1. Neurobiology & Behaviour
HL & SL Option E

2. Stimulus & Response
E.1.1. Define the terms stimulus, response, and reflex in the context of animal behaviour.

3. Stimulus, response, and reflex
Stimulus (pl. stimuli)
A change in external or internal environment that is detected by a receptor and elicits a response
Response
Is a reaction to a stimulus
Reflex
Is a rapid, unconscious response
e.g. - the response to pain

4. Video

5. Response of animals to pain stimuli
E.1.2 Explain the role of receptors, sensory neurones, relay neurones, motor neurones, synapses and effectors in the response of animal to stimuli

7. Receptors receive the stimulus Receptors
Pain Reflex Arc
Receptors receive the stimulus
Pain, heat, pressure, chemicals
Receptors
Generate a nerve impulse in the sensory neurons
Sensory neurons carry the impulse toward the spinal cord
The axons of the sensory neuron enters the spinal cord

8. Pain Reflex Arc
The axon of the sensory neuron enters the spinal cord in the dorsal root
It sends a chemical message across a synapse to a relay neuron (interneuron)
Synapse – functional connections between neurons or between neurons and other types of cells.
Relay neuron (interneuron) is located in the gray matter
The motor neuron is located in the ventral root of the spinal cord

9. Pain Reflex Arc
It carries the impulse to an effector
An effector is an organ that performs the response
Effectors are muscles or glands
A reflex is an automatic response following a sensory stimulus. It is not under conscious control and is therefore involuntary (it does not involve the human brain.)

10. E.1.3 Draw and label a reflex arc for a pain withdrawal reflex, including the spinal cord and its spinal nerves, relay neuron, motor neuron, and effector

12. E.1.4 Explain how animal responses can be affected by natural selection, using two examples

13. http://msjensen. cehd. umn

14. Effects of Natural Selection
Animal behaviour is much more than just single reflex arcs
Behavioural changes may be so extreme that a new species is formed
Review – Black Peppered Moths

15. Migration in European Blackcaps
Small warblers
Migrate between Germany & Spain
Breed in Germany in spring
Spend the winter in Spain

16. Migration in European Blackcaps
50 years ago – some blackcap warblers came to UK for winter
UK blackcaps left to go back to Germany 10 days earlier than the Spanish blackcaps
The earlier the birds arrived in Germany, the more choice of territory they had; the more eggs they laid
UK warblers have an advantage

17. Video

18. Migration in European Blackcaps - experiment
Eggs collected from UK parent
Eggs collected from Spanish parents
Young reared without parents
All birds in study migrated in the same direction that their parents had gone
Supports the hypothesis – blackcaps are genetically programmed to fly in a certain direction
Change in migration patterns may cause new species

19. Sockeye Salmon
Video clip

20. Sockeye salmon were introduced into Lake Washington
Some migrated to Lake Cedar
River flows quickly – lake is deep & quiet
Different aquatic environments

21. Sockeye Salmon – Lake Washington
13 generations of salmon over 60 years
River & lake salmon do NOT interbreed
2 different breeding methods
Lake salmon spawn on the beach, females lay eggs in the sand
Males have heavy bodies & are inefficient at navigating fast currents in the river

22. Sockeye Salmon – Cedar Lake
Thinner & narrower bodies
Females bury their eggs deep in the sandy river bottom – not washed away
Fish hatched in the river had little success trying to spawn on the beach

23. Comparison of the Sockeye Salmon
Variations in the 2 populations were selected for by the 2 different environments
Original population diverged into 2 different breeding populations.
The lake conditions favour one set of traits and the river conditions favour another set of traits
Sockeye salmon are now 2 genetically distinct populations