Survival and response Flashcards
What is a stimlus?
A dectable change in the internal or external environment of an organism that leads a response in the organism
Why is the ability to respond to stimuli a desirable characteristic of life?
Increase the chance of survival of an organism
What is an example of organism survivng to respond to stimlui?
Being able to detect and move away from harmful stimuli
e.g predator/extreme temperatures
or
detect and move towards a source of food
aid survival
They have greater chance of surviving and rasing offspring and pass on their alleles to next generation
There is always a selection pressure favouring organisms with more appropriate responses
What are stimuli detected by?
Receptors
What are receptors specific to?
To one type of stimlus
What does a coordinator formulate?
A suitable response to a stimulus
What does coordination involve?
At a molecular level or involve a large organ like a brain
What is a response produced by?
An effector
What does this response involve?
At a molecular level or involve the behaviour of a whole organism
Why are hormones important?
One means of communication in large multicellular organism
occurs via chemicals - hormones
which is a slow process found in plants and animals
What do animals have other mean of communication instead of hormones?
Their nervous system
Usually have different receptors that control effectors
Each receptor linked with a central coordinator of some type
Act as a switchboard connecting information from each receptor with appropriate effector
What is the sequence?
stimulus - receptor - coordinator - effector - response
What is taxis?
A simple response whose direction is determined by the direction of stimulus
What is a result of a taxis?
A motile organism responds directly to an environmental change by moving its whole body either towards a favourable stimulus or away from an unfavourable one
What are taxis classified as?
According to whether
Towards a stimlus (positive taxis)
Or
Away from stimulus (negative taxis)
also by nature of stimulus
An example of positive phototaxis
Single-celled algae will move towards light (positive phototaxis)
This will increase their chance of survival since, being photosynthetic they require light to manfacture food
An example of negative phototaxis
Earthworms will move away from light
This will increase their chance of survival because it takes them into the soil
They are better able to conserve water, find food and avoid some predators
An example of positive chemotaxis
Some species of bacteria will move towards a region where glucose is highly concentrated (positive chemotaxis)
This will increase their chance of survival because they use glucose as a source of food
What is kinesis?
It is a form of response where the organism does not move towards or away from a stimulus
Instead it changes the speed at which it moves and rate at which it changes direction
e.g humidity and temperature
How is an organism increases its chance to get into a favourable envirnoment?
Move slower/less
Turn less
How does organism increases its chances to get to new area?
From unfavourable envirnoment
Move more faster
Turn faster
An example of kinesis
woodlice
- Woodlice lose water from their bodies in dry condtions
- Move to damp area into dry , move rapidly and change direction more - moving to new area
- This increase their chance of moving back to damp area
- When moving back they slow down and change direction less often - stay in damp area
- Change direction rapidly they still stay in dry area and into a new damp area
- They spend more time in favourable damp conditions and less favourable drier ones
- Prevents from drying out and increase chance of survival
What is tropism?
Growth of part of a plant in response to a directional stimulus
What are the cases of tropisms?
Plant grows towards(positive response)
orgrow away (negative response)
from a stimulus
