Homology and Analogy

1. Homologous

Two different species that carry the same trait is a Humming Bird and an Eagle. Hummingbirds are birds that make up part of the Trochilidae family. They are among one of the smallest birds ranging from only 7.5-13cm long. The Eagle on the other hand is a much bigger and more powerful bird that belongs to the Accipitridae family. Their size starts at 40cm long and increases according to each certain species. The trait that Hummingbirds and Eagles share is the structure of their wings—they both possess the same skeletal structure in their wings. Their digits are stacked on one another to support their wings; in addition, they also have an ulna, radius, and humerus as a part of their skeletal structure. This homologous trait plays a different role in the lives of both hummingbirds and eagles. Hummingbirds’ skeletal structure allows for faster movements as they hold the ability to flap their wings 12-80 times per second. Not only can they fly fast (25 to 20 miles per hour), the wings of a hummingbird gives it the abilities to fly forward, backward, hover, and upside-down for a short amount of time. Hummingbirds do not flap their wings when they fly (only when they hover), they rotate it in an oval pattern thanks to the ball and socket joint in their shoulder.  As for the eagle, their skeletal structure is more hallow so that they have the ability to glide without the need to constantly move their wings (this provides the eagle with more velocity rather than wing speed). The shape and size of an eagle’s wings work with the air current to help the eagle keep its high altitude. In addition, eagles have wing slots which are finger like gaps between their large and primary feathers that help them with stability and maneuvering as they fly. The common ancestor for the hummingbirds and eagles can be traced as far back as the birds of the Jurassic period. These birds are categorized as Aves; both the Humming bird and the Eagle contain structures similar to the Jurassic Aves. 

2. Analogous

Two different species that posses an analogous trait are apes and pandas. Apes belong to the Hominoidea family and are considered Old World anthropoid mammals. They are native to Africa and countries in South-east Asia. Pandas on the other hand are native to only south central China, but there have been an increased effort to breed pandas (especially in zoos) in other locations such as North America and Europe. Their diet is 99% bamboo but when circumstances require it, they will eat meat. The trait both apes and pandas share is the possession of opposable thumbs. The skeletal structure of the both the ape and the pandas hands consist of similar bones that make up an opposable thumb. Pandas have six phalanges instead of five like an ape. The panda has five normal phalanges along with a “thumb” called a False Thumb. This thumb is the panda’s opposable thumb that makes it possible for pandas to hold bamboos to eat. . Pandas on the other hand come from the bear family. Pandas developed their “false thumb” due to the need to eat (and their specific diet of bamboo) to ensure survival. Because they mainly eat bamboo, it was significant and crucial that they developed opposable thumbs to grab the bamboo and break it off which increased their chances of survival. Taking a look back into the ancestry of apes tells us that they had always possessed opposable thumbs. This trait developed due to the environmental demands and the need to survive. Apes need their opposable thumbs to climb trees and grasp vines and braches so that they are able to swing from one tree to the next. This is their way of surviving and hiding from their preys on the grounds—their survival is dependent on the possession of opposable thumbs. Opposable thumbs developed in both apes and pandas to help them survive. Both use their opposable thumbs to extract food to decrease their risk of starvation; this trait gradually appeared in both animals due to harsh environmental conditions that threaten to kill those who do not adapt.