CLEP Biology Ecology & Evolutionary Processes 2 — Questions and Answers
Question 1: Which type of symbiosis occurs when one organism benefits and the other is neither helped nor harmed?
- Mutualism
- Parasitism
- Commensalism (Correct answer)
- Competition
Correct answer: Commensalism
Commensalism is a symbiotic relationship where one species benefits and the other experiences no significant effect.
Question 2: The competitive exclusion principle states that two species competing for the same limited resource cannot:
- Coexist in the same habitat indefinitely (Correct answer)
- Evolve different niches over time
- Share a predator
- Hybridize successfully
Correct answer: Coexist in the same habitat indefinitely
Gause's competitive exclusion principle holds that two species occupying the exact same ecological niche cannot stably coexist — one will outcompete and displace the other.
Question 3: In a food web, which trophic level contains the greatest total biomass?
- Tertiary consumers
- Secondary consumers
- Primary consumers
- Primary producers (Correct answer)
Correct answer: Primary producers
Primary producers (plants and other autotrophs) form the base of the energy pyramid and contain the greatest biomass because energy is lost at each trophic level.
Question 4: Which evolutionary mechanism results in the random change of allele frequencies in a small population?
- Natural selection
- Gene flow
- Genetic drift (Correct answer)
- Mutation pressure
Correct answer: Genetic drift
Genetic drift refers to random fluctuations in allele frequencies that are especially pronounced in small populations, potentially causing alleles to be lost or fixed by chance.
Question 5: The concept of 'survival of the fittest' in evolutionary biology most precisely means:
- The physically strongest individuals reproduce most
- Individuals with the highest reproductive success in their environment (Correct answer)
- The fastest organisms avoid predation
- Organisms with the largest body size dominate
Correct answer: Individuals with the highest reproductive success in their environment
Fitness in evolutionary biology refers specifically to an organism's reproductive success — its ability to survive and pass on its genes to the next generation.
Question 6: Which biogeochemical cycle involves the conversion of atmospheric N₂ into ammonia by bacteria?
- Carbon cycle
- Phosphorus cycle
- Nitrogen cycle (Correct answer)
- Sulfur cycle
Correct answer: Nitrogen cycle
Nitrogen fixation, carried out by bacteria such as Rhizobium, converts atmospheric N₂ into ammonia (NH₃), making nitrogen available to plants.
Question 7: Allopatric speciation differs from sympatric speciation primarily because allopatric speciation requires:
- Polyploidy in offspring
- Reproductive isolation without geographic separation
- Geographic separation of populations (Correct answer)
- A sudden change in chromosome number
Correct answer: Geographic separation of populations
Allopatric speciation occurs when a geographic barrier physically separates a population, allowing the two groups to diverge independently until they become reproductively isolated.
CLEP Biology Ecology & Evolutionary Processes 2
Which type of symbiosis occurs when one organism benefits and the other is neither helped nor harmed?