Homeostasis

Question 1

Why is a communication system necessary?

Answer 1

Cells need to remain active, maintain certain set of conditions, temperature, pH, aqueous environment and freedom from toxins for enzyme function, communicate between cells in multicellular organism to do this

Question 2

What is a stimulus?

Answer 2

Any change in the environment that causes a response

Question 3

What is a response?

Answer 3

A change in behaviour or physiology as a result of a change in environment

Question 4

What external stimulus might an animal have to respond to?

Answer 4

External envrironmney will change, may place stress on organism, such as drop in temperature, water levels, time of day, season.

Question 5

What is the internal environment if an organism?

Answer 5

Internal cells and tissues bathed in tissue fluid, metabolic activities occur in cells, products and waste produced, may be toxic, diffuse into tissue fluid, needs to react to stop accumulation of excess waste and toxins.

Question 6

What is the effect of CO2 build up in cells?

Answer 6

Build up in tissue fluid could disrupt enzyme action by changing pH of environment around the cells

Question 7

How can environment of cells by maintained?

Answer 7

Blood system maintains composition of tissue fluid, waste likely I enter the blood and be carried away, excreted from the body. Concentrations in the body have to be closely monitored, to ensure balance is kept

Question 8

What is required in a good communication system?

Answer 8

Covers whole body
Enables cells to communicate with each other
Rapid communication
Specific communication
Short term or long term response
Required in multicellular organism as cells are differentiated, specialised to carry out different roles

Question 9

What is cell signalling?

Answer 9

One cell releases a chemical that is detected by another cell, which responds to signal

Question 10

What are the two major systems of communication?

Answer 10

Neuronal system, interconnected network of neurones, signal to each other across synapse junctions. Can conduct signal very quickly for rapid repose
Hormonal system, uses blood system, cells in endocrine gland release hormone into blood, carries all over the body to target cells, allows longer term responses

Question 11

What is homeostasis?

Answer 11

The maintainable of the internal environment in a constant state despite external changes

Question 12

Give some examples of conditions that have to be maintained in the cell?

Answer 12

Body temperature
Glucose concentration
Salt concentration 
Water potential
Blood pressure
Co2 concentration

Question 13

What is negative feedback?

Answer 13

Process that brings about a reversal of any change in conditions. Ensures that an optimum steady state is maintained, as the internal environment is returned to its original set of conditions after any change. Essential for homeostasis

Question 14

What is the standard pathway for response to a stimulus?

Answer 14

Stimulus, receptor, communication pathway, effector, response

Question 15

What is a sensory receptor?

Answer 15

Receptor are internal and monitor conditions inside the body, measure conditions and are stimulated to send signal if change is detected

Question 16

What is a communication system?

Answer 16

Such as neuronal and hormonal, acts by signalling between cells, transmits message from receptor cells to effector cells.

Question 17

What are effector cells?

Answer 17

Cells bring about response that reverses the change detected by receptor cells

Question 18

What is positive feedback?

Answer 18

A process that increases any change detected by the receptor, tends to be harmful and does not lead to homeostasisf

Question 19

Why might positive feedback be beneficial?

Answer 19

Pregnancy, cervix stretches, change signalled to anterior pituitary gland, stimulates it to secrete hormone oxytocin, increases contractions causing further dilation which releases more oxytocin, so baby can be born

Question 20

How might have responses to oxytocin and adrenaline have evolved?

Answer 20

Adrenaline cause fight or flight reflex, aids survival, can reproduce and pass in alleles that enabled it to survive . Oxytocin causes tend or befriend responses, if mother pacified predator then offspring more likely to survive

Question 21

What are the negative effects of positive feedback?

Answer 21

Fir example when body gets too cold, enzymes are less active, so less exergonic reactions, so less heat made in body, so body cooks even further, enzyme reactions become even slower

Question 22

What effect does temperature increase have in enzyme action?

