The lining of the uterus is shed because an ovum has not been fertilized
I think that this would be carbohydrates, I'm not completely sure though.
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The very function, or job of CELL MEMBRANES is to protect the cell from it's surroundings, or in other words, to keep it safe. It controls the movement of substances in and out of cells and organelles, like a guard watching for suspicious activity and protecting something.
The cell membrane itself is a thin, flexible layer around the cells of all living things. It separates the inside of the cells from the outside of the cells.
B Nature selection for traits the allow for increased rates of reproduction and survival over traits that don't, is correct.
A is also correct
A makeshift increment in the squirrel proliferation rate.
