Neurobiology/Behavior

By: Anam SaeedSandya KumarKendra Wang

E.1.1. Define these terms in the context of animal behavior.

• Stimulus• Response • Reflex

Stimulus● Stimulus (pl. stimuli) - Change in the environment (internal or

external) detected by a receptor.○ E.g. sunrise, a sound, increase in blood sugar.

● External stimuli refers to touch, pressure, heat. Internal stimuli refers to the stimuli being produced by body components.

● Stimulus is capable of evoking response in an organism

Response• Response - Change in organism due to the stimuli; it is an

action or movement that occurs due to stimuli ● Instincts are automatic behavioral responses to stimuli. This is

known as FAPs (Fixed Actions Patterns) ○ FAPs and Instincts are the results of natural selection. The

most effective automatic responses to stimuli give the individual a survival and/or reproductive advantage, and so they are passed on.

● Reflex - A type of response that is rapid and unconscious e.g. the response to pain

● Stimulus is a detectable change in the internal and external environment, and when applied to sensory receptors (e.g. sensory neurons) it is what causes your reflex.

● Reflexes are the product of natural selection. Rapid and unconscious responses allow for danger avoidance with minimal harm to the organism (Pain is a good thing!)○ The pain reflex is moderated by the spinal cord rather than the

brain -- shorter paths, faster responses and no conscious decisions needed.

Reflex

Natural selection requires:● a change in the environment● various phenotypes ● a genetic basis to this variation

If the organism is evolving then we might expect to observe a change in the frequency of heritable characteristics

E.1.4. Explain how animal responses can be affected by natural selection.

Phenotypic variations is in the direction of migration (behavior)

Normal/Original FAP: ● Chicks hatch and fly Southwest to

Spain for the winter (migration to avoid harsh winters)

Alternate behavior:● Some flew Northwest to the UK

where birdfeeders provide easy sources of food

Example 1: European Blackcap (Sylvia atricapilla) migration patterns

Advantage:● Shorter flight distances and easy supply of food from bird enthusiasts

allow blackcaps to return to German breeding sites ahead of Spanish migrants and be more reproductively successful

Natural Selection:● Genes for Northwest migration passed on and proliferate in population

Example 1 cont.

Experimental Evidence:● Eggs are taken from both populations of Blackcap. Northwest

hatchlings flew Northwest, even though there were no parents to follow - likewise with the chicks of Southwest migrators - strong suggestion of genetic basis for direction in migration

Conclusion:● Genetic and morphological differences are now apparent between the

two populations.

Example 1 cont.

Normal/Original FAP:

• Coastal snakes diet includes amphibians and the Banana slug (Ariolimus californicus)

Alternate behavior:

• Inland snakes diet main component frog, leach and fish (slug is absent)

Example 2: Prey preference in the Garter Snake (Thamnophis elegans) of California

Natural Selection:• The difference between the coastal and inland Garter snake is genetic,

the gene allows the snake to detect the molecule that is the slugs ‘smell’. In other words the sense of smell of the snakes is different.

• The evolution of ‘slug smelling’ in coastal species is an adaptation made in those regions. Those individuals with the ‘slug smelling’ gene found more or better food than ‘non smellers’ , through better more successful reproduction this gene become more frequent in the population.

Example 2 cont.

Experiment Evidence:● In an experiment pregnant snakes from the two regions have been collected.

Inland and Coastal animals are isolated from each other.● The hatchlings are offered Banana slug food over a 10 day period● Offsprings of Coastal ate 60% of the Banana Slugs while the Inland ate 20% of

the Banana Slugs.

Conclusion:● Coastal Garter Snake eat more Banana slugs than Inland Garter snakes● Behaviour differences are genetically based● Two populations have diverged due to a difference in behaviour (not speciation,

yet).

Example 2 cont.

Success of an organism can be measured by:• Quality of the offspring• Capacity to breed (Reproductive fitness)

Through natural selection, the features improving a male's chances of successfully competing with other males for the best mate (mate selection) will become more dominant.

E.6.5. Explain how mate selection can lead to exaggerated traits.

Exaggerated traits, called “ornaments”,• Likely to attract female attention• Promote successful reproduction• These traits will be selected for, although they may increase

predator attention and diminish the survival prospects of the individual.

- The evolution of these traits in a particular gender has led to the marked sexual dimorphism of certain species.

E.6.5.

Feathers of the peacock• Male peacock displays and on the

basis of a ‘good’ display, he will be chosen by the rather dull female peacock for reproduction.

• This feather ‘display’ is regarded as an ‘exaggerated trait’, where such traits are believed to have evolved by sexual selection.

Example of mate selection leading to exaggerated traits

Animals show behaviours that follow rhythmical variation, for instance,

• Diurnal (daily) cycles• Lunar cycles (monthly)• Seasonal changes

E.6.6. State that animals show rhythmical variations in activity.

• Grizzly Bearso Grizzly bears tend to hibernate during the winter.o They undergo a period of inactivity due to metabolic depression.o Hibernation conserves energy and is therefore of value during winter months when

food availability is low and cost of hunting is high.

• Coralso In many species of coral, males and females release their gametes at the exact

same time of the year (mass spawning).o The advantage of such behaviour is that it increases the chances of the male and

female gametes undergoing successful fertilisation.o Spawning may be triggered by a number of factors, including temperature (seasonal)

and moonlight (lunar).

E.6.7. Outline 2 examples illustrating the adaptive value of rhythmical behavior patterns.

Activity #1:Imagine touching the hot surface of a stove or the metal part of the seatbelt

in a car during the middle of June. Now explain each step of how you reflexively took your hand away. Include words such as stimulus, response, and reflex.

Activity # 2:JeOpArDyActivity # 3 (if there is time):and BINGO was his name O!

ACTIVITIES