Survival and response Flashcards
Stimulus
a detectable change in environment
these can be either internal or external
simple reaction pathway
stimulus—>receptor—>coordinator—>effector—>rsponse
Why do organisms need to respond to changes in their environment
Increased survival and reproduction by:
- Avoiding harmful environments, competition and predators
- Keep in a favourable environment
- Grow towards/away from stimuli
- Dispersing to find new mates
Behaviour patterns points
- instinctive behaviour is an innate response to stimuli
- innate behaviour is genetically determined, it is not learned
- members of species which inherit alleles for a particular behaviour will produce the same response to a particular stimulus
Types of simple responses to stimuli
Kinesis
Taxes
Reflex action
Kinesis response to stimuli
- random
- behaviour pattern where an animal responds to a change in simulus by increasing or decreasing activity
- it is change in rate of movements
Taxes response to stimuli
- directional
- organism moves either towards or away from a stimulus
- the directional of the response is related to the direction of the stimulus
two types of taxes
positive taxes
negative taxes
example for taxes
earthworms move away from light
negative phototaxes
more chance of survival as move into soil
more likely to find food
more likely to avoid predators
less likely to dehydrate
What is a reflex action
a certain stimulus that produces a specific short lived response
How would you describe reflex actions
-rapid
-unlearnt
-automatic
How do reflex actions help organisms
- protect against damage to the body tissues
- help escape from predators
- enable homeostatic control
- finding food, mates or suitable environmental conditions
what is in the reflex arc
receptor
sensory neurone
relay neurone
motor neurone
effector
what is a tropism
the direction of growth can be towards and away from the stimulus
types of tropism
positive or negative tropism
what is an example of tropism
positive tropism
plant shoots grow towards light
what are specific growth factors
-specific growth factors are synthesised in cells located throughout the plant
-they then diffuse from growing regions to other tissues
-e.g. Auxins IAA
IAA process in the shoots
-promotes cell elongation
-IAA synthesised in shoot tips
-IAA diffuses into growing region
-Light causes movement of IAA from light side to shaded side
-Higher conc. IAA on shaded side
-Causes directional growth as there is greater cell elongation on shaded side
-Shaded side grows faster and causes shoot to bend towards the light
IAA process in the roots
-inhibits cell elongation
-IAA synthesised in root tips
-IAA diffuses into growing region
-Light causes movement of IAA from light side to shaded side towards gravity
-Higher conc. IAA on shaded side
-Cell elongation on shaded side
-Results in directional growth away from light and towards gravity
