response to stimuli

• what is a stimulus

  detectable change in the internal or external environment
• what are stimuli detected by

  receptors
• what is the rwsponse produced by

  an effector
• what is an example of an effector


  muscle or gland
• what is the sequence of events in stimulus and response

  stimulus - receptor - coordinator - effector - response
• why must ogrnaisms respond to stimuli inn the environment


  in order to survive
• what must organisms by successful at doing in order to survive

  avoid being eaten

  finding favourable conditions for living

  finding food
• wjhat does a response to change require

  detection from a receptor cell
• what is the role of a receptor cell


  detects a stimulus
• what is a response


  an action an organism takes in response to a stimulus
• what are the different types of taxes

  food - tropho

  light - photo

  chemical - chemo

  sound - phono

  wind - anemo

  gradient - klino

  memory - mnemo
• what is trophism


  plant response to stimuli via growth
• what is a positive trophism


  movement towards a stimulus
• what is a negative trophism

  movement away from a stimulus
• what is trophism controlled by

  growth factor ie IAA
• what is IAA


  auxin that controls cell elongation in shoots and inhibits growth of cells in roots
• what is positive phototrophism


  plant grows towards sunlight
• what happens in phototophism in plant shoots

  IAA produced by root tip cells

  causes elongation in shoots

  IAA diffuses into other cells

  unilateral light - IAA diffuses into shaded side of shoot resulting in a higher concentration of IAA

  plant bends towards light as cells on shaded side elongate
• what happens in phototrophism in roots

  roots do not photosynthesise

  high concentration of IAA inhibits cell elongation

  higher concentration of IAA on shaded side

  roots elongate on lighter side

  root bends away from light
• what happens in Geotrophism in shoots

  IAA diffuses from upper side to lower side of shoot #

  if plant is verticle cells elongate and plant grows upwards

  if cel is on its side shoot bends upwards

  negative geotrophism

  IAA diffuses away from gravity
• what happens in geotrophism in roots

  IAA moves to the lower side of the roots

  upperside elongates of root bends down towards gravity

  IAA diffuses towards gravity

  anchors plant in - positive geotrophism
• what is the difference between IAA in the shoots and the roots

  shoots - IAA promotes cell elongation

  roots - IAA inhibits cell elongation