Answer 22

As temp increases, enzyme activity increases, however above certain temperature and rate of reaction falls. Cell processes do not occur other proteins may also be denatured, so photosynthesis and respiration cannot occur etc

Question 23

What is an ectotherm

Answer 23

An organism that relies on external sources of heat to regulate its body temperature, tend to fluctuate with external temperature,

Question 24

Advantages of being an ectotherm?

Answer 24

Less food used for respiration, less food required for survival and greater proportion of energy obtained from food can be used for growth

Question 25

What are the disadvantages of being an ectotherm?

Answer 25

Less active in cooler temperatures l, need to warm up before activity so at greater risk of predation, may not be capable of activity in the winter

Question 26

How does an ectotherm regulate its temperature?

Answer 26

Changes behaviour and physiology to increase absorption/loss of of heat from/to its environment

Question 27

What adaptations can increase heat gain from surroundings?

Answer 27

Expose body to the sun, orientate body to the sun, alter body shape

Question 28

What adaptations can cause heat loss to surroundings?

Answer 28

Orient ate body away from the sun, hide in burrow, alter body shape, increase breathing movements

Question 29

Temperature if bee swarms maintained at 35 degrees, how might this be achieved?

Answer 29

Bees in middle of swarm Warner, move towards outside, transfers heat, in hot weather, more passages of air flow created, so cooler air cab carry heat away, fewer passages in colder weather

Question 30

What is an endotherm?

Answer 30

Organism that can use internal sources of heat, such as heat generated from metabolism in liver to maintain its body temperature

Question 31

What are advantages of being and endotherm?

Answer 31

Fairly constant body temperature despite external conditions, activity possible in cold weather so can inhabit colder parts of the planet

Question 32

What are the disadvantages of being and endotherm?

Answer 32

Significant part of energy intake used for body temperature, more food required each day and less of energy from food used for growth, so more food needed

Question 33

How can sweat glands maintain temp?

Answer 33

If too hot, secrete more sweat onto skin, uses heat from blood for latent heat of vaporisation If too cold, less sweat secreted, less evaporation of water so less loss of latent heat

Question 34

How do lungs, mouth and nose maintain temp?

Answer 34

Panting increases evaporation if water using latent heat | If cold animal doesn't pant

Question 35

How can hairs in the skin maintain temp?

Answer 35

If hot, hairs lie flat, provide little insulation so heat loss by convection and radiation If cold hairs raised and trap later if insulating air, reducing heat loss

Question 36

How do arterioles in leading to capillaries in skin affect temperature

Answer 36

Too hot, Vasodilation allows more blood into capillaries near skin surface, more heat radiated Too cold, vasoconstriction, reduces blood flow through capillaries, less heat radiated

Question 37

How do liver cells maintain body temp?

Answer 37

Too hot, rate of metabolism reduced, less heat generated from exergonic reactions such as respiration Too cold, rate of metabolism increased, more gear from metabolism

Question 38

What behavioural mechanisms do endotherm a have if too hot?

Answer 38

Move into shade, decrease SA exposed to the sun, remain inactive

Question 39

What behavioural mechanisms do endotherm a have if too cold?

Answer 39

Move into sunlight, orientate body to sun, move to generate heat is muscles

Question 40

How is core temperature regulated?

Answer 40

Temperature of blood regulated in hypothalamus, if core temp fluctuates from optimum, hypothalamus sends signals to reverse change.

Question 41

What are peripheral receptors?

Answer 41

Thermoregulatory centre in hypothalamus monitors blood temperature, and detects any change, early warnings from extremities could stops too much variation of core temperature, of extremities start to cool down peripheral receptors in the skin send information to Thermoregulatory centre so can initiate behavioural mechanisms to maintain core temp

Question 42

Why does shrew have to eat body mass in food each day, but elephant eat less than 1%?

Answer 42

Shrew very small so has large SA to volume rare, loses a lot it heat through skin do lots of food needed to replace hear, elephant had much smaller ratio do loses much smaller proportion of its body heat

Question 43

Why are Australian penguins much smaller than Antarctican penguins?

Answer 43

Australia much warmer so do not need to be large to maintain temp, Antarctica much cooler, so need smaller SA:V ratio to maintain temp better