The three-toed sloth often is camouflaged by algae. which type of symbiosis does this represent and why?

Many animals cannot sweat to maintain a stable body temperature. what is one other way animals can cool down?

An organ system consists of a group of organs that performs specific functions necessary for the survival of an organism. humans have eleven different organ systems: integumentary, skeletal, muscular, nervous, endocrine, circulatory, lymphatic, respiratory, digestive, urinary, and reproductive. discuss the function of neurons, the brain and the spinal cord within the human nervous system while explaining the interrelationship of each organ.

In general, characteristics that an organism survive and reproduce become more common over time. what mechanism of evolution causes this?