With the beginning of the middle proterozoic comes the first evidence of oxgen build up in the atmosphere. with is catastrophe came eukaryotic forms. these include multicellular algae, and toward the end of the proterozoic the first animals
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Answer:
chromosomes
Explanation:
Thread-like structures that are found in the nucleus of a cell that contains all DNA. Each chromosome is made of protein and a single molecule of DNA. Human cell nucleus contains 46 chromosomes or 23 pairs. Half of these chromosomes come from one parent and half come from the other parent.
Answer:
Ozone layer... pollution
Explanation:
The ozone layer is a layer in the atmosphere which provides a barrier between harmful UV rays and the Earth. However, pollution is quickly depleting the layer which in turn creates a higher risk of skin cancers and other conditions caused by harmful UV rays.
