Topic 6 : 6.1.1 Survival and response

Question 1

What’s a stimulus ?

Answer 1

A change in an organism’s internal or external environment

Question 2

Why is it important that organisms can respond to stimuli?

Answer 2

Organisms increase their chance of survival by responding to stimuli

Question 3

What is a tropism?

Answer 3

● Growth of a plant in response to a directional stimulus
● Positive tropism = towards a stimulus; negative tropism = away from stimulus

Question 4

Summarise the role of growth factors in flowering plants

Answer 4

● Specific growth factors (hormone-like growth substances) eg. Auxins (such as IAA) move (via phloem or diffusion) from growing regions eg. shoot / root tips where they’re produced ● To other tissues where they regulate growth in response to directional stimuli (tropisms)