I/E: Responses in Plants/Animals Flashcards
Tropism
The response of a plant to a directional stimulus.
Positive tropism
Plant growth towards the stimulus.
Negative tropism
Plant growth away from the stimulus.
Phototropism
- Positive phototropism*
- Negative phototropism*
Growth of a plant in response to light.
- Positive = growth towards light*
- Negative = growth away from light*
Gravitropism
- Positive gravitropism*
- Negative gravitropism*
Growth of a plant in response to gravity
- Positive = growth towards gravity/downwards*
- Negative = growth away from gravity/upwards*
Phototropism/gravitropism of roots?
Phototropism/gravitropism of shoots?
Roots = negatively phototropic, positively gravitropic.
Shoots = positively gravitropic, negatively gravitropic.
Growth factors
Hormone-like chemicals that speed up or slow down plant growth.
How do plants respond to directional stimuli?
Where are these produced?
Using growth factors produced in the growing regions of the plant, eg. the roots and the shoots.
Auxins
Growth factors that stimulate the growth of shoots by cell elongation.
What does high concentrations of auxins in the roots of a plant do?
Inhibits the growth of roots.
Cell elongation
Cell walls of plants become loose and stretchy, so the cell gets longer.
Name an auxin:
Indoleacetic Acid (IAA)
Where is IAA produced?
Why is it moved around plants?
In the tips of shoots in flowering plants.
Moved around the plant to control tropisms.
How does IAA move around a plant:
- long distance?
- short distance?
What does this movement result in?
Short distance = diffusion and active transport
Long distance = via the phloem
Results in an uneven distribution of IAA and uneven growth.
Describe the tropisms that occur in the shoots of flowering plants:
- Phototropism = IAA concentration increases on shaded side of shoot = cells elongate and shoot bends towards the light.
- Gravitropism = IAA concentration increases on the lower side of the shoot = cells elongate and shoot grows upwards.
Describe the tropisms that occur in the roots of flowering plants:
- Phototropism = IAA concentration increases on shaded side = growth is inhibited so root bends away from light.
- Gravitropism = IAA concentration increases on the lower side = growth is inhibited so root grows downwards.
What are the two responses of simple organisms?
Tactile responses (taxes)
or
Kinetic responses (kineses)
Tactile responses
Organisms move towards or away from a directional stimulus, eg light.
Give an example of a tactile response in woodlice:
- Phototaxis - move away from a light source.
- Helps them survive:
- Keeps them concealed under stones during the day (safe from predators)
- Keeps them in damp conditions (reduces water loss)
Kinetic responses
Organisms’ movement is affected by a non-directional stimulus, eg. humidity.
Give an example of a kinetic response in woodlice:
- High humidity = move slowly and turn less often, so that they stay where they are.
- Low humidity = move faster and turn more often, so that they move in to a new area.
- Increases chances of moving into a high humidity area, and improves survival by reducing water loss.
What is a choice chamber and what is it used to investigate?
Container with different compartments, in which you can create different environmental conditions.
Can investigate how animals respond to certain conditions.
Describe an investigation using choice chambers to investigate animal responses:
- Split choice chamber into 4 conditions.
- Damp/dark
- Dry/dark
- Damp/light
- Dry/light
- Place 10 woodlice on the mesh in the centre of the chamber and cover with the lid.
- After 10 minutes, take off lid and record the number of woodlice in each condition.
- Repeat.
