How do the skin proteins—keratin, melanin, elastin, and collagen—each contribute to our physical identity? how about the dermal papillae?

Skin is the largest organ of our body and it contains a lot of immune barriers that protects the pathogens form entering the skin. Majorly the nature of skin also helps in the external appearance of a person and also denotes age.

The skin protein such as keratin, melanin, elastin, and collagen are extracellular matrix proteins that plays a major role in maintaining the elasticity and texture of the skin. The dermal papillae is the region that  is present in the outer most layer of the skin that helps in the formation of hair follicles.

organisms that lack symmetry are called asymmetrical and belong to phylum porifera/sponges.

organisms with specialized stinging cells belong to phylum cnidaria. stinging cells are called cnidoblast cells.

cnidarians show two morphological forms : polyp (sessile) and medusa (mobile)

filter feeding is observed in porifera members.  

alternation of generation is observed in coelenterata or cnidaria. there is alternation of asexual polyp form and sexual medusoid form. it is also referred as metagenesis.

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