Frogs reproduce sexually. why do frogs require water to reproduce?

Punctuated equilibrium verses gradualism have long been contested as ways in which species evolve. choose the best evidence for gradualism.

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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.