Stimuli and receptors 6.1

Question 1

What is a stimuli?

Answer 1

Changes to environment that organisms respond to
-eg light pain

Question 2

What is tropism?

Answer 2

A directional growth response of a plant to a stimulus
-positive grow towards
-negative grow away

Question 3

How do animals responds to stimulus (positive and negative)?

Answer 3

Positive move toward
Negative move away
Move away from unfavourable environments towards favourible environments

Question 4

What is taxis?

Answer 4

A directional movement towards a stimulus

Question 5

What is Kinesis?

Answer 5

A non directional movement to a stimulus
(involves increasing/decreasing random movements)

Question 6

Earthworms make less randoms turns untill they reach the dark, what type of behaviour is this?

Answer 6

Type of behaviour is kinesis because they are more likely to be underground so there as less likely to be predation(always give a specific survival advantage not just favourable environment)

Question 7

Some bacteria move away from waste products they produce, what type of behaviour is this?

Answer 7

Type of behaviour is negative taxis because they are moving away from a toxic substance

Question 8

What is IAA?

Answer 8

A growth factor in plants that stimulates or inhibits elongation
produced in root tip or shoot tip

Question 9

Where does IAA inhibit and stimulate elongation?

Answer 9

Root- inhibits elongation
Shoot- stimulates elongation

Question 10

Describe how positive phototropism occurs in plants shoot?

Answer 10

-IAA is produced in the shoot tip
-Moves to the shaded side of plant increasing its concentration
-IAA stimulates cell elongation on the shaded side of the plant
-More elongation occurs on the shaded side than the side facing the light causing the shoot to bend toward the light

Question 11

Describle how positive gravitropsim occurs in plants roots?

Answer 11

-IAA is produced in the root tip
-Moves to the lower side of the plant increasing its concentration
-IAA inhibits elongation at the lower side of the plant
-More elongation occurs on the upperside than the lower side causing the root to bend towards the lower side

Question 12

What is a reflex? 2 points

Answer 12

-RAPID, INVOLUNTARY responses to a stimulus -AND
-they do NOT need to be LEARNT

Question 13

Why do organisms need reflexes? 2 points

Answer 13

-To protect againts damage to bodytissues
-Can help escape from predators

Question 14

What in the reflex arc in the order of neurones with an example?

Answer 14

-Stimulus eg pain receptor
-sensory neurone
-intermediete neurone in spinal cord