Analogy/Homology

1.        

a.       Two different species that share a homologous trait are chickens (birds) and humans (mammals); more specifically their wings and arms, respectively. The skeletal structure of a wing from a chicken is built to rapidly flap causing the animal to briefly elevate off the ground for several seconds. Chickens cannot fully fly for long periods of time like other birds, but they can jump and fly for several seconds to cover some ground. Humans on the other hand cannot fly at all, nor can they flap their arms fast enough to elevate. A human’s arm is utilized to grab, build, maneuver and do complex things.

b.       The homologous trait between chickens and humans share differences of structure between wings and arms. Wings on a chicken are arranged so that they begin at the front part of the animal’s body, leading in a horizontal direction towards its rear extremity. Each of these wings have three main joints, and three fingers. Though these fingers are not as identifiable as they are on a human’s hand. Humans on the contrary have arms that extend from their upper body, hanging vertically adjacent to their torsos and move in various directions.  

       

c.       The common ancestor of chickens and humans is a vertebrate animal. Those considered vertebrates have a vertebral column and over time developed forelimbs, which are considered tetrapod. The forelimbs of chickens and humans is a clear example that the limbs (wings and arms) are homologous; meaning that they derive from a common ancestor.

d.     Skeletal image of a chicken wing and human arm.

2.        

a.       Two animals from different species that share an analogous trait are rabbits and kangaroos. Rabbits are mammals that live on dry land, with agility to move around. Kangaroos are marsupials that also live on land. Both these animals have similarities in appearance; fur, ears, four legs, and strength in hind legs.

b.       These two animals’ main analogous trait are their hind legs. The strength on their legs could help them bounce from different locations in a highly agile manner. This gives them the opportunity to evade predators and get to locations in a short amount of time. The structure of their hind legs is similar and much bigger in size compared to their front legs. Clearly, they utilize these powerful legs to catapult from one place to another in order to mobilize.

c.       We know that these are analogous traits because both animals are from different species. Rabbits are mammals and Kangaroos are marsupials, therefore they don’t share a genetically common ancestor. They both however are classified and branch from Chordata into Vertebrata and Mammalia.

d.       Image of a rabbit and kangaroo.

Historical Influences on Darwin

Jean-Baptiste Lamarck is most recognized today as the French scientist who proposed that “As organisms adapted to their surroundings, nature also drove them inexorably upward from simple forms to increasingly complex ones” (O’Neil). He suggested the strong relationship between environments and species stemmed from external environmental changes, which affects the animal’s pattern causing it to accommodate to its surroundings (Jurmain 30). One of his examples was the explanation of the neck lengths of giraffes. He believed that they evolved as generations of giraffes reached for higher leaves (O’Neil).

Lamarck’s suggestion goes in line with, “If the environment changes, the traits that are helpful or adaptive to that environment will be different”. In his explanation of the evolution of the giraffe, the environment change are represented by taller trees with higher leaves. The traits of generations of giraffes are in conjunction with longer necks that help these animal reach the higher leaves. It is a great example of adaptation to a changing environment.

As Charles Darwin began his college education at Edinburgh University, he became aware of Lamarck’s evolutionary theories (Jurmain 34). It is possible that Darwin could not have developed his theory of natural selection without the works of Lamarck. Darwin’s natural selection theory has a foundation in Lamarck’s environment and species adaptations. Furthermore, Darwin’s observation of the variations of finches found at Galapagos island is a near reflection of Lamarck’s explanation of the giraffe evolutionary changes. Both animals over generations have gone through evolutionary changes in order to adapt to their changing environment; the finches with different sized beaks and the giraffes with different sized necks. In turn, natural selection gives favor to the animal that is able to physically adapt to the changing environment in order to survive.

Charles Darwin was hesitant to publish his theory because he knew it would be highly controversial facing opposition from the church. Evolutionary theories were viewed as very serious threats (Jurmain 38). Soon enough – after seeing that he had competition from Alfred Russel Wallace – Darwin published Origins of Species on December 1959.

Online Reference

https://evolution.berkeley.edu/evolibrary/article/history_09

If you were stranded on a desert island what two items you would take with you and why?

My first item would be a weather proof tent, just big enough for an individual, and the second item must be a spear. Shelter and a hunting tool is all I need to survive in a deserted island. Staying safe from the natural elements and eating should bring forth survival.