HS - LS1.A - Feedback Mechanisms - FINAL (ACM 1/30/2014)

Module: Feedback Mechanisms

DCI: LS1.A (D) Feedback mechanisms maintain a living system’s internal conditions within certain limits and mediate behaviors, allowing it to remain alive and functional even as external conditions change within some range. Feedback mechanisms can encourage (through positive feedback) or discourage (negative feedback) what is going on inside the living system.

 PE: HS-LS1-3 Plan and conduct an investigation to provide evidence that feedback mechanisms maintain homeostasis.

 [Clarification Statement: Examples of investigations could include heart rate response to exercise, stomate response to moisture and temperature, and root development in response to water levels.] [Assessment Boundary: Assessment does not include the cellular processes involved in the feedback mechanism.]

The ideas in this standard are: 

- feedback mechanisms maintain internal conditions

- feedback mechanisms mediate behaviors

- feedback mechanisms allow the living system to remain alive

- feedback mechanisms all the living system to remain functional 

- feedback mechanisms can encourage what is going on inside the living system (positive feedback)

- feedback mechanisms can discourage what is going on inside the living system (negative feedback)

In order to address the content portion of this standard, we can provide examples of feedback responses in living systems and ask general questions.  For our TEK on homeostasis, we gave a lot of scenarios and asked kids to tell how a living thing would respond to that change.  For this standard, those kinds of questions are probably not the way to go. 

Possible Question Starters: 

"Some students are observing stomate of a leafy plant under a microscope.  They record the following data in a table. 

Time (hours)	External Condition	Stomata
2	Dry	Closed
6	Moist	Open
10	Dry	Closed

This data provides evidence of a feedback mechanism because -"

correct answer -  the stomate open and close in response to changing external conditions

incorrect answer - the stomate open and close at regular intervals throughout the day

"Students recorded their heart rates in several situations. Which of the following data collected would illustrate a feedback response?"

correct answer - a heart rate increase when the students exercise

incorrect answer - a student's heart remains consistent while at rest

incorrect answer - all of the students' heart rates within a close range