Survival and Response (14)

Question 1

What are plant growth factors?

Answer 1

chemicals that regulate plant growth in response to directional stimuli

Question 2

Where are plant growth factors produced?

Answer 2

in apical meristems

Question 3

What happens to plant growth factors?

Answer 3

diffuse from cell to cell/phloem via mass transport

Question 4

What are the 5 steps of positive phototropism in plants?

Answer 4

1) IAA is produced in tip and diffuses to shaded side of shoot
2) active transport of hydrogen ions into cell walls occurs as IAA diffuses
3) H-bonds between cellulose are disrupted and action of expansins causes cell to become more permeable to water
4) cells on shaded side elongate faster due to higher turgor pressure
5) shoot bends towards light

Question 5

What are the 5 steps of positive gravitropism in plants?

Answer 5

1) IAA is produced in tip and initially transported to all sides of the root
2) gravity causes IAA to accumulate on lower side
3) IAA inhibits the elongation of root cells where concentration is high
4) cells on upper side elongate faster as there is a low IAA concentration
5) root bends downwards

Question 6

What is meant by taxis?

Answer 6

directional movement in response to external stimulus

Question 7

What are the 2 types of movement?

Answer 7

kinesis
taxis

Question 8

What is meant by kinesis?

Answer 8

non-directional response to presence and intensity of external stimulus

Question 9

What is an advantage of kinesis and taxis?

Answer 9

maintain mobile organism in optimum environment

Question 10

What are the 5 differences between mammalian hormones and plant growth factors?

Answer 10

1) concentration
2) action
3) synthesis
4) transport
5) speed

Question 11

How do mammalian hormones and plant growth factors differ in terms of concentration?

Answer 11

MH - response not always dependent on concentration
PGF - response proportional to concentration

Question 12

How do mammalian hormones and plant growth factors differ in terms of action?

Answer 12

MH - bind to complementary proteins on target cells
PGF - can affect all cells

Question 13

How do mammalian hormones and plant growth factors differ in terms of synthesis?

Answer 13

MH - specialised glands
PGF - various tissues in growing regions

Question 14

How do mammalian hormones and plant growth factors differ in terms of transport?

Answer 14

MH - circulatory system
PGF - diffusion or phloem translocation

Question 15

How do mammalian hormones and plant growth factors differ in terms of speed?

Answer 15

MH - faster-acting (homeostasis)
PGF - slow-acting (plant growth)

Question 16

How do organisms respond to temperature and humidity and why?

Answer 16

via kinesis because there are less directional stimuli so often no clear gradient from one extreme to another

Question 17

How do you recognise kinesis in organisms movement?

Answer 17

• organism crosses sharp division between favourable and unfavourable environment + turning increases
• then organism moves considerable distance into unfavourable environment + turning slowly decreases, moves in long straight lines, sharper turns - leading to new environment

Question 18

What is a chi-squared test suitable for in terms of organisms movements?

Answer 18

suitable for determining if a factor has a significant effect on movement of an animal in a choice chamber