Essay on Dinosaurs: Hair and Humans

Differences in size affect many biological aspects of life within species. Through the processes of evolution and natural selection, species have evolved today to meet their biological needs. The two species that I chose to compare were a porcupine and a human being. Although the two species are of the same class, mammalia, they have obvious biological differences that affect their way of life.
The first feature that I chose to compare is the biomaterial made of protein, also known as hair. The hair of a porcupine comes in the form of sharp quills. These quills protect the porcupine from predators and other dangerous threats. They also serve to camouflage the animal so that they can hide from predators. In addition to camouflage, the small size of porcupines (12-35 pounds) makes them more inconspicuous and away from danger. The interesting aspect about their quills is that they are merely modified hairs, similar to the hair found on humans. However, the hair on porcupines is coated with thick plates of keratin, which make them extremely sharp. These quills release by contact, which can be very dangerous to a predator. When the quills are removed, new quills grow in place, which is similar to the process of regrowth of human hairs.
In humans, the physiological feature of hair serves a different purpose. The major role of hair on humans is warmth. When the body is cold, the arrector pili muscles that are attached to hair follicles stand up, along with the follicles. These hairs then form a heat-trapping layer above the epidermis. The opposite can also occur when the body needs to be cooled, the arrector muscles allow the hair to lie flat; which allow heat to leave. Although human hair may not compete with the painful quills of a porcupine, body hair on humans do serve an important role for protection. For example, eyebrows and eyelashes protect the eyes from dirt, dust, sweat, and rain. Although this natural armor on humans cannot directly protect them from potential predators, it helps keep the sense organs working properly.
The second feature between humans and porcupines are hands and feet. Porcupines have small, four-fingered hands with long, curved claws and five-fingered toes with long, curved claws. This anatomy most likely developed to allow porcupines to climb trees. These animals are nocturnal and will hide in trees during the day and find food at night. Their hands and feet allow them to quickly climb up trees and out of the danger. Also, porcupines are quadrupedal and use all four limbs for moving. This is an important anatomical feature because porcupines are small and would lose against a fight with a predator of larger size. Porcupine’s best defense mechanism is to run, and their curved hands and feet allow them to efficiently escalade trees.
As opposed to claws, humans have two hands, each with five digits. The hands and fingers allow for various motor skills essential to everyday life. A human also has two feet

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