Survival and Response Flashcards
Organisms [1] their chance of survival by responding to [2] in their environment.
[1] increase
[2] changes
List two simple responses by small organisms such as insects
Taxis
Kinesis
Function of taxis and kinesis for mobile organisms
- Keep organisms in a favourable environment.
(e.g. more food, more mates, less predators, less desiccation) - Increase chances of survival
Define taxis
Directional movement in response to a stimulus
Positive taxis
Directional response with movement towards the stimulus
Negative taxis
Directional response with movement away from the stimulus
Define kinesis
Random OR non-directional movements in response to the stimulus
Give one similarity and one difference between a taxis and a tropism.
similarity − directional response to a stimulus / movement towards OR away from a stimulus;
Difference − in taxis whole organism moves whereas tropism a growth response in part of the plant (e.g. shoot or root tips).
OR
Difference - taxis occurs in animals whereas tropisms
In flowering plants, specific [1] factors move from growing regions to other tissues, where they regulate growth in response to directional [2].
[1] growth
[2] stimuli
Which organisms demonstrate tropisms?
Plants
Define tropism
Response of a plant to a directional stimulus
Stimuli that cause tropisms
Light
Gravity
Water
Salinity
Positive phototropism
Directional response of shoot tips towards light
Directional response of root tips away from light
negative phototropism
Positive gravitotropism
Directional response of root tips towards gravity
Auxis are a family of growth factors that cause tropisms. Which specific auxin must you know.
IAA
Full name: Indoleacetic acid
Where is IAA synthesised?
Shoot tips &
root tips
How does IAA move into the growing region of the shoot or root tip?
Diffusion
Where does IAA build up in the shoot tips in response to light?
On the shaded side
Effect of IAA in the shoot tips
- Stimulates elongagation of cells on the shaded side;
- Causes shoot to bend towards the light;
(this is a positive phototropism)
Where does IAA build up in the root tips in response to gravity?
On the side closest to gravity / on the underside
Effect of IAA in the root tips
Inhibits elongagation of cells on the underside;
Cells on opposite side (away from gravitiy) can elongate and cause the root tip to bend towards gravity;
When a young shoot is illuminated from one side, IAA stimulates growth on the shaded side.
Explain why growth on the shaded side helps to maintain the leaves in a favourable environment (2 marks).
- Causes plant to bend / grow towards light / positive phototropism;
- Light energy required for photosynthesis;
TRUE or FALSE:
IAA is only produced in the light
FALSE
IAA is produced in the light AND dark
Which neuron in the simple reflex arc contains receptors to the stimulus?
Sensory
Suggest two advantages of simple reflexes
Rapid;
Protect against damage to body tissues;
Do not have to be learnt / innate behaviour / involuntary;
Help escape from predators;
Enable homeostatic control;
Finding suitable conditions / keep organism in favourable environment;
Give two types of cell that act as effectors.
Muscles
Glands
(which produce hormones)
What is found between the sensory neuron and relay neuron
synapse
