6.1.1 Survival And Response

Question 1

What is stimulus

Answer 1

A change in an organisms internal or external environment

Question 2

What is a tropism (negative and positive)

Answer 2

Growth in a plant in response to a directional stimulus

Positive tropism = towards stimulus
Negative tropism = away from stimulus

Question 3

How can IAA affect cells on roots and shoots

Answer 3

Shoots - high conc of IAA stimulates cell elongation

Roots-high conc of IAA inhibits cell elongation

Question 4

Gravitropism in flowering plants

Answer 4

Cells in top of shoot/root produce IAA

IAA diffuses down root/shoot

IAA moves to lower side of shoot/root (conc increases)

In shoots this stimulates cell elongation (roots inhibit)

So shoots bend away from gravity (roots bend towards gravity)

Question 5

Phototropism in flowering plants

Answer 5

Cell tip of shoot/root produce IAA

IAA diffused down shoot/root

IAA moves to shaded side of shoot/root so conc increases

Shoots - stimulates clear elongation (roots inhibit)

Shoots bend towards light (roots away from light)

Question 6

Responses that can maintain a mobile organism in an environment

Answer 6

Taxes:
-directional response
-moves towards or away from stimulus

Kinesis:
-non-directional
-speed of movement or rate of directional change changes in response to stimuli
-depending on intensity of stimuli

Question 7

Example of taxis and Kinesis response

Answer 7

Taxis - woodlice moving away from light to avoid predators

Kinesis - woodlice moving faster in drier environments to increase their chance of moshing to an area of higher humidity (won’t dry out)

Question 8

Explain the 3 neurons reflex

Answer 8

Receptor - sensory neurone - synapses - relay neurone- synapse - motor neurone- effector

Question 9

Positive effect of the reflex

Answer 9

Rapid (only 3 neurones)

Autonomic (no consciousness )

Protects harmful stimuli (predators)