Biology Test Biology Ecology and Evolution 3 — Questions and Answers
Question 1: What is the primary source of energy for most ecosystems on Earth?
- Chemical energy from decomposers
- Thermal energy from the Earth's core
- Solar energy captured by photosynthesis (Correct answer)
- Kinetic energy from wind and water
Correct answer: Solar energy captured by photosynthesis
Photosynthetic organisms (plants, algae, cyanobacteria) convert solar energy into chemical energy, forming the energetic foundation of most food webs.
Question 2: Which type of speciation occurs when a physical barrier geographically separates a population?
- Sympatric speciation
- Parapatric speciation
- Allopatric speciation (Correct answer)
- Peripatric speciation
Correct answer: Allopatric speciation
Allopatric speciation occurs when a population is divided by a geographic barrier, preventing gene flow and allowing the groups to diverge into separate species.
Question 3: In a food web, what is the effect of removing a keystone predator?
- Species diversity increases across all trophic levels
- The prey population explodes, destabilizing the ecosystem (Correct answer)
- Primary producers are unaffected
- Decomposer activity decreases
Correct answer: The prey population explodes, destabilizing the ecosystem
Without the keystone predator, prey populations grow unchecked (trophic cascade), often overgrazing or outcompeting other species and reducing biodiversity.
Question 4: Which biogeochemical cycle involves bacteria converting atmospheric nitrogen into forms usable by plants?
- Carbon cycle
- Water cycle
- Phosphorus cycle
- Nitrogen cycle (Correct answer)
Correct answer: Nitrogen cycle
In the nitrogen cycle, nitrogen-fixing bacteria convert atmospheric N₂ into ammonia (NH₃), which plants can absorb and use to build proteins.
Question 5: What does 'r-selected' reproductive strategy describe in ecology?
- Species that invest heavily in few offspring with high parental care
- Species that produce many offspring with little parental investment (Correct answer)
- Species adapted to stable, resource-rich environments
- Species at the top of the food chain
Correct answer: Species that produce many offspring with little parental investment
r-selected species maximize reproductive rate by producing many offspring with minimal parental care, thriving in unstable or unpredictable environments.
Question 6: What evolutionary evidence is provided by the existence of vestigial structures?
- Organisms create new structures as needed
- Species share common ancestry with ancestors that used those structures (Correct answer)
- Convergent evolution produced similar traits independently
- Genetic mutations are always beneficial
Correct answer: Species share common ancestry with ancestors that used those structures
Vestigial structures are reduced, functionless remnants of structures that were functional in ancestors, indicating shared evolutionary history.
Question 7: Which process transfers energy and matter from dead organisms back to the ecosystem?
- Predation
- Competition
- Decomposition (Correct answer)
- Mutualism
Correct answer: Decomposition
Decomposers (fungi and bacteria) break down dead organic matter, recycling nutrients back into the soil and atmosphere for use by producers.
Biology Test Biology Ecology and Evolution 3
What is the primary source of energy for most ecosystems on Earth?