homologous and analogous traits
A horse's front leg and a human arm are examples of homologous structures. They have the same number and arrangement of bones meaning they probably evolved from a single type of structure present in a common ancestor. Humans are members of the Primates and horses are members of the perissodactyla. Both orders are part of the subclass Eutheria. A horse's front leg and a human arm both contain the humerus, radius, ulna, carpels, metacarpels, and phalanges. In a human, both the bones and muscles work in coordination with each other to makes various functions of the human hand possible. However, in a horse's front leg each bone is connected allowing the horse to lift, bend, and flex it's legs for movements such as running and jumping.
Two examples of analogous species are the whale and the lizard. They have similar skeleton structures but they have different habitats and lifestyles. Whales use their fins to swim and lizards use their legs to climb. Each of them are similar in structure but different in detail. Mosasaur fossils are always found in association with fossils of known marine origin. Whales are known to be descendants of land mammals via several physical characteristics: bones in their flippers which resemble the forelimbs of land mammals, vertical movement of their spines which resembles a running terrestrial animal, and the fact that they must breathe air. Both belond to the class of Mammals.
Good job on the homologous trait. Great background and description.
ReplyDeleteYour example of an analogous trait is actually homologous, believe it or not, though it was a little difficult to tell which trait you were talking about. I think you were doing limbs?
Whales are mammals. Their limbs are distinctly different from non-marine mammals, but genetically, they arose from a common mammalian ancestor. Well, where did the mammals inherit their limb structure? From early reptiles, like the ancestors of the lizards you mentioned. So the limbs of whales and lizards look very different but originate from a common ancestry, which is the definition of homology.
Analogous traits will have similarities in structure but without the common descent. And example would be the fins of whales and the fins of fish. Whales developed their fins independently.
okay that makes sense. I was a little bit confused when I was researching these animals and their traits. But thank you for your input it was very helpful. I have a better understanding of the differences between the two now. Thank you!
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