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A2 OCR Biology F214 > Homeostasis > Flashcards

Flashcards in Homeostasis Deck (17)
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1
Q

Give two examples of external stimuli

A
Temperature
Oxygen concentration
Sunlight level
Water availability 
Nutrient levels 
Predation
Competition
2
Q

Give two examples of internal stimuli

A
CO2 levels
O2 levels
Blood glucose 
Temperature
Water levels
Salt levels
3
Q

What are the two methods of cell signalling

A

The Nervous System

The endocrine system

4
Q

What is the nervous system?

A

Interconnected neurones which signal to each other across synapse junctions

5
Q

What is the endocrine system

A

Secretes hormones directly into the blood

6
Q

Define homeostasis

A

The maintenance of internal environmental conditions despite external fluctuations

7
Q

Define negative feedback

A

The process which brings about a reversal in the change of internal conditions
e.g. Thermoregulation

8
Q

Define positive feedback

A

The process which increases any change detected by the receptors
e.g. Oxytocin and birth

9
Q

Define ectotherm

A

An animal that is dependent on external sources of body heat

10
Q

Define endotherm

A

An animal that is dependent of the internal generation of heat

11
Q

Give one example of both a physiological and behavioural response of an ectotherm

A

Physiological- lizards open their frills to absorb more heat from the sun
Behavioural- snakes bask on hot rocks

12
Q

Give one example of both a physiological and behavioural response of an endotherm

A
Physiological-
•sweat glands 
•panting
•hairs on skin
•vasodilation
•skeletal muscle
Behavioural-
•move to shade or into sunlight
13
Q

Why do organisms need to respond to changes in their environment?

A

To survive

14
Q

Explain the difference between positive and negative feedback

A

Negative feedback monitors a change and initiates a process to reverse the change whereas positive feedback will increase the change.

15
Q

Why is it important to maintain a constant body temperature?

A

If body temp is too low, enzyme activity falls and the rate of metabolism drops. High temp. denatures proteins such as channel proteins in the membranes.

16
Q

Explain how basking can help regulate body temperature

A

If an ectotherm is too cool it can absorb heat from the rock and direct from the sun. This will warm up the skin and the blood flowing near the surface which will warm muscles.

17
Q

Explain how vasoconstriction helps reduce heat loss.

A

It reduces blood flow through the skin, blood flows through vessels deeper in the body. Heat is less easily radiated out from the body.