Communication and Homeostasis

Question 1

What conditions does a cell need to maintain in their cells

Answer 1

-A suitable temperature
-A suitable pH
-An aqueous environment that keeps substrates in a solution
-Freedom from toxins and excess inhibitors

Question 2

Stimulus/response

Answer 2

Stimulus - Change in environment
Response - The way in which an organism changes its behaviour or physiology

Question 3

Example of an organism reacting to a change in the environment

Answer 3

The arctic fox has a thicker white coat in the winter and a thinner grey/brown coat in the summer
Whitecoat - insulation and camouflage

Question 4

Example of a multicellular organism reacting to a change within its internal environment

Answer 4

Build up of waste may act directly on the cells which respond by reducing activity so less waste is produced - response may not be good for the organism

Question 5

What is the composition of the tissue fluid maintained by

Answer 5

The blood - takes waste products away

Question 6

Why is a multicellular organism more efficient than a unicellular organism

Answer 6

Its cells are differentiated- cells are specialised to perform particular functions

Question 7

What makes a good communication system

Answer 7

-Covers the whole body
-Cell communication
-Specific communication
-Rapid communication
- Short term and long term repsonses

Question 8

Two major systems that work by cell signaling:

Answer 8

Neuronal
Hormonal

Question 9

Homeostasis

Answer 9

Maintaining a constant internal environment despite changes in the external and internal factors

Question 10

Aspects maintained by homeostasis

Answer 10

-Body temperature
-Blood glucose concentration
-Blood salt concentration
-Water potential of the blood
-Blood pressure
-Carbon dioxide concentration

Question 11

Input and output of negative feedback

Answer 11

Change away from optimum - Receptor detects change - Communication system informs effector - Effector reacts to reverse change -returns to optimum

Question 12

For negative feedback a number of processes must occur:

Answer 12

-A change in the internal environment must be detected
-The change must be signaled to other cells
-There must be an effective response that reverses the change in conditions

Question 13

Endotherms

Answer 13

An organism that uses heat from metabolic reactions to maintain body temperature
-Controls body temperature within strict limits

Question 14

Endotherms are exogenic

Answer 14

Release energy in the form of heat
-increasing respiration
-Directing blood towards or away from the skin

Question 15

Endotherms - Skin response if the body is too hot

Answer 15

-Sweat glands secrete fluid onto the skin surface as this evaporates it uses heat from blood as latent heat of vaporisation
-Hairs and feathers lie flat to reduce insulation and allow greater heat loss
-Vasodilation of arterioles direct blood to the skin surface so more heat can be radiated away from the body

Question 16

Endotherms - Skin response if the body is too cold

Answer 16

-Less sweat is secreted so less evaporation means less heat loss
-Hairs and feathers stand erect to trap air which insulates the body
-Vasoconstriction of arterioles leading to skin surface direct blood away from the skin and less heat is lost

Question 17

Endotherms - gaseous exchange response if the body is too hot

Answer 17

Some animals pant increasing evaporation from the surface of lungs and airways
Evaporation uses heat from blood

Question 18

Endotherms - gaseous exchange response if the body is too cold

Answer 18

Less panting so less heat is lost

Question 19

Endotherms - liver response if the body is too hot/cold

Answer 19

Less respiration / increases respiration so more energy from food is converted to heat

Question 20

Endotherms - skeletal muscle response if the body is too hot/cold

Answer 20

Fewer contractions/spontaneous muscle contractions (shivering)

Question 21

Endotherms - blood vessel response if the body is too hot/cold

Answer 21

Dilation / constriction

Question 22

Behavioral responses if the body is too hot - endotherms

Answer 22

Hide away from the sun
Orientate body to reduce surface area exposed to sun
Remain inactive
Wet skin uses evaporation to help cool the body

Question 23

Advantages of endotherms

Answer 23

-Maintain a fairly constant body temperature
- Remain active when external temperatures are low which means can escape predators
-inhabit colder parts of the planet

Question 24

Disadvantages of endotherms

Answer 24

-Use a significant part of their energy to maintain body temperature if cold
-Need more food
-Use for growth a lower proportion of energy and nutrients gained from food
-May overheat in hot weather

Question 25

What detects a change in the body’s core temperature

Answer 25

Temperature receptors (thermoregulatory centre) in the hypothalamus - then send out impulses to cause different responses which will reverse this change
Neurons - quick responses
Hormones - Long term

Question 26

If core body temperature is too low the hypothalamus will bring about:

Answer 26

-Changes in the skin to reduce heat loss
-Release of heat through extra muscular contraction
-Increased metabolism in order to release more heat from exergonic reactions

Question 27

What detects a change in temperature in extreme cases

Answer 27

Periphral temperature receptors in the skin

Question 28

Ectotherms

Answer 28

An organism that relies on external sources of heat to maintain body temperatures
-Cannot control body temperatures as effectively as endotherms
-Body temperature fluctuates with external temperature

Question 29

If ectotherms are too hot/cold

Answer 29

Behavioral responses
Too hot:
-Move into a sunny area
-Lie on a warm surface
-Expose a larger SA to the sun

opp/if too hot

Question 30

Snake behavioral adaption and benefit

Answer 30

Basks in the sun - absorbs heat directly from the sun

Question 31

Locust behavioral adaption and benefit

Answer 31

Early morning locusts sit side in exposing a larger SA to the sun but at midday head n exposing a smaller SA
Increase breathing rate and depth of breathing movements - more water evaporates from the tracheal system cooling the body

Question 32

Lizard behavioral adaption and benefit

Answer 32

Hide in a burrow when hot and coolest parts of the day - underground has more stable temperatures

Question 33

Horned lizard behavioral adaption and benefit

Answer 33

Can change shape by expanding/contracting ribcage - expanding increases SA exposed to the sun

Question 34

Advantages of ectotherms

Answer 34

-Less food used in respiration
-More energy and nutrients from food for growth
-Need less food
-Survive long periods without food

Question 35

disadvantages of ectotherms

Answer 35

Less active at cooler temperatures means more at risk with predators and cannot take advantage of available food

Question 36

Mammals response to external environment - EQ-

Answer 36

1) peripheral / skin , thermoreceptors / (heat) receptors ,
stimulated (by decrease in external temp) ;
2) (impulses sent to / blood temperature monitored in )
hypothalamus / sensory cortex ;
3) vasoconstriction of , arterioles / small arteries , to reduce heat loss ;
4) (prevents heat loss by) radiation / conduction / convection ;
5) increased , metabolic rate / metabolism / respiration ,
to generate heat (energy) ;
6)(release of) adrenaline / thyroxine ;
7) shivering / (involuntary) muscle spasms , to generate heat (energy) ;
8) erector / hair , muscles raise , (skin) hair / fur , to trap , air / heat ;