Survival + Response Flashcards
What is a stimulus?
A detectable change to the internal or external environment
eg:
- temperature
- smell
- light
What is a receptor?
A cell or organ that detects a change in the internal or external environment
What is an effector?
A cell, tissue, organ or system that carries out a response (often a muscle or gland)
What is a response?
A change brought about due to a stimulus
- responses will generally be designed to enhance the animals chance of survival + pass on the advantageous allele to offspring
What is taxes?
Directional movement in response to external stimulus
Positive = towards stimulus
Negative = away from stimulus
Towards light = positive phototaxis
Away from chemicals = negative chemotaxis
e.g. Earthworm moving away from light (negative phototaxis)
What is kinesis?
Animals respond to stimulus but it’s not directional
-The more unpleasant the stimulus, the faster + the more changes of direction are seen in the animals movement
-Aids survival as animal is more likely to find favourable conditions where it will slow down + stop changing direction
-eg: woodlice moving to damp areas so they don’t dry out
What are tropisms?
When plants respond to a directional stimulus via a growth - increase a plants likelihood of survival
eg:
-Towards light: positive phototropism
-Away from gravity: negative geotropism
-Towards water: positive hydrotropism
What are the roots and shoots of plants in relation to gravitropism + phototropism?
Roots- Positively gravitrophic (growing towards gravity) + negatively phototrophic (growing away from light)
Shoots- Negatively gravitrophic (grow against gravity) + positively phototrophic (grow towards light)
What are plant growth factors and where are they produced?
Chemicals that regulate plant growth response to directional stimuli
Produced in plant growing regions (meristems)
What is IAA?
A plant growth factor
IAA is a type of auxin produced in roots + shoots of flowering plants
- It controls cell elongation
- Causes elongation of shoot cells but inhibits elongation in root cells
Describe positive gravitropism in flowering plants
- Cells in tip of root produce IAA which is transported along shoot
- IAA is initially transported to all sides of root
- Gravity influences movement of IAA from upper side to lower side of root
- A greater conc of IAA builds up on lower side than upper side
- As IAA inhibits elongation of root cells, the cells on this side elongate less
- Due to a faster elongation on upper side the root bends downwards towards gravity
Describe positive phototropism in flowering plants
- Cells in tip of shoot produce IAA which is transported down shoot
- IAA is initially transported evenly throughout all regions
- Light causes movement of IAA from light side to shaded side
- A greater conc of IAA build up on shaded side
- As IAA causes elongation of shoot cells, the cells on shaded side elongate more
- Due to faster elongation on shaded side the shoot tip will bend towards light
Describe negative phototropism in flowering plants
- In roots a higher conc of IAA inhibits cell elongation, causing root cells to elongate more on the lighter side and so the root bends away from light
Describe negative gravitropism in flowering plants
- IAA will diffuse from upper side to lower side of shoot
- If plant is vertical, this causes plant cells to elongate + plant grows upwards
- If plant is on its side, it will cause the shoot to bend upwards
What is a reflex arc + what are the stages?
The simplest response to a stimuli- the pathway of neurones involves in a reflex
1- Stimulus
2- Receptor
3- Sensory neurone
4- Coordinator in CNS (relay neuron)
5- Motor neurone
6- Effector (muscle or gland)
7- Response
-Response is rapid, short-lived, localised + involuntary
