are aquatic mammals closely
related to whales and porpoises, which evolved about 10 million years ago in
the Miocene, which are widely found in shallow seas near continental shelves
and occasionally in fresh water. It mainly feeds on fish and mollusks.
1-b
The homologous trait shared by human and dolphin shall be
the similar bone structure of dolphin's forelimb and human arm & hand. More
specifically, small bones contained in fins of dolphins look like wrist and
finger bones in human hands (see Pic below).
1-c
The
common ancestor of human and dolphin might be terrestrial ancestor.
1-d
2-a
Species possessing the analogous trait: butterfly and sparrow
Butterflies
are classified as Lepidoptera,
and there are thousands of species in the world that fall under this category. The
shape of the butterfly is mostly between 5 and 10 cm. The body is divided into
the head, chest and abdomen; two pairs of wings; three pairs of feet.
Sparrows
generally have brown and black plaques on the upper body. Sparrows mainly
inhabit in human living environment, no matter in mountain, plain, hill,
grassland, swamp and farmland, or in towns and villages.
2- b
Butterfly and sparrow both have wings
concerning structure. In terms of the function, their wings help them fly in the
sky to escape from predators and adapt to the environment, as well as other
aspects. More specifically, butterfly has a pair of wings, which are mostly made
up of membranes and scales. Sparrow also has a pair of wings with internal bone
structure and external feather.
2-c
The common ancestors of butterfly and
sparrow indeed possess the analogous trait. According to the relevant research,
it is found that the ancestor of butterfly is caddis, and Archaeopteryx for sparrow. They both share the analogous
trait.
3-d
Hello Ninuo,
回复删除I too did the dolphin and human comparison. I was really surprised that our arms are similar to a dolphins flipper. I didn't really think about it. I just figured that we were homo -sapiens and had our own unique bone structure, who would have thought that we have similar traits as animals that live in water being that we live on land. Great work!
Hi Ninuo!
回复删除Very well done on the comparisons. I actually was researching about the dolphin vs. human contrast , and it was really interesting to read your post. I liked the picture that you used for that comparison, because it helped put your explanation into graphics, which personally made it easier for me to understand what you were trying to say. Same goes for your analogous trait comparison. Very well done!
Unknown,
删除I cannot grant credit unless I know who you are. I'm going to hope that you notice that you didn't earn credit for this comment (it will be noted in your gradebook) and that you email me to let me know who you are.
Laurie Rodriguez
"In biology, humans are classified as hominoids."
回复删除Well, we are part of a group called hominoids, which includes humans, ancestral humans but also all other apes. I'm not sure that is what you meant to communicate here, however?
"human is defined as a creature that can use language"
No. Humans can use AND create language. Many organisms can use language. It is the creation of language that is unique.
Can you describe humans from physical perspective? This assignment is about physical traits, so it might have been more helpful to describe our species based upon physical/environmental characteristics, like did for the dolphins.
You correctly identify a homologous trait in the next section (b) but you don't explain it. Can you describe how each trait functions and how these different functions (because they do function differently, correct?) are reflected in their differences in skeletal structures? These structural differences are clearly visible in your images, but they needed to be explained to your readers.
"The common ancestor of human and dolphin might be terrestrial ancestor. "
Why? And did that ancestor possess this trait? And how does this confirm that these traits are homologous?
Both humans and dolphins are mammals, so we know that the common ancestor would be an archaic mammal. We also know from the fossil record that early mammals possessed that generalized mammalian forelimb structure and passed that onto these two descendant species, with changes concurring over time due to differences in the environment (aquatic vs. terrestrial). That is what we need to know to confirm common genetic origin and confirm homology.
Good images.
Analogy: Good opening description of your species and good description of the commonalities in function that are reflected in the similar structures.
"The common ancestors of butterfly and sparrow indeed possess the analogous trait. "
How do you know? And wouldn't that mean that these traits are actually homologous since they arose from common genetic descent? Remember that analogous traits arise from independent evolution, not via inheritance from a common ancestor.
So how do we use ancestry to provide evidence that these traits are analogous?
It is difficult to guess at what the common ancestor of the bird and butterfly looked like some 100's of millions of years ago... it may have possessed wings or it may not have, but fortunately, we don't need to know that to confirm that these traits are analogous. While it is possible that the butterfly inherited its wings from that common ancestor, what about the bird? We know quite a bit about bird and bird-wing evolution. Birds evolved wings as they split from reptiles, and this occurred long, long after the split with that common ancestor with the butterfly. This means bird wing evolution occurred independently from that common ancestor with the butterfly. That is sufficient to confirm that these are not the product of common descent and are indeed analogous.
Good images.