| Have you heard the term "knee-jerk reaction"? Doctors use a hammer like the one pictured here to strike a patient's knee in order to test their reflexes. | |
Watch the animation to see how the message is delivered from the nerves in the knee to the muscles that contract causing a jerk.
We know animals can respond to their environment. Do plants respond? Even though they can't move, they can make changes to maintain homeostasis. The picture on the right is a microscopic view of two guard cells (the green semi-circles) with an opening in the middle called a stomata. Plants can open and close the stomata in order to control the amount of water that is lost. |
 Source: Plant Stomata, Alex Costa, Wikimedia Commons |
Watch the video below to see how the stoma of a plant works.