5.1.1 COMMUNICATION AND HOMEOSTASIS OCR BIOLOGY A LEVEL

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  • Created by: Davina1st
  • Created on: 17-03-22 18:55
Why do multicellular organisms need a communication system?
To detect/respond to changes in their internal/external environment (stimuli) in order to survive. Distance between receptors and effectors mean an advanced communication system is needed.
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What is homeostasis?
The ability to maintain a relatively constant internal environment despite external changes.
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What is cell signalling?
Nerve cells communicating with each other. One cell releases a chemical which has an effect on another cell, known as the target cell.
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Homeostasis is maintained by negative feedback. What is negative feedback defined as?
A system that acts to reverse a change.
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What is positive feedback?
A change in the internal environment is detected by sensory receptors and effectors are stimulated to increase the change. Not a homeostatic mechanism.
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What is thermoregulation?
The maintenance of a relatively constant core body temperature to maintain optimum enzyme activity.
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What are endotherms?
Use heat generated by metabolic processes to maintain a stable core temperature.
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What are ectotherms?
Maintain a stable core body temperature through external means.
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What is an example of an ectothermic behavioural response if it becomes too hot?
Shelter from sun/seeking shade, pressing the body against cool stone. Minimising movement to reduce metabolic rate.
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What is an example of an ectothermic behavioural response if it becomes too cold?
Conduction - pressing body against hot ground, exothermic metabolic reactions e.g. contracting their muscles and vibrating in iguanas and butterfly wings.
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What is an example of an ectothermic physiological response if it becomes too cold?
Having darker coloured skin in colder climates as it absorbs more radiation. Altering heart rate and increased metabolic rate to increasing warming to body surfaces.
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What is an example of an ectothermic physiological response if it becomes too hot?
Light coloured skin to absorb less radiation, decrease metabolic rate to decreased warming to body surfaces.
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How is core temperature increasing/decreasing above/below the norm detected in an endotherm?
Temperature change detected by thermoreceptors, which send a message to the hypothalamus in the brain, this coordinates a response to increase/decrease the body temp.
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What is a response to core temperature decreasing below the norm in endotherms?
Vasoconstriction-decrease loss of heat through radiation at skin. Decrease sweating to reduce heat loss by evaporation, hair stands on end=insulation, increased metabolic rate, shivering, finding sun (behavioural mechanism)
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What is a response to core temperature increasing the norm in endotherms?
Vasodilation-lose body heat through radiation, sweating to lose heat through evaporation, hair lies flat to reduce insulating effect, less movement to decrease metabolic rate
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Other cards in this set

Card 2

Front

What is homeostasis?

Back

The ability to maintain a relatively constant internal environment despite external changes.

Card 3

Front

What is cell signalling?

Back

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Card 4

Front

Homeostasis is maintained by negative feedback. What is negative feedback defined as?

Back

Preview of the front of card 4

Card 5

Front

What is positive feedback?

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Preview of the front of card 5
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