The correct answer is the organ.
The multicellular species are formed of various parts, which are required for survival. These parts are differentiated into the levels of the organization. There are five different levels, which are named as cells, tissue, organs, organ systems, and organisms.
When two or more layers of tissue function together, they produce an organ. All the animals comprise vital organs, without which they cannot survive. These include the kidneys, liver, lungs, brain, and heart.
Quick Answer. Collagen is the protein that all animals have in common, even single-celled animals and creatures such as sponges that lack differentiated bodies. Collagen is a cable-like protein that can calcify into bone, shell or other hard structures.
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MARK BRAINLIEST PLZ!!!!!!!!
The Silurian period occurred before the Neogene period.
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