Final answer:
Animals respond to environmental stimuli to protect themselves, find food, and reproduce. Complex sensory and nervous systems allow for these responses, which are critical for survival.
Step-by-step explanation:
Response to the Environment in Animals
Animals need to respond to their environment to survive and thrive. The ability to detect changes, whether it's a shift in temperature, the presence of predators, or the availability of food and mates, is crucial. When you accidentally step on a turtle instead of a rock, the turtle's response is to move or potentially snap at you. This response showcases the animal’s need to protect itself and respond to potential threats.
Animals can detect environmental stimuli such as light, sound, and touch through sensory nerve cells. These cells are part of the nervous system, which processes information and directs the body to respond accordingly. Behavioral responses serve several purposes: they enable animals to find food and mates and escape from predators. These actions demonstrate the importance of movement, which depends on the coordinated work of muscles and nerves.
Virtually all animals have internal digestion of food, another critical aspect of responding to the environment. Unlike other organisms that absorb nutrients directly, animals consume other organisms and may use specialized tissues and organs to digest them.
At the cellular level, individual cells must interact with their environment whether the organism is unicellular or multicellular. Complex mechanisms of communication within cells allow them to receive messages, transfer information across the plasma membrane, and produce internal changes in response to external stimuli.
Characteristics of Animals & Their Nervous Systems
Section 3.E.2 highlights that animals have nervous systems that detect both external and internal signals, transmit and integrate information, and produce responses. This system is fundamental to all living organisms, enabling them to react to their environment through various means such as eyes, ears, and other sensory structures.