Ecology Review MultipleChoice Questions & Answers

1. Which of the following best defines an ecosystem?

1. A group of individuals of the same species living in the same area.
2. The physical environment only, without any living organisms.
3. A community of organisms interacting with their abiotic environment.
4. The total number of different species in a region.

Answer: C

An ecosystem includes both biotic (living) and abiotic (nonliving) components and the interactions between them.

2. Primary productivity is primarily controlled by:

1. Soil texture.
2. Sunlight availability.
3. Predator abundance.
4. Wind speed.

Answer: B

Photosynthetic organisms need light energy; thus, sunlight is the main limiting factor for primary production.

3. In a typical food chain, approximately what percentage of energy is transferred from one trophic level to the next?

1. 90%
2. 50%
3. 25%
4. 10%

Answer: D

Only about 10% of energy is passed on; the rest is lost as heat, waste, or used for metabolism.

4. Which of the following organisms is a primary consumer?

1. Hawk
2. Grasshopper
3. Decomposer fungus
4. Oak tree

Answer: B

Grasshoppers feed on producers (plants) and are therefore herbivores primary consumers.

5. In the nitrogen cycle, the process that converts atmospheric N into biologically usable NH is called:

1. Denitrification
2. Nitrification
3. Ammonification
4. Biological nitrogen fixation

Answer: D

Nitrogenfixing bacteria (e.g., Rhizobium) transform N into ammonia (NH), making nitrogen available to plants.

6. Which reservoir holds the largest amount of carbon on Earth?

1. Atmosphere
2. Oceans
3. Fossil fuels
4. Vegetation

Answer: B

The oceans store about 38,000Gt of carbon, far exceeding atmospheric and terrestrial pools.

7. A population that grows continuously at a constant rate per individual is described by:

1. Logistic growth
2. Exponential growth
3. Linear growth
4. Densityindependent growth

Answer: B

Exponential (or geometrical) growth occurs when the percapita birth rate exceeds death rate and resources are unlimited.

8. In the logistic growth model, the carrying capacity (K) represents:

1. The maximum possible population size under ideal conditions.
2. The current number of individuals in a population.
3. The rate at which individuals reproduce.
4. The amount of food available per individual.

Answer: A

K is the upper limit that the environment can sustainably support.

9. Which interaction occurs when two species benefit from each other?

1. Competition
2. Parasitism
3. Mutualism
4. Commensalism

Answer: C

Mutualism provides a positive effect to both participants (e.g., pollinators and flowering plants).

10. When one species preys upon another, the effect on the preys population is typically:

1. Positive densitydependence
2. Negative densitydependence
3. Neutral
4. Densityindependent

Answer: B

Higher prey density often leads to greater predator success, producing a negative feedback on the prey population.

11. The edge effect most commonly refers to:

1. Increased predation near the boundary of habitats.
2. The influence of habitat edges on species composition and microclimate.
3. Genetic drift in small populations.
4. Loss of nutrients from soil erosion.

Answer: B

Edges alter light, temperature, and humidity, often creating conditions different from interior habitats.

12. Which of the following is a primary goal of ecological restoration?

1. Increase the aesthetic appeal of a landscape.
2. Reestablish natural processes and biodiversity.
3. Introduce exotic species for economic profit.
4. Maximize timber yield.

Answer: B

Restoration seeks to recover ecosystem structure, function, and diversity that have been degraded.