Lecture 13

Question 1

Genes, Environment, and Behavior

Answer 1

• Genes and environment influence phenotypes
• Natural selection shapes behaviors
• Environmental effects on trait values can be described as “plasticity”
• Influence of genes and environment visualized with plots of reaction norm
• Natural selection shapes reaction norm

Question 2

Two questions

Answer 2

• Proximate causes: How/What
• Ultimate causes: Why

Question 3

Phenotypes reflect both genetic and environmental effects

Answer 3

• Z = G+ E + GxE
• Z: phenotype
• G: Genes
• E: Environment
• GxE: Gene by environment interaction

Question 4

Identical twins

Answer 4

• Same genetic make up
• Slight differences in environment lead to variation in traits and behaviors

Question 5

Rover-Sitter Polymorphism

Answer 5

• Yeast spread on agar
  
  • Rovers move around a lot. Sitter don’t move as much
• Phenotype is food related
• In absence of food, rovers and sitters both move more often and for similar distances
• Single major gene(for) underlies rover/sitter polymorphism
• Elements of environment also affect these behaviors

Question 6

Genotype

Answer 6

• Heterozygote phenotype significantly different from sitters but not significantly different from rovers (Rover allele is dominant)
• Homozygote rover: 2.4 avg
• Heterozygote: 1.8 avg
• Homozygote sitter: 0.9 ang

Question 7

Costs and benefits

Answer 7

• Benefit: find more food
• Cost: Expend more energy looking for food

Question 8

Evolution by natural selection requires

Answer 8

• Variation in a trait
• Genetic basis for trait
• Variation in fitness for the trait

Question 9

Can behaviors evolve by natural selection

Answer 9

• Behaviors have lots of variation
• Behaviors have a genetic basis
• Different behaviors have different fitness

Question 10

Environmental effects on foraging

Answer 10

• Adults deprived of food for 4 or 24 hours
• 4 hr deprivation: 36.17 cm for rover, 22.38 for sitter
• 24 hr deprivation: 25.60cm for rover, 16.20cm for sitter

Question 11

Reaction Norms: Visualizing G and E

Answer 11

• Environmental effects on trait values can be described as plasticity
• Influence of genes and environment can be visualized with plots of reaction norm
• Reaction norm described effect of some environmental variable on phenotype of a single genotype

Question 12

Morphological response to predators: Daphnia

Answer 12

• Bigger helmet size in presence of predators
• If there is environmental effect on phenotype of genetically-identical individuals, then there is plasticity

Question 13

Evolution of reaction norms

Answer 13

• Maladaptive: Use of refuge decrease in presence of predator
• Adaptive: Use of refuge increase in presence of predators
• Not plastic: No change

Question 14

Daphnia experiment

Answer 14

• G: Daphnia genotypes from each of 3 lakes
• E: Presence of predators simulated with fish smell
• Look for plasticity of each genotypes do something different when exposed to fish cue compared to when other individuals of same genotypes not exposed

Question 15

Experimental results

Answer 15

• Selection history:
  
  • Many fish: less attracted to light than control
  • Few fish: similar to no fish
  • No fish: As attracted to light as control
• Daphnia don’t know what to do in response to fish