Ch14 Response to stimuli

Question 1

Stimulus

Answer 1

detectable change in the internal or external environment of an organisms that produces a response

Question 2

Taxis

Answer 2

Simple response whose direction is determined by the direction of the stimulus

Question 3

Positive taxis

Answer 3

Organism moves towards favourable stimulus

Question 4

Negative taxis

Answer 4

Organism moves away from unfavourable stimulus

Question 5

Stimulus selection pressure

Answer 5

1. ability to respond to stimuli
2. increase chance of survival
3. greater chance of reproduction
4. passing on alleles

Question 6

Single-celled algae

Answer 6

1. positive phototaxis- move toward light
2. increase chance of survival
3. increased photosynthesis will take place
4. increased manufacture of food

Question 7

Earthworms

Answer 7

1. negative phototaxis
2. increase chance of survival
3. move away from light towards soil
4. better able to conserve water, find food and avoid predators

Question 8

Bacteria

Answer 8

1. positive chemotaxis
2. move towards area with highly concentrated glucose
3. increased chance of survival
4. increased food source

Question 9

kinesis

Answer 9

Response which changes
1. the speed at which it moves
2. the rate at which it changes direction

Question 10

Advantage of kinesis

Answer 10

1. organism doesn’t move away from stimulus
2. increases chance of returning to favourable environment
3. important for when stimulus is less directional e.g. humidity or temperature
4. more intense the stimulus, the more rapid the movement

Question 11

Tropism

Answer 11

Growth of part of plant in response to directional stimulus

Question 12

Positive phototropism

Answer 12

1. cells in tip of shoot produce IAA, which is transported down the shoot
2. light causes movement of IAA to the shaded side of the shoot
3. greater concentration on shaded side
4. IAA causes elongation of shoot cells
5. shaded side of shoot elongates faster than light side, causing shoot tip to bend towards light

Question 13

Positive gravitropism

Answer 13

1.cells in tip of root produce IAA, which is transported along
2. gravity causes movement of IAA to the lower side of root
3. greater concentration on lower side
4. IAA inhibits elongation of root cells
5. upper side of root elongates faster than lower side, causing root tip to bend downwards towards gravity

Question 14

Favourable environment

Answer 14

1. rate of turning decreases
2. speed decreases
3. greater chance of staying in environment
4. higher chance of survival

Question 15

Unfavourable environment

Answer 15

1. rate of turning increases
2. speed increases
3. increases chance of moving to favourable environment
4. after while, move rapidly in straight lines

Question 16

Advantage of gravitropism

Answer 16

1. roots grow into soil
2. better able to absorb water and minerals
3. higher chance of survival

Question 17

Advantage of phototropism

Answer 17

1. plant shoot grows towards light
2. larger surface area covered
3. more photosynthesis can occur
4. higher chance of survival

Question 18

Plant growth factors

Answer 18

-affect growth
-made by cells throughout plant
-affect tissues that release them

Question 19

IAA

Answer 19

INDOLEACETIC ACID
1. increases plasticity of cell walls
2. active transport of H+ ions from cytoplasm in cell wall
3. allows cell to elongate by expansion
(acid growth hypothesis)

Question 20

Importance of reflex actions

Answer 20

1. automatic
2. avoid damage to tissues
3. balance
4. escape from predators