Homework. Watch the Bozeman video called, Positive and Negative Feedback Loops. Read Feedback Control on p. 673 and 674

Transcription

1 Homework Watch the Bozeman video called, Positive and Negative Feedback Loops Read Feedback Control on p. 673 and 674

2 Objective: You will be able to explain how negative feedback regulates growth and reproduction, and to maintain dynamic homeostasis Do Now: Read the Enduring understanding sheet

3 Essential Knowledge: Organisms use feedback mechanisms to maintain their internal environments and respond to external environmental changes. Negative feedback Positive feedback

4 Negative Feedback Negative feedback mechanisms maintain dynamic homeostasis for a particular condition (variable) by regulating physiological responses, returning the changing condition back to its target set point. Examples: Temperature regulation in animals Plant responses to water limitations

5 Temperature Regulation in Animals

6 Negative feedback Figure Pathway Stimulus Example Low ph in duodenum Go through the steps in the diagram Turn to a partner and explain to them why it is an example of negative feedback Endocrine cell Hormone S cells of duodenum secrete the hormone secretin ( ). Target cells Blood vessel Pancreas Response Bicarbonate release

7 Negative feedback Figure 32.11c Stimulus Sensory neuron TSH circulation throughout body Hypothalamus Neurosecretory cell Thyroid gland TRH Thyroid hormone Thyroid hormone circulation throughout body TSH Anterior pituitary Response

8 Prokaryotic cells find it necessary at times to synthesis one amino acid into a different amino acid that it does not get from its external environment. An example is shown to the right. Make a claim about the effect on this organism if a mutation in the threonine deaminase enzyme negatively impacted its allosteric site. Justify your claim Provide reasoning for your prediction.

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11 The endocrine system incorporates feedback mechanisms that maintain homeostasis. Which of the following demonstrates negative feedback by the endocrine system? (A) (B) (C) (D) During labor, the fetus exerts pressure on the uterine wall, inducing the production of oxytocin, which stimulates uterine wall contraction. The contractions cause the fetus to further push on the wall, increasing the production of oxytocin. After a meal, blood glucose levels become elevated, stimulating beta cells of the pancreas to release insulin into the blood. Excess glucose is then converted to glycogen in the liver, reducing blood glucose levels. At high elevation, atmospheric oxygen is more scarce. In response to signals that oxygen is low, the brain decreases an individual s rate of respiration to compensate for the difference. A transcription factor binds to the regulatory region of a gene, blocking the binding of another transcription factor required for expression.

12 The endocrine system incorporates feedback mechanisms that maintain homeostasis. Which of the following demonstrates negative feedback by the endocrine system? (A) (B) (C) (D) During labor, the fetus exerts pressure on the uterine wall, inducing the production of oxytocin, which stimulates uterine wall contraction. The contractions cause the fetus to further push on the wall, increasing the production of oxytocin. After a meal, blood glucose levels become elevated, stimulating beta cells of the pancreas to release insulin into the blood. Excess glucose is then converted to glycogen in the liver, reducing blood glucose levels. At high elevation, atmospheric oxygen is more scarce. In response to signals that oxygen is low, the brain decreases an individual s rate of respiration to compensate for the difference. A transcription factor binds to the regulatory region of a gene, blocking the binding of another transcription factor required for expression.

13 Individual Work Complete the Feedback Mechanism Packet These experiments are confusing at first, make sure you read and reread each one!

14 Objective: You will be able to explain how positive feedback regulates growth and reproduction, and to maintain dynamic homeostasis Do Now: Read the Enduring understanding sheet

15 Positive Feedback Positive feedback mechanisms amplify responses and processes in biological organisms. The variable initiating the response is moved farther away from the initial setpoint. Amplification occurs when the stimulus is further activated which, in turn, initiates an addition response that produces system change. Examples Ethylene production in fruit Cells of the immune system.

16 Ethylene

17 HIV is a virus that attacks the Helper T-Cells. Predict the impact that HIV will have on the biological system represented below. Justify your response.

18 Complete the Feedback Question sheet

19 Alteration in the mechanisms of feedback often results in deleterious consequences. Examples: Diabetes Mellitus in response to decreased insulin Dehydration in response to decreased antidiuretic hormone (ADH) Blood clotting

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21 Dehydration in response to decreased antidiuretic hormone (ADH)

22 Blood Clotting How might a disruption of this system affect the homeostasis of an organism?

23 Homework Watch the Bozeman video called, Response to External Environments

24 Objective: You will be able to justify the selection of data needed to answer a question about the relevant mechanism an organism uses to respond to a change in their external environment. Do Now: Brainstorm some ways that animals respond to their external environment. Generate a list of examples.

25 Organisms respond to changes in their environment through behavioral and physiological responses. Examples: Phototropism and photoperiodism in plants Hibernation and migration in animals Shivering and sweating in humans

26 Describe the kind of data that could be collected to provide a direct answer to the question, do plants respond to changes in light direction?

27 Biological Clocks and Circadian Rhythms Many plant processes oscillate during the day Some plants lower their leaves in the evening and raise them in the morning, even when kept under constant light or dark conditions Describe the kind of data that could be collected to provide a direct answer to the question, do plants respond to circadian rhythms?

28 Photoperiodism Physiological reaction of organisms to the length of day

29 Paired Work Design an experiment to test the physiological or behavioral response of an organism to a change in its environment. You can use an example below or choose one on your own. Be sure to: Pose a scientific question State independent and dependent variables Identify a control and controlled variables State a hypothesis Justify the selection of data that would prove your hypothesis correct. Behavioral response examples Hibernation in animals Migration in animals Shivering and sweating in humans Share your experiment with another pair