Communication & Homeostasis

Question 1

Advantages of ectothermy

Answer 1

• do not use energy to keep warm
  —> therefore less food used in respiration
• more energy & nutrients from food can be used for growth
• can survive long without food

Question 2

Advantages of endotherms

Answer 2

-Body temperature doesn’t fluctuate with external temperature, therefore can maintain constant temp
-Remain active even when external temperatures are low
-> can take advantage of available prey & escape
-> can live in colder parts of the world

Question 3

behavioural endotherm responses if too cold

Answer 3

• move into the sun
• hot drink
• put more clothes on

Question 4

Behavioural endotherm responses if too hot

Answer 4

• move out of sun
• drink cold water
• panting / gasps
• remove clothing
• lying on ground

Question 5

Behavioural responses of ectotherms that are too cold

Answer 5

• move into the sun
• lie on surfaces
• increase body surface area exposed to sun

Question 6

Behavioural responses of ectotherms that are too warm

Answer 6

• move out of the sun/ go underground
• reduce body surface area exposed to the sun

Question 7

Body reactions if body / blood temperature too cold

Answer 7

1. Hypothalamus heat centre stimulated
2. Shivering
3. Vasoconstriction
4. Increased metabolic rate
5. Piloerection of hairs

Question 8

body responses if the body / blood temperature is too hot

Answer 8

heat loss centre in hypothalamus stimulated
- vasodilation
- decreased metabolic rate
- sweating
- flattening of hairs

Question 9

Disadvantages of ectothermy

Answer 9

• less active in cooler temperatures
  –> more at a risk of predators (as a result), as unable to escape
• cannot take advantage of food available when cold

Question 10

Do smaller or larger organisms have faster rates of respiration

Answer 10

Smaller organisms -> bigger SA:V -> faster heat loss -> faster rate of respiration

Question 11

Excretory organs

Answer 11

Liver
Lungs
Kidneys
Skin

Question 12

Feature of endotherm (ms)

Answer 12

Scales / hairs / fur to trap layer of heat

Question 13

How could positive feedback increase hypothermia’s effects? (4)

Answer 13

1. Lower temp = reduces molecule Ke
2. Enzyme activity slows
3. Respiration rate slows
4. Loss of metabolic heat generated, so more heat lost

Question 14

How does a negative feedback loop work

Answer 14

1. Stimulus (change away from optimum conditions)
2. Receptors (detect the change)
3. Communication system (informs effector & change is signalled to other cells)
4. Effector (brings about response which…
   - reverses change of conditions
   - causes a return to optimum conditions)

Question 15

How does a positive feedback loop work

Answer 15

1. Stimulus: Change away from optimum conditions
2. Receptors: detect change
3. Communication system: informs effector & change is signalled to other cells
4. Effector: brings response to increase the change of conditions

Question 16

How does cell signalling work (steps)

Answer 16

A cell releases a signal which is detected & responded to by other cells
(This is done as…)
- signal has specific shape which is complementary to the shape of that of the cell surface receptor
- binds to receptor
causes specific changes in the receptor

Question 17

How does flattening of hairs occur

Answer 17

1. Hair erector muscles react
2. Hairs lie flat
3. Prevents the hair forming an insulating layer of warm air between skin & hair, increasing heat loss

Question 18

How does sweating occur

Answer 18

1. Sweat glands secrete sweat to cool skin
2. Heat energy from the body is lost as sweat evaporates from the skin: this heat energy is used to converted H2O (l) to (g)

Question 19

How is metabolic rate decreased

Answer 19

1. Less thyroxine released from the thyroid gland
2. Decreased basal metabolic rate as a result
3. So less heat released from metabolic reactions

Question 20

How is metabolic rate increased

Answer 20

More thyroxine is released from the thyroid gland
Increased basal metabolic rate
So more heat released from exothermic metabolic reactions

Question 21

Thermoregulation process (due to the hypothalamus)

Answer 21

• hypothalamus = thermoregulatory centre of the brain
• regulates body temperature by monitoring blood temperature & initiating responses if too long
• there are cold / warm receptors in the skin: stimulated as are those in the hypothalamus
  -> response!

