Answer:
Plants take in Carbon Dioxide and filter it releasing oxygen.
Shelled protozoans became part of 7 layers
Tissues
Tissues are somewhat more complex units than cells. By definition, a tissue is an organization of a great many similar cells with varying amounts and kinds of nonliving, intercellular substance between them.
Before puberty, children do have an estrogen level in their body. This is only truly noticeable around the time of puberty. It's always there, but not hyperactive until puberty.
