Analogy/ Homology

1.      Homologous Trait Information:

A)    The two different species that possess the homologous trait of having scales are the American alligator and the American crocodile. The American alligator is a reptile that is part of the alligatoridae family of crocodilians. They live in freshwater lakes, marshes, swamps, and rivers. They have a round snout, a low lying body, and a body armor that consists of thick keeled scales that are large, dark, and green and grey in color. The scales, although tough, are also smooth and don’t have ridges. The American crocodile is a reptile that is part of the crocodylidae family of crocodilians. They are lighter in color and have a thinner, pointier snout than the American alligator. Their scales are more brown and grey in color and they also have rows of raised scales. They live in coastal lagoons, fresh water river estuaries, and mangrove swamps.

B)    The homologous trait of each species is having scales on their skin as a means of protection. American alligators use their scales as not only a means of protection from predators, but as a means of protection from the environment as well. Since they are low lying to the ground, their scales act as a barrier and help protect them from the roughness of the ground. American crocodiles use their scales to protect their internal organs from harm during fights with predators. They also use the size of their scales as a way to swim faster and more efficiently since the scales gives their tails a larger surface area. These traits exhibit differences in between the two species because of the species have adapted the use of their trait to their environment. For instance, a salt water crocodile will use their scales more for the protection from the salt water environment they live in where as an alligator living in a swamp that is highly populated by other alligators will use their scales more for protection from rival alligators.

C)    A common ancestor of these two species was the dinosaur. I know that the ancestor possessed this homologous trait because scientists have discovered fossils which have shown detailed imprints of the different sized scales found on their bodies. Having scales also protected them from even larger predators.

D)    The following are pictures of an American crocodile and an American alligator.

 

2. Analogous Trait Information:  

A)Two different species that possess the same analogous trait of releasing chemicals as a defense    mechanism are the octopus and the skunk. Skunks are small striped mammals that average the size of a common housecat. They have anal glands that are used for defensive purposes when they feel that predators are around. When they sense a predator or feel like they are in danger, their defense is to turn around and spray a horrible smelling oily liquid in the predator’s face. Although not toxic, this spray is enough to send them running. Octopuses are invertebrates which have no internal skeleton. They have several defenses when it comes to warding off predators which include camouflage, hiding, and inking. When they feel they are in danger and that a predator is near, they release a large cloud of black ink which allows them to escape. Although not fatal, it s thought that the ink might lessen the efficiency of ones sense of smell.

B)   The analogous trait that each species has is the ability to release chemicals as part of their defense mechanism. Both of these animals release a specific liquid chemical that will hopefully allow them to stun their prey and let them escape unharmed. The octopus releases a cloud of ink to block the view of its prey and the skunk releases a smelly oily liquid which will affects its prey’s smell and make it difficult for them to track them.

     

C)    Unfortunately, I could not find a common ancestor for these two species and therefore am not aware if one possesses the same analogous trait that they do.

D)    The following are pictures of a skunk and an octopus