Genes and Behavior

Question 1

what is evolution

Answer 1

genetic change in a population

change in allele frequencies over time

Question 2

what are the mechanisms that cause evolution?

Answer 2

• natural selection
• migration between populations (gene flow)
• random processes (genetic drift)

Question 3

are all behaviors adaptive? (change in allele frequencies over time)

Answer 3

nope
- Could have evolved due to migration or drift
- Could have evolved due to different selection
pressures in the past.
Ex. slow (i.e., efficient) metabolism in humans

Question 4

Evolution by natural selection

Answer 4

1. Trait (e.g., behavior) varies among
   individuals in the population.
2. The behavior is heritable (genetic basis).
3. Individuals exhibiting behavior have higher
   fitness (greater reproductive success, more
   offspring) than those without behavior.
   (Behavioral trait evolves in the population.)

Question 5

How do genes influence behavior?

Answer 5

• Proteins (ex. hormones) involved in molecular,
biochemical, or neuronal cascades that
influence behavior.
• Most phenotypes (including behaviors) are
the result of many genes & the environment.

Question 6

does phenotypic plasticity change in individuals or populations

Answer 6

changes in individuals

plasticity: non-learning

Question 7

Innate, fixed behaviors:

Answer 7

genetically hard-wired;
can be performed in response to a cue without
prior experience

Question 8

Behavioral plasticity

Answer 8

The ability of one individual (or a single genotype) to exhibit different behaviors when exposed to different environmental
conditions.

Question 9

Contextual plasticity (non-learning):

Answer 9

external stimuli in a given context activate neural and hormonal mechanisms or pathways which already exist inside the organism.

Question 10

Learning:

Answer 10

behaviors develop as a result of experience

• Individual learning
• Social learning

Question 11

Phenotypic plasticity

Answer 11

The ability of one individual (or a single genotype) to exhibit different phenotypes when exposed to different environmental conditions.
Ex: Daphnia magna when fish induced they moved away from the light (contextual plasticity)

Question 12

Habituation:

Answer 12

animal stops responding to a

stimulus, or cue, after repeated exposure

Question 13

Operant conditioning:

Answer 13

results when a behavior 
induces a punishment or reward—decreases or 
increases display of behavior 
Ex: learned prey odor 
avoidance in predatory sea 
slugs noboa & gillette

Question 14

Social learning

Answer 14

Animals learn by observation of, or interaction

with, another individual(s)

Question 15

In order for natural selection to result in an

evolutionary response

Answer 15

variation in

behavioral trait must have a genetic basis.

Question 16

How can you determine if a behavior is

caused by genes?

Answer 16

Selective Breeding Experiments

Question 17

Selective Breeding Experiment

Answer 17

Via controlled breeding, artificially select for certain behaviors; see if trait evolves.
Ex. Cade (1981) Science 212:563-564
• Field crickets (Gryllus integer)
• Two types of mating strategies
– Some call to attract females
– Others wait silently to intercept females (satellites)
• Cade selected for males that 1) called a lot and 2) those that called rarely

Question 18

Selective Breeding Experiment results

Answer 18

Demonstrated that
calling behavior has
some genetic basis

Question 19

Common Garden (Transplant) Experiments

Answer 19

– Used to determine if behaviors are genetic vs.
environmentally-induced (plastic)
– Raise individuals from populations with different
behaviors in a common environment (ex. lab).
– If they display different behaviors = genetic.

Question 20

Example of Common Garden (Transplant) Experiments

Answer 20

Ex. Robinson et al. (2008) American Naturalist
Observed differences in egg incubation periods for tropical vs. temperate house wrens (10% longer in tropics).
- Eggs collected from Panama, Illinois
- Raised in common lab environment 
(incubation chamber)
- Incubation period measured
Demonstrated that egg incubation 
period has genetic basis

Question 21

Cross-fostering (Reciprocal transplant)

Experiments

Answer 21

– Used to determine whether behaviors are innate vs. learned (e.g., from parents)
– Start with parents that display different behaviors
– Do reciprocal transplant with young offspring
– Observe offspring phenotype

Question 22

Cross-breeding Experimen

Answer 22

– Start with populations that have different behaviors
– Mate individuals from different populations
– Observe offspring phenotype