5.1 COMMUNICATION/HOMEOSTASIS

Question 1

Describe the need for communication systems in multicellular organisms

Answer 1

• To respond to changes in the external/internal environment to coordinate activities of different organs

Question 2

Which communication system is used for adjacent cell signalling?

Answer 2

• Neuronal system

Question 3

Which communication system is used for distant cell signalling?

Answer 3

• Hormonal system

Question 4

Define homeostasis

Answer 4

• The maintenance of a constant internal environement about the norm despite the changing environment

Question 5

Define negative feedback

Answer 5

• Mechanism that reverses a change to bring the system back to optimum conditions

Question 6

Define positive feedback

Answer 6

• Mechanism that increases a change to take the system further away from optimum conditions

Question 7

Define thermoregulation

Answer 7

• Regulation of internal body temperature

Question 8

State which part of the brain and receptor is used for thermoregulation in endotherms

Answer 8

• Hypothalamus
• Peripheral thermoreceptors

Question 9

Define ectotherm

Answer 9

• Organisms that cannot regulate internal body temperature so behaviour relies on external environment to maintain temperature

Question 10

Define endotherm

Answer 10

• Organisms that can regulate internal body temperature using metabolic reactions for heat

Question 11

State what ectotherms do when body temperature is too low

Answer 11

• Move to sunny area
• Lie on warm surface
• More surface area exposed to sun

Question 12

State what ectotherms do when body temperature is too high

Answer 12

• Move out of sun
• Go underground
• Reduce the surface area exposed to sun

Question 13

Explain five actions of endotherms when temperature is too high

Answer 13

1) Increased sweating (evaporates heat away)
2) Vasodilation (blood is closer to skin surface so more heat radiated away)
3) Hairs lie flat (reduces insulation)
4) Less respiration (less energy converted to heat)
5) Panting (evaporation of water from lung surface)

Question 14

Explain four actions of endotherms when temperature is too low

Answer 14

1) Vasoconstriction (blood is further from skin surface so less heat radiated away)
2) Shivering (muscle contractions release heat)
3) Skin hairs erect (trap air for insulation)
4) Increased respiration (more energy converted to heat)

Question 15

State two advantages of ectotherms

Answer 15

• Less food required
• Energy from food can be used for growth

Question 16

State two disadvantages of ectotherms

Answer 16

• Cannot rely on food for energy
• Inactive at cold temperatures

Question 17

State three advantages of endotherms

Answer 17

• Body temperature fairly constant
• Remain active when external temperatures are low
• Can inhibit the cold areas

Question 18

State three disadvantages of endotherms

Answer 18

• Require more food
• Lower proportion of food energy used for growth
• Use a significant part of energy intake to maintain body temperature in cold conditions