Survival and Response Flashcards
Taxis
directional response to stimulus
Kinesis
- random, non-directional response
- to non-directional stimulus
- changes in speed and rate of change of direction
Explain how organisms increase their chance of survival by detecting changes in their environment
- detect and move away from harmful stimuli
- increase chance of moving into favourable environment towards food etc.
Tropism
- growth of plant
- in response to directional stimulus
Auxin
- growth hormones
- made continually in shoots and roots
- indoleacetic acid (IAA)
Explain how IAA causes cell elongation in shoots
- acid growth hypothesis
- IAA causes H+ to be actively transported out of cytoplasm to spaces in cell wall
- acidification causes cell wall to be more plastic and elongate
Explain how IAA results in phototropic response in shoots
- light cause uneven distribution of IAA
- IAA moves from light side to accumulate on shady side of shoot
- IAA causes cell elongation
- bending towards light
Explain how IAA results in gravitropic response in roots
- IAA accumulates in underside of root
- due to gravity
- IAA inhibits cell elongation
- bending downwards
Suggest what experiment cutting off shoot tip proves
- shoot does not bend towards light
- tip produces response (contains IAA auxin)
Suggest what experiment placing lightproof cover over shoot tip proves
- shoot does not bend towards light
- light stimulus must be detected by shoot tip
Suggest what experiment removing shoot tip and inserting gelatin block between tip and rest of shoot proves
- shoot bends towards light
- chemical response not electrical
Suggest what experiment removing shoot tip and displaced to one side of shoot in darkness proves
- shoots bend towards sides without shoot tip
- bending is result of uneven distribution of hormone
- not light alone
Suggest what experiments placing glass plate between shoot to prevent and allow lateral transfer of IAA prove
- when glass plate prevents lateral transfer of IAA shoot does not bend towards light
- when glass plate allows lateral transfer of IAA shoot bends towards light
- IAA transported from light to shady side
- uneven distribution of IAA causes bending
- light does not inhibit or destroy IAA
Suggest how movement of maggots keep them moving rapidly out of unfavourable areas
- move faster
- change direction less often
- so keeps them moving in one direction
- stops them going around in circles
Central Nervous System
consists of brain and spinal cord