5.1.1 - Communication and Homeostasis

Question 1

Why do multicellular organisms need communication systems?

Answer 1

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

Question 2

How do cells transfer signals?

Answer 2

• locally (eg. across synapses)

- across long distances (using hormones)

Question 3

What is homeostasis?

Answer 3

maintaining a stable internal environment regardless of changes in the external environment

Question 4

What are receptors?

Answer 4

glycoproteins that detect changes in our body and send a signal which triggers a response

Question 5

What are effectors?

Answer 5

part of the body that carries out a response to a stimulus

eg. gland, muscle

Question 6

What is a negative feedback loop?

Answer 6

a mechanism that reverses a change in the body to return to optimum conditions

Question 7

Name some examples of a negative feedback loop

Answer 7

regulating blood glucose levels

thermoregulation

Question 8

What happens in a negative feedback loop?

Answer 8

• change away from optimum
• receptors detect change
• communication system informs effector
• effector reacts to reverse change
• returns to optimum

Question 9

What is a positive feedback loop?

Answer 9

a mechanism that amplifies a detected change, moving the conditions away from the normal level

• accelerate a biological pathway
  eg. uterus contraction during birth, formation of a blood clot after an injury, etc

Question 10

Name some examples of a positive feedback loop?

Answer 10

uterus contraction during childbirth

formation of a blood clot at the site of a wound

Question 11

What are the differences between negative and positive feedback?

Answer 11

Negative feedback:
-resists change
-more common
Positive feedback:
-amplifies change
-speeds up change/process
-less common

Question 12

What is thermoregulation?

Answer 12

control of internal body temperature

Question 13

Why is thermoregulation important?

Answer 13

temp effects enzymes (if too high, they denature)

Question 14

What are endotherms?

Answer 14

animals which maintain a very stable body temperature by relying on metabolic processes

• warm blooded animals
  eg. mammals, birds

Question 15

What are ectotherms?

Answer 15

animals which are unable to control their body temperature so rely on external sources of heat and behavioural mechanisms

• cold blooded animals
  eg. reptiles, fish, amphibians

Question 16

What are the advantages of being an ectotherm?

Answer 16

• use less energy to maintain body temp
• don’t need as much food (less needed for respiration)
• greater proportion of energy used for growth

Question 17

What are the disadvantages of being an ectotherm?

Answer 17

• extreme weather conditions can make them suffer
• basking in the sun makes them more exposed to predators
• metabolic reactions are slower
• less active in cooler temps

Question 18

What are the advantages of being an endotherm?

Answer 18

• can survive in a larger range of temps
• have a constant body temp (regardless of external temps)
• less risk of predators (active when cool)

Question 19

What are the disadvantages of being an endotherm?

Answer 19

• need to eat more food (need more for respiration) so can’t survive for as long without food
• less energy is used for growth

Question 20

How do endotherms regulate temperature?

Answer 20

physiological responses and behavioural responses

Question 21

How do ectotherms regulate temperature?

Answer 21

behavioural responses

Question 22

How do endotherms control body temperature using physiological responses?

Answer 22

• thermoreceptors detect changes in body temp
• thermoreceptors send out a nerve impulse, which travels along a sensory neurone to the hypothalamus in the brain
• hypothalamus sends a nerve impulse along a motor neurone to an effector
• the effector responds to alter the body temp

Question 23

What physiological responses do endotherms have to reduce body temperature?

Answer 23

• vasodilation
• sweating
• hairs lie flat

Question 24

What physiological responses do endotherms have to increase body temperature?

Answer 24

• vasoconstriction
• shivering
• hormones
• reduced sweating
• hairs stand up

Question 25

What behavioural responses do ectotherms have to control body temperature?

Answer 25

• expose body to sun
• increase breathing rate
• change body shape
• change body movement