Responsiveness, Sensitivity, and Irritability in Living Organisms

How do organisms respond to changes in their environment besides movement?

What is the purpose of blood vessels dilating in mammals in response to a rise in body temperature?

Which of the following is NOT an example of stimuli that organisms can detect?

What coordinates activities within an organism?

What are examples of means through which organisms receive information?

Which of the following is NOT an effector that organisms use to respond to stimuli?

Responsiveness in Living Organisms

All living organisms respond to changes in their internal and external environment to maximize their chances of survival.
A stimulus (singular) or stimuli (plural) triggers a response in an organism, such as rapid withdrawal of a hand from a hot object or growth towards sunlight in green plants.

Types of Stimuli

Examples of stimuli include changes in light, sound, heat, chemicals, and mechanical contact.

Detecting Stimuli

Organisms must have means of receiving information, such as eyes, ears, and taste buds, to detect stimuli.

Coordinating Activities

A system of nerves and chemical regulators called hormones coordinate activities within an organism.

Responding to Stimuli

Organisms respond to stimuli by means of effectors such as muscles and glands.
Energy is generally used in the process of responding to stimuli.

Examples of Responses

Trees lose their leaves in autumn in response to shortened hours of sunlight.
Blood vessels in the skin of mammals dilate (increase in diameter) in response to a rise in body temperature, helping to return the body to its optimum temperature.

Explore how living organisms respond to changes in their internal and external environments, known as stimuli, to maximize their chances of survival. Learn about examples of reactions to stimuli and responses in various organisms, such as rapid withdrawal from a hot object and growth towards sunlight.