6A Flashcards
Responding to the Environment
- Organisms increase their chances of survival by responding to changes in their external environment, e.g. moving away/towards places that are too hot/cold)
- Organisms also respond to changes in their internal environment to make sure the conditions are always optimal for their metabolism. Any change in the external or internal environment is called a stimulus
Simple Responses - Tactic response - (Taxis)
Directional movement in response to a stimulus. E.g. woodlice move away from the stimulus of light. They are innate behaviour; They don’t have to be learned
Simple Responses - Kinetic Response - (Kinesis)
Non-Directional (random) movement in response to a stimulus. The intensity of the stimulus affects the response. E.g. Woodlice move slowly and turn less often in high humidity, and when in low humidity, they move faster and turn more often until they move into a new area
What is Positive Tropism?
If an organism moves towards the stimulus
What is Negative Tropism
If an organism moves away from the stimulus
What is Phototropism
Response to light
What is Geotropism?
Response to Gravity
What is a Stimulus?
A change inside or outside an organism that borings about a response in that organism
What is a Receptor?
A structure that detects a stimulus. They communicate with effectors via the nervous system or the hormonal system, or sometimes both
What is an Effector?
A structure that carries out a response. E.g. Muscles, glands, organs and cells.
What is Hydrotropism?
Response to water
Investigating Simple Animal Responses - Light
1 - Construct a choice chamber using a petri dish, a divider and fine mesh
2 - Cover one side of the lid with black paper to make one side of the chamber dark. Then put damp filter paper on both sides of the base to make the humidity constant on both sides of the chamber
3 - Place 10 woodlice on the mesh in the centre and put the lid on
4 - Wait 10 mins and record how many woodlice are on each side
5 - Gently move the woodlice back to the centre and repeat the experiment
6 - To investigate Humidity, place damp filter paper on one side of the chamber and a drying agent on the other. Don’t cover the lid with paper and record the number of woodlice on each side of the chamber after 10 mins
Simple responses are automatic responses to a stimulus, the organism doesn’t ‘choose’ where to move
Order for a simple response
Stimulus, Receptor, Co-ordinator, Effector and Response
What do Baroreceptors detect?
Blood pressure
Neurones (Nerve cells)
It is made up of a complex network of cells called neurones, and the three main types are called:
- Sensory
- Motor
- Relay
What do Sensory Neurones do?
Transmit electrical impulses from receptors to the CNS - the brain and spinal cord
What do Motor Neurones do?
Transmit electrical impulses from the CNS to effectors
What do Relay Neurones do?
Transmit electrical impulses between the sensory and motor neurones
Order of simple response with neurones (The reface arc)
Stimulus, Receptor, Sensory neurone, CNS (Relay), Motor neurone, effectors, response
What are the chemicals called which take information across the gap from one neurone to the next
Neurotransmitters
What are the electrical impulses that are sent along the neurone called (other than nerve impulse)
Action Potentials
What does the Co-ordinator do?
It formulates an appropriate response to a stimulus before sending impulses to an effector
The nervous impulse
When an electrical impulse (Action Potential) reaches the end of the neurone, neurotransmitters (Chemical messengers) are secreted directly onto cells, so the nervous response is localised. The response is short-lived as the neurotransmitters are quickly removed. The impulses are fast, and a response is usually rapid.
What is a simple reflex?
A simple reflex is a rapid, involuntary response to a stimulus. The pathway of communication goes through the spinal cord but not through the conscious parts of the brain, so the response happens automatically. It is protective; to avoid damage to the body.