14.1 Survival and Response Flashcards
What is a stimulus
A detectable change in the internal or external environment of an organism that leads to a response in the organism
What does responding to stimulus allow an organism to do
Increase survivability, for example being able to detect and move away from harmful stimuli
What does greater survivability from being able to respond to stimulus give organisms a greater chance to do
Raise offspring and pass their alleles to the next generation
What are receptors
Detect stimuli and are specific to one type of stimulus
What are coordinators
They formulate a suitable response to a stimulus. Can be molecular level or involve a large organ such as the brain
What is the role of an effector
To produce a response
What are two examples of communication
- Hormonal system
2. Nervous system
Summarise the sequence of events of a communication system
Stimulus -> receptor -> Coordinator -> Effector -> Response
What are the 3 type of stimuli
- Taxes
- Kineses
- Tropisms
What is a taxis
A taxis is a simple response whose direction is determined by the direction of the stimulus.
It is a change in direction
What is a kinesis
A form or response in which an organism changes the speed at which it moves and the rate at which it changes direction
It is a change in speed
What is a tropism
A tropism is the growth of part of a plant in response to directional stimulus. In almost all cases, the plant grows towards or away from the stimulus
e.g. Plant shoot grows towards light and away from gravity, plant roots grow away from light and towards gravity
