Homologous Traits
Koalas
and kangaroos each are two different species that possess a pouch for their
precocious young.
The
pouches of each species are used for keeping their premature offspring for
further development beyond the womb. The kangaroo’s pouch differs from koala
pouches in that kangaroo pouches open horizontally on the front of the body,
while a koala’s pouch opens backwards and down, it also has a sphincter that
keeps the young from falling out. Both of the species pouches are sticky,
however, the kangaroo will lick their pouch clean, unlike koala pouches which
have a self-cleaning system. The differences in the pouches between the two
species developed due to the differences in environment and lifestyles. The
koala’s pouch would not work well for kangaroo because the young would fall out
very easily, and the front horizontal pouch would not work well for koalas since
they climb trees and the young would also fall out.
The
earliest known common ancestor of kangaroos and koalas has been identified as Hypsiprymnodon bartholomaii. Not much is known about marsupial ancestors,
but it is believed that the evolution of their pouches evolved due to
competition with placental mammals.
Analogous Traits
Dolphins
and goldfish both possess a dorsal fin. A dorsal fin is a fin located on the
backs of marine and freshwater animals.
In
each species the fin is used to help navigate through water. The fin stabilizes
the body and keeps it from rolling over in water. The dorsal fin also assists
in sudden turns. Each species developed fins as an adaptation to living in
water environments.
Going
back to 405 million years ago, sea mammals and fish evolved from a common
ancestor from the group Osteichthyes. Osteichthyes
did, and still possess fins.
I really enjoyed reading your post about the Koalas! I read that their pouches become almost translucent because it is so clean.
ReplyDeleteA must fee item is how a baby makes it's way from the birth canal, up and into the mother's pouch.
Thank you, Judith! I did not not know that about Koalas, but that's pretty interesting. The pouch even produces an antibacterial enzyme of some sort. The babies are so tiny but I am very curious to see one in person.
ReplyDeleteNIce post. I didn't even Koalas had a self cleaning system, and kangaroo's really lick their pouch? Gross. I wonder at what age is the Koalas too big to fit in the pouch anymore or even the kangaroo.
ReplyDeleteThey do! Unfortunately, my sources didn't say when the cut off date is but imagining a grown kangaroo still hanging out in one is pretty funny.
DeleteThat is really cool about koalas having a self-cleaning system for their pouch! I didnt know that prior to reading your post. Also your the last part is interesting on how the ancestor of the kangaroo and koala developed the pouch to compete with placental mammals.
ReplyDeleteGood background information on the koala and the kangaroo. It is really interesting how different means of mobility can influence the positioning and structure of the pouch. Do we have evidence that the common ancestor possessed a pouch? Do we know what the ancestral phenotype was (up, down, backward, etc.)?
ReplyDeleteGood choice on your analgous trait and good background. But here is the question: If the common ancestor (which you did a great job tracking) possessed a dorsal fin, doesn't that make this a homologous trait? Or are other factors involved here? Did both species inherit that trait from this common ancestor?
There wasn't too much information about for Australian Marsupial's common ancestors, just that it came from South America.
DeleteThe Dolphin and the goldfish share a common ancestor, like all animals do but the trait is not homologous. The ancient bony fish branched off into different species (simplifying, for the sake of brevity)that are cartilaginous fishes and bony fishes (pretty much remained the same) and into land mammals. The land mammals then evolved into water animals. The fin in a fish is not really similar to a fin in a dolphin in the sense that they did not evolve in the same way.
Very good examples! I didn't know that koalas had a pouch like kangaroos. I also didn't know that kangaroo's like their pouches clean. I really like the both examples you used for both.
ReplyDelete