Homeostasis

Question 1

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

Answer 1

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

Question 2

Define homeostasis.

Answer 2

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

Question 3

Describe how a negative feedback system works.

Answer 3

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.

Question 4

Give three examples of negative feedback systems.

Answer 4

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

Question 5

Describe how a positive feedback system works.

Answer 5

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

Question 6

Give two examples of positive feedback systems.

Answer 6

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.

Question 7

What is meant by latent heat of evaporation?

Answer 7

Objects cool down as water evaporates from a surface

Question 8

What is radiation?

Answer 8

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

Question 9

What is convection?

Answer 9

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

Question 10

What is conduction?

Answer 10

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

Question 11

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

Answer 11

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

Question 12

What are the main ways animals cool down?

Answer 12

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

Question 13

What is an ectotherm?

Answer 13

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

Question 14

What is an endotherm?

Answer 14

Rely on their metabolic processes to warm up.

Usually good at maintaining a core body temperature regardless of the environmental conditions.

Question 15

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

Answer 15

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)

Question 16

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

Answer 16

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.