Survival and response Flashcards
What is a stimulus?
A detectable change in the internal or external environment
What is taxes?
A response where the organism will move its entire body towards a favourable stimulus or away from an unfavourable stimulus.
Moving towards - positive taxis
Moving away - negative taxis
What is kinesis?
A response where an organism changes the speed of movement and the rate it changes direction.
What will be the kinesis response if an organism moves from a beneficial stimuli to a harmful stimuli?
The kinesis response will be to increase the rate it changes direction and turn rapidly to quickly return to the favourable conditions
What will be the kinesis response if an organism is surrounded by harmful stimuli?
The rate it changes direction will decrease and the organism will move in a straight line to increase the chances of finding a new area with favourable conditions.
What is tropism?
A growth response by plants to a stimulus
What are the 3 things plants respond to?
Light, gravity and water
What are tropisms controlled by?
IAA
What is IAA?
A growth factor and a type of auxin that controls cell elongation in shoots and inhibits growth of cells in the roots.
Where is IAA found?
IAA is produced at the tips of shoots.
How does IAA move around?
They move by diffusion and active transport over short distances and through the phloem for long distances
What are the terms for a plant moving:
- Towards light
- Away from gravity
- Towards water
- Positive tropism
- Negative gravitropism
- Positive hydrotropism
Explain what happens to IAA when sunlight is evenly distributed over the shoot.
- The IAA will diffuse downwards, causing cells to elongate in the shoot and therefore the plant will grow upwards.
Explain what happens to IAA when sunlight is not evenly distributed over the shoot.
- The IAA will diffuse to the area with no sunlight which causes the cells on that side to elongate hence the plant will grow and bend towards the light source.
