Tropisms Flashcards
What is taxis
A directional response towards or away from a stimulus
What is kinesis
A non-directional response to unfavourable environmental conditions
What does behaviour refer to
The observable coordinated responses an animal makes to stimuli in its environment
What is innate behaviour
instinctive behaviour which is genetically programmed so the organism responds to environmental circumstances
What does positive phototaxis refer to
Moving towards a light stimulus
What does negative phototaxis refer to
Moving away from a light stimulus
What does negative chemotaxis refer to
Moving away from a chemical stimulus
What does positive chemotaxis refer to
Moving towards towards a chemical stimulus
How would an organism act when performing kinesis
The organism would change the speed of movement and the rate at which it changes direction with the frequency of changing direction increasing in more unpleasant conditions
How would a woodlouse perform kinesis in unfavourable conditions
Woodlice prefer humid areas so if they enter a dry area the woodlouse would move rapidly and change direction to increase the chances of leaving the dry areas.
After a period of time if they haven’t found the humid area they will walk in a straight line to find it
What is a tropism
How plants respond to their environment
What type of tropism occurs when light is the stimulus
Phototropism
What is positive phototropism
Where the plant grows towards the light.
Where does positive phototropism occur
At the shoot tip
What is negative phototropism
Where the plant grows away from the light
Where does negative phototropism occur
At the roots
What type of tropism occurs when gravity is the stimulus
Geotropism
What is negative geotropism
Where the plant grows opposing gravity (up)
Where does negative geotropism occur
At the shoot tips
What is positive geotropism
Where the plant grows with gravity (down)
Where does positive geotropism occur
At the roots
How are the shoots of plants controlled by IAA 6 marks
- Cells in the tip of the shoot produces IAA which is then transported to the shoot
- The IAA is initially transported evenly throughout the plant as it moves down the shoot
3.However light causes movement of IAA from the light side to the shaded side of the shoot
- The greater conc of IAA builds up on the shaded side
- As IAA causes elongation of shoot cells there is a greater conc on the shaded side of the shoot so the cells on this side elongate more
- The shaded area elongates more than the light side causing the shoot tip to bend towards the light
How does IAA affect the shoot
Causes cells to elongate
How does IAA affect the roots
Inhibits cell growth
How are the roots of plants controlled by IAA 6 marks
- Cells in the root produces IAA which is then transported along the root
- The IAA is initially transported to all sides of the roots
3.Gravity influences the movement of IAA from the upper to lower side of the root
- A greater conc of IAA builds up on the lower side of the root
- As IAA inhibits elongation of root cells there is a greater conc on the lower side of the root so the cells on this side elongate less
- The relative elongation of cells on the upper side causes the roots to bend downwards with the force of gravity
sleep
If its late
Name the process by which IAA moves from the growing regions of a plant shoot to other tissues
Diffusion
