Analogy/Homology
a. Briefly describe the two different species that possess the homologus trait.
The skeletal structures of the forelimbs of a bat, and a mouse, exhibit a homologous trait. They both
developed similar traits from their tetrapod ancestors.
b. Describe the homologous trait of each species, focusing on the differences in structure and
function of the trait. Why do these homologous traits exhibit differences between the two
species? Make sure your explanation is clear and complete.
Both bat forelimbs and mouse forelimbs consist of a stylopod, zeugopod, and autopod, which actually look quite similar to a human’s forelimbs (humans, bats, and mice are al mammals, so it makes sense). One major difference in a bat’s forearm is that its’ skeletal limb structure is elongated. Another major difference is the density of a bat’s skeletal limbs. Their bones are especially light, which is necessary for flight. Homologous evolution leaves room for mutation. Through generations of natural selection and evolution, these species’ homologous trait evolved to better suit each individual species.
c. Who was (generally, not specifically) the common ancestor of these two species and how do
you know that ancestor possessed this homologus trait?
The common ancestor of these two species is the ancient tetrapod. Tetrapod’s are vertebrate animals having four limbs. We know that tetrapods are the ancestor of both the mouse and the bat because of the similarities in the evolution, and structures of the mammals, and tetrapods.
d. Provide an image of each species in this comparison.
a. Briefly describe the two different species that possess the analogous trait.
Limpets and barnacles have several superficial qualities that are similar. Both can be found in the ocean on rocky shores, and both are small creatures with cone shaped shells. They may look very similar, but the structures of these species are very different. They innards are very different.
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.
The analogous trait exhibited here would be the outer shell. Both species have a hard outer shell. Barnacles innards, however, are more similar to a shrimp; even containing small legs. Limpets bodies, on the other hand, resemble a snail’s body. They both faced similar challenges: rocky environments constantly being eroded by waves, and teeming with predators ready to pry small prey off of the rocks for lunch. The cone shaped armor made it hard for predators to penetrate. These lineages shells evolved independently of eachother.
c. All pairs of organisms share some common ancestor if you go back far enough in time. Did
the common ancestor of these two species possess this analogous trait? Why or why not?
The ancestor of these species would be the bilateria, a worm-like common ancestor. Bilateria, however, have no shell. They didn’t need a shell for survival in their natural environment, the way that limpets and barnacles do.
d. Provide an image of each species in this comparison.
Limpets Barnacles
