Reptiles, birds, and mammals are amniotes. In addition to an amniotes egg then m

Question

Reptiles, birds, and mammals are amniotes. In addition to an amniotes egg then mom ancestor of all reptiles, birds, and mammals had a thick epidermal layer of scales partially composed of a protein called keratin Keratinized skin helps prevent water lines in a terrestrial environment. a. What type (or form) of keratinized epidermal structure represents the ancestral character state for all reptiles, birds, and mammals? b. Mammals have modified this features (question 8a) into what from? c. This modified from (question 8b) represents a shared [ancestral/derived (circle answer) character state that defines mammals. d. Are these two keratinized epidermal structures (questions 8a and 8b) homologous? Why? I have completed the online assignment for this week's lab activity. I understand that I may not attend lab without completing the entire pre-lab.

Explanation / Answer

Please find the answers and explanations below:

Part 8a: Keratin is a dense protein generally found as an outgrowth in the body to protect the inner-lying soft strctures from any damage. There are many forms of keratinized epidermal structures forund in reptiles, mammals and birds such as surface scales, integument extensions, nails, hooves, body hair, claws and talons along with horns and beaks.

Part 8b: The mammals have been evolved with development of body hair as a modification of this keratined epidermal growth. Presence of body hair is a characteristic feature of mammals only and also a taxonomical trait.

Part 8c: This modified trait in mammals is actually a derived trait, though it has ancestry with other animal species as well. This is because the mammals have been evolutinarily evolved as endothermal creatures and thus they require to modulate and regulate their body temperature on their own. Presence of body hair and thus surface hair mediated regulation of body temperature is thus a derived character for mammals.

Part 8d: The structures and organs of the body which share similar embroylogical features and functions are termed as homologous in nature. Since the structural and biological features of the body hair and epidermal keratin are similar in both mammals and non-mammals, these organs are indeed homologous in nature.

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