Organisms respond to changes in their internal and external environments

Question 1

Nervous communication

Answer 1

The response to a stimulus is coordinated by the nervous system

Question 2

Sequence of events for nervous communication

Answer 2

stimulus–+ receptor –+ coordinator –+ effector –+ response

Question 3

What is simple reflex?

Answer 3

Rapid and involuntary response to a stimulus (not involving the brain) providing a protective effect

Question 4

Tactic response (taxis)

Answer 4

A simple directional response whose direction is determined by the direction of the stimulus (deliberate)

Question 5

Positive taxis

Answer 5

Movement towards the stimulus

Question 6

Negative taxis

Answer 6

Movement away from the stimulus

Question 7

Kinetic response (kinesis)

Answer 7

A non directional response in which the organism does not move towards or away from a stimulus (random). Instead, it changes the speed at which it moves and the rate at which it changes direction.

Question 8

Tropism

Answer 8

Response to a part of a plant towards a directional stimulus

Question 9

Positive tropism

Answer 9

Growth towards stimulus

Question 10

Negative tropism

Answer 10

Growth away from stimulus

Question 11

Plant growth factors

Answer 11

• Produced by cells in plants
• May also affect growth of tissues that release them not just distant target organ
• Exert influence by affecting growth

Question 12

Indoleacetic acid (IAA)

Answer 12

Belongs to a group of substances, auxins
-Controls cell elongation in plants
-Produced in the tips of shoots and roots

Question 13

Responses for plants

Answer 13

Light, Gravity, Water

Question 14

Phototropism (shoots)

Answer 14

Initially IAA is evenly distributed throughout regions
- Light intensity changes and auxins move from light side to shaded side of plant
- Causing shaded shoot to elongate
- Shaded shoots bend and grow at a faster rate than lighter side in direction of light
(positive phototropism)

Question 15

Phototropism (roots)

Answer 15

Initially IAA is evenly distributed throughout regions
- Light intensity changes and auxins move from light side to shaded side of plant
- Causing shaded roots to inhibit cell elongation
- Shaded roots bend and grow at a slower rate than lighter side in direction of light
(negative phototropism)

Question 16

Geotropism (shoots)

Answer 16

Initially IAA is evenly distributed throughout regions
- Moves to underside of plant causing elongation
- Lower side grows at a faster rate than upper side
- Moves upwards away from gravity
(negative geotropism)

Question 17

Geotropism (roots)

Answer 17

Initially IAA is evenly distributed throughout regions
- Moves to underside of plant inhibiting elongation
- Lower side grows at a slower rate than upper side
- Moves downwards towards gravity
(positive geotropism)

Question 18

Hydrotropism (roots)

Answer 18

Positive hydrotropism to direction of water

Question 19

Hydrotropism (shoots)

Answer 19

Negative hydrotropism away from water

Question 20

Thigmotropism

Answer 20

Plants able to climb and attach to other things when growing
Positive- move to stimulus
Negative- move away from stimulus

Question 21

What happens when you remove tips of shoots and roots?

Answer 21

It also removes IAA preventing ability to bend in a direction and grow