Some of the earliest teeth were first discovered in lamprey fish in what has become known as conodont fossils. Through the study of teeth, it has been determined that they develop as the result of an interaction between two tissue layers from which cell division, shape change, and protein production within the two layers brings the formation of a tooth. This process of formation by two layers of tissue was modified to build other organs including hair, feathers, and mammary glands. Using the themes of evolution and relationship between structure and function, explain how the different purposes of each of these organs relate to their similar structure.
Sami Kopinsky
sami_kopinsky@yahoo.com
Feathers are used in birds to regulate temperature, camouflage, fly, and for mating purposes. The structure of feathers is ideal for helping birds perform many necessary functions. For example, feathers are small and densely packed together, which helps keep birds warm. The down base of feathers traps an insulating layer which helps the birds retain heat(Cornell- Feathers and Plumages). The color and markings on male feathers influence how successful he will be mating; for females, feathers are a way for males to look at females and determine their health, which would determine if the female is a desirable mate. Different colors of feathers can help birds camouflage, which allows them to protect themselves. Feathers are also useful in helping birds fly, which is important for them to be able to move far distances and find food. The structure of feathers, a large surface area, helps the bird perform this function (Cornell-Feathers and Plumages). It is thought that as bird evolved from reptiles, epidermal scales have evolved into feathers, which provide better protection for birds, offering an evolutionary advantage (Dhouailly, D) .In addition, as birds and mammals have evolved, having feathers and hair has helped these animals maintain an endothermic lifestyle (Dhouailly, D).
ReplyDeleteJust like feathers, there are many purposes for hair in a mammal. Feathers and hair have similar structures, and they serve similar functions; however, feathers are found in birds and hair is found only in mammals. Some functions that hair serves include warmth, insulation, and retaining moisture. The structure of hair consists of proteins and sebaceous glands which secrete oil. This oil helps to trap moisture, which is important for the animal (Bergman, J). The smooth muscle, Arrector pili, runs from the epidermis to the base of the hair shaft. When it's cold, this muscle causes the hair to stand on its end, which is what we call goosebumps. The purpose of this structure is to help keep mammals warm. There are many theories about the evolution of hair. One theory is that it arose only to support the endothermic lifestyles of mammals (Bergman, J). Other theories include that hair arose from feathers in birds, or that hair has evolved multiple times in history (Bergman, J). Thinking about hair and the evolution of animals, it makes sense that evolution has favored animals with lots of hair that have a useful function for it. For example, evolution would favor polar bears with more hair, because the hair would help them survive in a cold environment.
Like hair, mammary glands are only found in mammals. The main purpose of mammary glands is to provide milk for mammals to feed their young with. The structure of mammary glands consists of a system of ducts with a glandular tissue. The structure of the glandular tissue helps the mammals perform the function of delivering milk. Mammary glands likely evolved with milk teeth as a means of getting nutrients without having to bite into food (University of Michigan).The structure of the mammary glands (allowing suckling and not biting to get milk) correlates with the function of delivering nutrients to animals that do not have teeth capable of biting. Although hair, feather, and mammary glands all have similar functions, such as providing animals with nutrients and warm, their structures are different because they more specifically reflect the lifestyle of the animal that they belong to.
Sources:
http://www.birds.cornell.edu/AllAboutBirds/studying/feathers/
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2736124/
http://www.creationresearch.org/crsq/articles/40/40_4/Bergman.htm
http://animaldiversity.ummz.umich.edu/site/topics/mammal_anatomy/mammary_glands.html
Marissa Lobl marissa.lobl@gmail.com