Homeostasis Reading Activity

Feedback Mechanisms Structure and Function Homeostasis Reading Activity Activity   Each team member is assigned to read one of the three articles on how homeostasis is maintained: 1) your eyes, 2) contractions during the birth process, and 3) turgor pressure in plants. You will have an opportunity to share what you have learned with your team members. Introduction: Homeostasis is one of the fundamental characteristics of living things. It refers to the maintenance of the internal environment within tolerable limits. For example, all sorts of factors affect the suitability of our body fluids to sustain life; these include properties like temperature, salinity, acidity, and the concentrations of nutrients and wastes. Because these properties affect the chemical reactions that keep us alive, we have built-in physiological mechanisms to maintain them at desirable levels. When a change occurs in the body, there are two general ways that the body can respond. In negative feedback, the body responds by stopping and reversing the direction of change. Because this tends to keep things constant, it allows us to maintain homeostasis. On the other hand, positive feedback is also possible. This means that if a change occurs in some variable, the response is to change that variable even more in the same direction. This has de-stabilizing effect, so it does not result in homeostasis. Positive feedback is used in certain situations when relatively rapid change is desirable. Overall. Negative feedback is far more common than positive feedback. Readings 1, 2, and 3 are on subsequent pages. 1 Feedback Mechanisms Structure and Function Homeostasis Reading Activity Activity, continued   Reading 1: The pupil of the eye responds to changes in light. Light has to reach the back of the eye to allow us to see. However, too much light reaching the back of the eye makes seeing harder and can damage the eye. When a person enters a dark room, the constriction of the pupil is stopped and the pupils in both eyes will dilate, allowing all the available light to enter the eye. On the other hand, when a person walks outside in bright sunlight, too much light reaches the back of the eye. The pupils in both eyes constrict, allowing only enough light to enter. Constriction and dilation of the pupil is critical to all organisms that use vision. Nocturnal animals, such as jaguars, must be able to use the light of the moon to hunt. On the other hand, diurnal animals such as deer must be able to see predators even in bright light. Write a claim, provide your evidence by drawing and labeling your graph, and include reasoning to help describe how an organism’s eyes are regulated to maintain homeostasis. Notes: *Write whether it is a negative or positive feedback loop. *Evidence - Reading 1 & 2 evidence should be a graph. #3 could just be bullet points. *Ignore the thing below reading 3 *Reasoning - Should be paragraph long Size of pupil Organism's eyes are regulated to maintain homeostasis through negative feedback loops. Negative feedback loops try to remove the stimulus trying to get back to homeostasis, and in this case that would be the eyes constricting for enough light to enter. According to the graph, Light units the darker the stimulus is the larger the pupil will dilate, which is a positive feedback loop adding on to the stimulus. However, as the light increases, the pupil will constrict, allowing only enough light to enter. This is the result of a negative feedback, as negative feedbacks try to remove the stimulus to get back to homeostasis. Therefore, organism's eyes are regulated to maintain homeostasis through negative feedback loops. 2 Feedback Mechanisms Structure and Function Homeostasis Reading Activity Activity, continued   Reading 2: When a woman is ready to give birth, the baby’s head puts pressure on the uterine wall which sends impulses to the brain to start contractions. The woman’s uterus in response will constrict to push the baby into the birth canal, and the uterus will have increasing contractions. This process ebbs and flows so that the baby can slowly move through the birth canal during labor. This also allows the mother’s body to go with the contraction in a rhythmic cycle to not stress the mother’s body or the baby. Once the uterus has enough strong contractions, the baby is pushed out the birth canal, and the body continues having contractions to get rid of the placenta. Write a claim, provide your evidence by filling in the diagram, and include reasoning to help describe how the mother’s body cycles through labor rhythmically. The mother's body cycles through labor rhythmically, because the contractions allow the passage of the baby through the uterus and birth canal. This also allows the baby and the mother to not get hurt. According to the text, 1) "...will constrict to push the baby into the birth canal, and the uterus will have increasing contractions... so that the baby can slowly move through the birth canal during labor" 2)"Once the uterus has enough strong contractions, the baby is pushed out the birth canal..." 3)"This also allows the mother's body to go with the contraction in a rhythmic cycle to not stress the mother's body or the baby" As shown in the text, these contractions allow the baby and the mother's body to not stress and let the baby slide through the birth canal. After each contraction, the uterus releases, making it loser and loser each time. Not to mention, each time, more pressure is added each time allowing the baby to exit the birth canal. Therefore, the mother's body cycles through labor rhythmically, because the contractions allow the passage of the baby through the uterus and birth canal 3 Feedback Mechanisms Structure and Function Homeostasis Reading Activity Activity, continued   Reading 3: The pressure that exists in a plant cell is called turgor pressure. Turgor pressure causes water to move through the cell membrane, either in or out of the cell, to maintain a constant concentration of water and minerals critical to their function. If the concentration of water and some minerals becomes too high, the action is reversed. The transpiration (loss of water) is stopped and additional water enters the cell to correct the problem which causes higher turgor pressure (plant is upright). If the concentration becomes too low, water passes out of the cell (transpiration increases) again to correct the problem by causing lower turgor pressure (plant wilts). If the external environment does not improve, the plant will die. Write a claim, provide your evidence by filling in the diagram, and include reasoning to help describe how a plant regulates its water and mineral concentrations by using turgor pressure. A plant regulates its water and mineral concentrations by using turgor pressure, through transpiration. Transpiration is similar to homeostasis as it lowers or adds water to correct the problems. According to the text, 1) "The transpiration(loss of water) is stopped and additional water enters the cell to correct the problem which causes higher turgor pressure" 2) "If the concentration becomes too low, water passes out of the cell(transpiration increases) again to correct the problem by causing lower turgor pressure" As shown in the text, transpiration uses processes similar to homeostasis. An example is when the concentration becomes too low water passes out of the cell to define the turgor pressure. As a result, transpiration uses negative and positive feedback loops to correct the problems causing a change in the turgor pressure, and then the plant regulates its water and mineral concentrations. Therefore, a plant regulates its water and mineral concentrations by using turgor pressure, through transpiration. 4