Pleas answer the questions above. Thank you. Question 1 (6 points): We\'ve discu
ID: 148684 • Letter: P
Question
Pleas answer the questions above. Thank you.
Question 1 (6 points): We've discussed in class two hypotheses about the relationships of whales and artiodactyls. A fossil with what kinds of characteristics would support the placement of whales as show in the phylogeny on the right? Include the kinds of characteristics that are necessary and sufficient for the specific placement of whales. Explain why each kind of characteristic is important to support this phylogeny. Perissodactyls horses and rhinos) ARTIODACTYLS Camel -Peccary Gain of pulley- shaped astragalus Pig Hippo Whale Loss of pulley shaped astragalus Deer cowExplanation / Answer
Q1. All ungulate artiodactyls (even-toed ungulates) have pulley-shaped articulating surfaces on both ends of the astragalus (fossil evidence of cetaceans indicates that primitive whales also possessed this feature). This pulley shapes articulating surface is currently lost in whales and dolphins. But their presence in the old fossils of cetaceans (whlaes ancestor) should be considered for placing the cetaceans under ungulates (artiodactyls).
Q2. Homology refers to biological structures or characteristics that are similar found in two or more different species, which is the result of divergent evolution (inherited from a common ancestor). An example of homology is seen in the forelimbs of frogs, birds, rabbits and lizards. Although these limbs have a different appearance in each species, they all share the same set of bones.
Homoplasy refers to the biological structure or characteristic that two or more different species have in common but that was not inherited from a common ancestor. A homoplasy evolves independently (convergent evolution). For example: wings of butterfly and wings of bats, they perform the same function, but structurally they are different and are not eveolved from a common ancestor.
From the phylogenetic data, Monotremes are the recent ancestors of therians.
It is believed that monotreme and therian ancestors evolved very similar middle ear bones, but in two separate paths. In therians, the mandibular trough no longer held the quadrate, angular, and articular. These bones were held to the jaw by ossified Meckel’s cartilage. This bridge of cartilage and bone extended away from the dentary and approached the area that would make up the modern ear cavity. While in monotreme ancestors, there is a mandibular trough, that is believed to have accommodated the postdentary rod. This rod is believed to have been connected to the trough by ligaments. This rod was used for hearing and the quadrate, angular, and articular were no longer needed in the jaw hinge.
Hence the path of evolution is homoplasy in this case.