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A Level Biology - Unit5 > Homeostasis > Flashcards

Flashcards in Homeostasis Deck (16):

What do organisms use to detect and respond to any changes to the steady state of the body?

Chemical systems (using hormones and glands)
Electrical systems (using neurones and receptors)


Define homeostasis.

An organism maintains a dynamic equilibrium with small fluctuations over a narrow range of conditions.


Describe how a negative feedback system works.

Small change in one direction is detected by sensory receptors.
Effectors work to reverse the change and restore normal body conditions.
They reverse the initial stimulus.


Give three examples of negative feedback systems.

Control of blood sugar levels using insulin and glucagon.
Temperature control.
Control of water balance in the body.


Describe how a positive feedback system works.

Small change to internal environment is detected by sensory receptors.
Effectors are stimulated to reinforce the change and increase the response.


Give two examples of positive feedback systems.

Blood clotting cascade- platelets are stimulated to be released.
During childbirth- head of baby presses against cervix and stimulates hormone oxytocin to keep being released.


What is meant by latent heat of evaporation?

Objects cool down as water evaporates from a surface


What is radiation?

Transmission of electromagnetic waves to and from the air, water or ground.


What is convection?

The heating and cooling by currents of air or water, (warm air rises and cooler air sinks) setting up convection currents around an organism.


What is conduction?

Heating as a result of the collision of molecules. Air is not a good conductor of heat but ground and water are.


What are the 4 main ways in which animals warm up?

Waste heat from cell respiration.
Conduction FROM surroundings.
Convection FROM surroundings.
radiation FROM surroundings.


What are the main ways animals cool down?

Evaporation of water.
Conduction TO surroundings.
Convection TO surroundings.
Radiation TO surroundings.


What is an ectotherm?

Use their surroundings to warm their bodies up. Heavily dependent on the environment to maintain their core body temperature.


What is an endotherm?

Rely on their metabolic processes to warm up.
Usually good at maintaining a core body temperature regardless of the environmental conditions.


What behavioural responses have ectotherms developed to help them maintain their core body temperature? (5 main ones)

1) Bask in the sun.
2) Orientate their bodies so maximum surface area faces the sun.
3) Extend parts of their body so more SA exposed to the sun.
4) Pressing their bodies against warm surfaces and rocks.
5) Contract their muscles/vibrate their wings to increase cellular metabolism.
6) Opens mouth and pants to cool down
(reverse all these to cool down)


What physiological responses do ectotherms have that help maintain their core body temperature?

1) Dark coloured skin to absorb more radiation
2) Alter heart rate to increase/decrease metabolic rate
3) Require less food as they use less energy to regulate temperatures.