Communication and homeostasis 5.1

Question 1

what is a stimulus?

Answer 1

response to a change in the environment

Question 2

how are stimulus detected?

Answer 2

by receptors

Question 3

what is an effector?

Answer 3

brings out a response

Question 4

what are examples of effectors?

Answer 4

muscle/glands

Question 5

how does the body maintain the internal environment once too much carbon dioxide has been produced?

Answer 5

. reduced pH detected
. greater breathing activity
. expels CO2 out of the body
. reduces respiration rate

Question 6

why do multicellular organisms need a communication system?

Answer 6

respond to changes in the internal and external
environment

to coordinate the activities of
different organs

Question 7

in what ways do organisms response to a stimulus?

Answer 7

changes its behaviour/physiology

Question 8

give three examples of stimuli an organism could respond to

Answer 8

. changes in temperature
. predation
. light intensity

Question 9

define paracrine signalling

Answer 9

signalling between cells that are close together (adjacent)

Question 10

define endocrine signalling

Answer 10

signalling between cells that are far apart, which involves the signalling molecule being transported in the circulatory system (distant)

Question 11

what is negative feedback?

Answer 11

to keep the body conditions at an optimum

Question 12

explain the negative feedback loop

Answer 12

. A receptor (or sensor) – to detect a stimulus

. A coordination system (nervous system and endocrine system) – to transfer information between different parts of the body

. An effector (muscles and glands) – to carry out a response

Question 13

why is homeostasis important- 1st reason

Answer 13

enzyme activity- maintains pH and temperature in the body

Question 14

why is homeostasis important- 2nd reason

Answer 14

cell size- changes in water potential affects the amount of water in tissue fluid and cells which can cause it to swell, burst or shrink

Question 15

why is homeostasis important- 3rd reason

Answer 15

independence from external conditions- animals with a constant internal environment can maintain a constant level of activity regardless of their environment

Question 16

how is negative feedback controlled

Answer 16

. receptors detect a change in stimulus which triggers a corrective mechanism when the factor is too low or too high

Question 17

what is positive feedback?

Answer 17

enhance the effect of the original stimulus

Question 18

give an example for when positive feedback is used

Answer 18

during childbirth, hormone oxytocin stimulates uterine contractions

this triggers a positive feedback reaction and more oxytocin is released initiating more contractions

Question 19

define thermoregulation

Answer 19

regulation of body temperature at an optimum

Question 20

why is thermoregulation important

Answer 20

maintain body at optimum temperatures for enzymes to work

Question 21

describe ectotherms and give examples

Answer 21

unable to maintain internal body conditions so rely on external sources such as sunlight

e.g reptiles and amphibians

Question 22

describe endotherms and give examples

Answer 22

they’re able to generate their heat metabolically by maintaining a constant internal body temperature.

e.g mammals and birds

Question 23

what are ways ectotherms control their body temperatures when it is too cold?

Answer 23

basking - absorb energy from sun
changing colour to absorb more heat
increase surface area , absorb more heat

Question 24

what are ways ectotherms control their body temperatures when it is too hot?

Answer 24

shelter in burrows- keep cool
move to somewhere shady

Question 25

what are the advantages of ectothermy?

Answer 25

less food used in respiration
more energy/nutrients gained from food can be converted to growth
need to find less food
can survive long periods without food

Question 26

what are the disadvantages of ectothermy?

Answer 26

less active in cooler temperatures
at risk from predators
cant take advantage of food availability when cold