1. Homologous Traits
a. The two different species that posses the homologous trait are the frog and lizard forelimb.
b. Homologous organs are those, which have the same basic structure, but different functions. An examination of the forelimb skeleton in different groups of land vertebrates reveals that the number and arrangement of bones remains the same. However, the forelimbs are used for diverse functions in different groups. In frogs, forelimbs are not generally used to locomotion or swimming. In a lizard, forelimbs are as prominently used for locomotion as the hind limbs.
c. The common ancestors of these two species are tetrapods. Tetrapods are the group of vertebrates with four legs. They occupy a wide variety of environments, and use their limbs for many differing functions. Tetrapods include the amphibians, reptiles, birds, mammals, and various extinct groups. Tetrapods evolved from lobe-finned fish during the late Devonian Period.
Frog forelimb
Lizard forelimb2. Analogous Traits
a. Bees and hummingbirds are the two different species that possess the analogous trait.
b. A hummingbird has no sense of smell because a hummingbird can rotate its wings in a circle, they are the only bird that can fly forwards, backwards, up, down, sideways, and hover in midair. Bees have two pairs of wings in addition to six legs, two antennas, and numerous mouth parts, each pair of which derives from different segments.
c. The wings of birds are homologous to the forelegs of 4-legged animals. But arthropods (including insects, crustaceans, etc.) have a totally different body plan from vertebrates, having diverged in evolution way back in the early Cambrian.
Bee
Hummingbird
"gatewaysocial",
ReplyDeleteYour analogous perspective between hummingbirds and bees was very interesting. I never actually saw the similarities between the two until I read your post. They do prove to be very similar in the sense of pollination and body structure, but are not related. This may have been one of the best analogous comparisons that I have seen yet.
Good Job!
-Trope
First, great discussion on the evolutionary origins of the forelimb of birds and insects. Beautifully clear explanation.
ReplyDeleteOne caution: When you talk about "tetrapods", keep in mind that we are tetrapods. So you can't really say that tetrapods are the ancestors of frogs and lizards. Frogs and lizards ARE tetrapods. But you can talk about how the forelimbs of frogs and lizards had a common origin in the evolution of early tetrapods, during the rise of amphibians. Does that distinction make sense?