Flashcards · Biology · Plant Adaptations and Hormones
Investigating Tropic Responses
-
What is the independent variable in the phototropism investigation?
The direction of the light.
-
What is the dependent variable?
The angle of bending of the shoots.
-
What does a clinostat do?
Turns the seedlings slowly, so gravity acts on all sides equally.
-
Why is a pot kept in the dark?
As a control, to show the growth without a direction of light.
-
Why use a pot lit from above?
To show that the shoots grow straight with light from all around.
-
What do roots do in a dish on its side?
Curve downwards.
-
What do shoots do in a dish on its side?
Curve upwards.
-
Why are the gravity dishes kept in the dark?
So that light does not affect the direction of growth.
-
Name two control variables.
Any two from: type of seed, temperature, water, distance from lamp, time.
-
How is the angle of bending measured?
With a protractor, on the seedling or on a photograph.
-
How is the mean calculated?
Add all of the angles, and divide by the number of seedlings.
-
Why use many seedlings?
To get a reliable mean, and to spot anomalies.
-
Why can the lamp affect the results?
It can warm one side of the seedlings.
-
Why wash hands after the investigation?
Mould may grow on damp seeds and cotton wool.
-
Why is a photograph useful?
It gives a record, and can be used to measure the angle accurately.
-
Common mistake about the dark pot?
Thinking it has no growth. The shoots grow, but straight and pale.