Bio 1500 Test 3 Schul UPDATED ACTUAL
Exam Questions and CORRECT Answers
- Explain how the relationship between phenotype and fitness determines the mode of selection. -
CORRECT ANSWER - Phenotype: observable traits
Fitness: ability to survive & reproduce in an environment
Directional Selection: fitness increases or decreases with trait value
Stabilizing selection: average valued traits have highest fitness
- Explain the outcome of different modes of selection on the mean value of a trait in a
population. - CORRECT ANSWER - Directional selection: mean value skewed towards
traits with highest fitness (longer horns on lizards survive more)
Stabilizing selection: mean value centered, bell-shaped curve (human birth weight)
- Identify several different selection pressures that could influence body size and indicate the
likely direction of phenotypic change in response to the pressure - CORRECT ANSWER -
Sexual selection: competition among males favors large size
Selection for female fecundity (egg/number of offspring): large size
Selection for early reproduction: small size
Limited resource availability: small size
Predation: large size for predators, small size for prey
Locomotion: flight favors small size
Temperature: cold favors large size in mammals
- Describe the insect respiratory system - CORRECT ANSWER - -no blood in insects to
transport oxygen
-individual trachea brings oxygen from environment directly to cells
*spiracles: openings to environment in insects
-oxygen and carbon dioxide travel through diffusion
Exam Questions and CORRECT Answers
- Explain how the relationship between phenotype and fitness determines the mode of selection. -
CORRECT ANSWER - Phenotype: observable traits
Fitness: ability to survive & reproduce in an environment
Directional Selection: fitness increases or decreases with trait value
Stabilizing selection: average valued traits have highest fitness
- Explain the outcome of different modes of selection on the mean value of a trait in a
population. - CORRECT ANSWER - Directional selection: mean value skewed towards
traits with highest fitness (longer horns on lizards survive more)
Stabilizing selection: mean value centered, bell-shaped curve (human birth weight)
- Identify several different selection pressures that could influence body size and indicate the
likely direction of phenotypic change in response to the pressure - CORRECT ANSWER -
Sexual selection: competition among males favors large size
Selection for female fecundity (egg/number of offspring): large size
Selection for early reproduction: small size
Limited resource availability: small size
Predation: large size for predators, small size for prey
Locomotion: flight favors small size
Temperature: cold favors large size in mammals
- Describe the insect respiratory system - CORRECT ANSWER - -no blood in insects to
transport oxygen
-individual trachea brings oxygen from environment directly to cells
*spiracles: openings to environment in insects
-oxygen and carbon dioxide travel through diffusion
