Why do animal cells have many small vacuoles and plant cells have 1 or 2 large vacuoles?

In which situations is the principle of cross-cutting relationship useful in determining relative age?

Which of the following is most likely the result of an organism having lipids in its body a) water cannot be absorbed through the surface of a leaf b)human eats fruits to get a quick source of energy c) a sheep sleeps for more hours in the winter d) a warm river is filled with fish and algae

In which energy level are valence electrons located?