The cells of all organisms produce waste materials that must be removed or the cell will die. Organisms must also rid
themselves of waste products in order to survive. The process
by which both cells and organisms rid themselves of waste
materials is known as:
Respiration
Digestion
Excretion
Reproduction

An ecologist studied the same species of deer during the summer and the winter. she noticed that during the summer, when there was plenty of food, the deer were energetic and playful. however, during winter when food was scarce, the deer moved more slowly and did not run unless they needed to escape a predator. which scientific fact is best supported by her observations?