survival and response Flashcards
Stimulus
Detectable change in the internal/external environment of an organism that leads to a response.
Receptor
Detects stimulus and is specific to one type of receptor
Coordinator
Formulates a suitable response to a stimulus e.g. nervous system/ hormonal system.
Effector
Produces a response to a stimulus e.g. muscles/glands
How do organisms respond to a stimuli
(5 fingers)
Stimulus——>Receptor———————>Coordinator—-> Effector—–>response
Describe a reflex arc
Tip: should add to 7 fingers
Stimulus–>receptor—>sensory neurone—>relay neurone——->motor neurone——->effector—-> response
Importance of reflex arc
- rapid because only 3 neurones and few synapses
-Involuntary as doesn’t involve the brain
-Protects from harmful stimuli
Define Taxes
Directional movement by organisms who move towards a favourable stimulus or away from an unfavourable one
Example of taxes
Woodlice response to light as they move away from light as it keeps them away from predators and in damp conditions to reduce water loss so improves chances of survival
Define kineses
random movements towards a stimulus or away.
Example of kineses
Woodlice tend to move faster and change direction more often when air is drier as this increases chances of moving to an area of higher humidity where lose less water so improves chances of survival
Tropism
Growth of a plant in response to a directional stimulus
-Positive tropism- growth towards stimulus
-Negative tropism- growth away from stimulus
Where is IAA produced
shoot tips or root tips (depends of question being asked)
role of IAA
In roots
-inhibts cell elongation
in shoots
-promotes cell elongation
IAA in in shoots (Phototropism)
Cells in tip of shoot produce IAA
IAA conc increases on shaded side
This promotes cell elongation
As shoot bends towards light.
