Answer: The answer is option B. Cell Walls
Explanation: Prokaryotic cells are much smaller than eukaryotic cells, have no nucleus, and lack organelles. All prokaryotic cells are encased by a cell wall. In eukaryotes, vertebrates don't have a cell wall but plants do.
Habitats provide organisms with the resources they need to to live as food and shelter.
Answer:
We can tell that extinctions have occurred in the past by looking at fossils in layers of sediments. If the amount of fossils found match you can infer that they are the same organism and they are extinct. If you can't match up the bones with any animal today.
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Osteoporosis, which literally means porous bone, is a disease in which the density and quality of bone are reduced. As bones become more porous and fragile, the risk of fracture is greatly increased. The loss of bone occurs silently and progressively.