Question 22

Toxic waste products excreted

Answer 22

Urea (by kidneys)
CO2 (by lungs)
Bile pigments (found in faeces)

Question 23

Weaknesses of endothermy

Answer 23

• lots of energy used to maintain body temperature (especially in cold)
• needs more food
• may overheat in hot weather
• lower proportion of energy & nutrients from food used in growth

Question 24

What are ectotherms

Answer 24

They rely on external heat sources to maintain their body temperature therefore, body temp fluctuates with external temp

Question 25

What are endotherms

Answer 25

They can use heat from their own metabolic reactions to maintain their internal body temperatures within strict limits -> these detect external temperatures by hot and cold peripheral receptors

Question 26

What are features of a good communication

Answer 26

Enables cell to be in communication with each other Cover the whole body Enable short and long term responses Enable specific & rapid communication

Question 27

What are the two communication systems that work by cell signalling

Answer 27

Nervous System (Neuronal communication: CNS & PNS. The nerve impulses passed along neurons to send info through the nervous system.) Endocrine system (Hormonal communication produces hormone) They both co-ordinate and regulate body functions

Question 28

What do communication systems do

Answer 28

Allow animals & plants to respond to changes in internal & external environments

Question 29

What do effectors (/cell/tissues/organs) do

Answer 29

Bring about a response

Question 30

What do endotherms do (not temp wise, HEAT wise:

Answer 30

Sometimes needed for ms They GENERATE HEAT (energy) from metabolic processes / respiration

Question 31

What do receptors do

Answer 31

Monitor and detect stimuli (changes to the environment)

Question 32

What do to about aquatic ectotherms (e.g think of waters high SHC)

Answer 32

- water temp is way less variable that land due to waters high SHC Therefore, it’s easier for these ectotherms to maintain a stable internal body temperature within strict limits

Question 33

What does a negative feedback loop do

Answer 33

Reverses the effects of stimulus & brings the system back to optimum

Question 34

What internal conditions are maintained by homeostasis

Answer 34

pH Body temp Blood pressure Metabolic waste Blood glucose / salt / O2 / CO2 conc Water potential of the blood

Question 35

What is a positive feedback loop

Answer 35

It increases the effect of the stimulus and brings the system further away from optimum

Question 36

What is a response

Answer 36

How an organism changes its behaviour / physiology

Question 37

What is cell signalling

Answer 37

How cells communicate with each other

Question 38

What is homeostasis

Answer 38

Maintaining stable internal environment & conditions within narrow limits, despite changes in either/and internal & external environments Therefore, it maintains optimal conditions for enzyme activity & cell function

Question 39

What is shivering / effects

Answer 39

The regular & rapid relaxation & contraction of muscles Increases respiration rate More heat released

Question 40

What is vasodilation

Answer 40

1. Muscles in the arteriole walls relax 2. Arterioles near the skin dilate 3. More blood flows through the skin capillaries 4. More heat is lost to the environment

Question 41

What’s vasoconstriction

Answer 41

- muscles in arteriole wall contract - arterioles near the skin contract - less blood can flow through capillaries in skin - less heat lost to environment by radiation

Question 42

What’s an example of homeostatic control

Answer 42

Excretion - the removal of toxic waste products of metabolism from the body (via excretory organs)

Question 43

What’s are stimuli

Answer 43

External environmental changes

Question 44

What’s piloerection

Answer 44

1. Hair erector muscles contract 2. Hairs stand on end 3. Forms the insulating layer of warm air between the skins surface and hairs 4. So reduces heat loss

Question 45

What’s the standard homeostasis response pathway

Answer 45

A negative feedback loop

Question 46

What’s thermoregulation

Answer 46

- an example of a neg feedback loop The regulation of constant body temperature (for endotherms)

Question 47

Why is excretion important

Answer 47

Prevents build up of toxic waste products of metabolism If left to accumulate 1. They can interfere with cell processes by altering pH 2. May prevent normal metabolism 3. May act as an enzyme inhibitor & reduce activity