Biology Test Biology Ecology & Environmental Interactions 2 — Questions and Answers
Question 1: Which of the following best describes a keystone species?
- A species with the largest population in an ecosystem
- A species whose removal causes dramatic ecosystem change disproportionate to its abundance (Correct answer)
- A species at the top of the food chain
- A species that produces the most biomass
Correct answer: A species whose removal causes dramatic ecosystem change disproportionate to its abundance
Keystone species have outsized ecological roles; their removal triggers cascading changes far beyond what their population size would suggest.
Question 2: In a food web, secondary consumers are organisms that
- Produce energy through photosynthesis
- Eat only plants
- Eat primary consumers (Correct answer)
- Decompose dead organic matter
Correct answer: Eat primary consumers
Secondary consumers occupy the third trophic level, feeding on primary consumers (herbivores).
Question 3: The nitrogen cycle is critical to ecosystems primarily because nitrogen is
- A greenhouse gas that traps heat
- An essential component of amino acids and nucleic acids (Correct answer)
- Required for photosynthesis as an electron donor
- The primary source of energy for decomposers
Correct answer: An essential component of amino acids and nucleic acids
Nitrogen is a core element of proteins and DNA, making its cycling through ecosystems vital for all living organisms.
Question 4: Which term describes the gradual process by which a bare rock surface develops into a mature forest community?
- Secondary succession
- Primary succession (Correct answer)
- Ecological regression
- Eutrophication
Correct answer: Primary succession
Primary succession begins on lifeless substrates like bare rock where no soil exists, starting with pioneer species like lichens.
Question 5: An organism that benefits from a relationship while its host is neither helped nor harmed is engaged in
- Mutualism
- Predation
- Commensalism (Correct answer)
- Parasitism
Correct answer: Commensalism
Commensalism is a +/0 relationship where one species benefits and the other experiences no significant effect.
Question 6: What happens to energy as it moves from one trophic level to the next in an ecosystem?
- It doubles due to metabolic processes
- About 90% is lost, primarily as heat (Correct answer)
- It is fully conserved and transferred completely
- It increases because higher trophic organisms are more efficient
Correct answer: About 90% is lost, primarily as heat
The 10% rule states that roughly 10% of energy is passed to the next trophic level; the rest is lost as heat through cellular respiration.
Question 7: Which biome is characterized by permafrost, extremely low temperatures, and low biodiversity dominated by mosses and lichens?
- Taiga (boreal forest)
- Temperate grassland
- Tundra (Correct answer)
- Chaparral
Correct answer: Tundra
The tundra biome features permanently frozen subsoil (permafrost), a short growing season, and vegetation limited to low-growing plants.
Biology Test Biology Ecology & Environmental Interactions 2
Which of the following best describes a keystone species?