Single-celled organisms are able to maintain homeostasis even though they lack higher levels of organization such as organs and organ systems because...

Because cells maintain homeostasis despite the amount.

Explanation:

When a change occurs in an animal’s environment, an adjustment must be made so that the internal environment of the body and cells remains stable. The receptor that senses the change in the environment is part of a feedback mechanism. The stimulus—temperature, glucose, or calcium levels—is detected by the receptor. The receptor sends information to a control center, often the brain, which relays appropriate signals to an effector organ that is able to cause an appropriate change, either up or down, depending on the information the sensor was sending.

because they are eaten by the frog and the frog getseaten by the snake and the snake by the eagle

the answer is d p: cell, q: organ, r: organ system, s: tissue