Ecology and Ecosystem Dynamics Quiz

Grade 12 · Science · Quiz

Test your understanding of ecosystems, energy flow, population dynamics, and ecological relationships.

Questions

1. What type of growth curve does a population with unlimited resources display?

   1. S-curve (logistic)
   2. J-curve (exponential)
   3. Plateau curve
   4. Bell curve
   Show answer

   Answer: J-curve (exponential)

   With unlimited resources and no competition, populations grow exponentially — each generation multiplies by a constant factor, producing a J-shaped curve when graphed over time.

2. Producers are the only organisms that can perform photosynthesis.

   Show answer

   Answer: True

   Producers (autotrophs) include plants, algae, and photosynthetic bacteria. They convert light energy into chemical energy, forming the base of all food webs.

3. Species that have a large effect on the ecosystem relative to their abundance are called ___ species.

   Show answer

   Answer: keystone

   Keystone species maintain ecosystem structure. Their removal causes disproportionate collapse — e.g., removal of sea otters allows sea urchins to explode in number and destroy kelp forests.

4. Which process releases CO₂ back into the atmosphere in the carbon cycle?

   1. Photosynthesis
   2. Nitrogen fixation
   3. Cellular respiration
   4. Denitrification
   Show answer

   Answer: Cellular respiration

   Cellular respiration in all living organisms breaks down organic molecules and releases CO₂. Decomposition of dead organisms also returns carbon to the atmosphere.

5. Density-independent limiting factors have stronger effects when population density is higher.

   Show answer

   Answer: False

   Density-INDEPENDENT factors (floods, fires, temperature extremes) affect populations regardless of their size. Density-DEPENDENT factors (disease, predation, competition) intensify as population grows.

6. In a food chain: grass → rabbit → fox → eagle. The fox is a:

   1. Producer
   2. Primary consumer
   3. Secondary consumer
   4. Tertiary consumer
   Show answer

   Answer: Secondary consumer

   In the food chain grass(producer)→rabbit(primary consumer)→fox(secondary consumer)→eagle(tertiary consumer), the fox eats the primary consumer (rabbit), making it a secondary consumer.

7. The maximum population an environment can support is called the ___.

   Show answer

   Answer: carrying capacity

   Carrying capacity (K) is the maximum population size an environment can sustain given available food, water, space, and other resources. Population growth rate approaches zero at K.

8. Denitrification converts nitrates back into nitrogen gas.

   Show answer

   Answer: True

   Denitrifying bacteria in soil convert nitrates (NO₃⁻) and nitrites (NO₂⁻) back into nitrogen gas (N₂), completing the nitrogen cycle and returning nitrogen to the atmosphere.

9. Which type of ecological succession begins on bare rock with no soil?

   1. Secondary succession
   2. Primary succession
   3. Climax succession
   4. Disturbance succession
   Show answer

   Answer: Primary succession

   Primary succession begins on bare substrate (volcanic rock, glacier retreat) with no pre-existing soil. Pioneer species like lichens and mosses begin the soil-building process.

10. An organism that benefits from another without harming or helping it is engaged in:

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

    Answer: Commensalism

    Commensalism is a +/0 relationship where one species benefits and the other is unaffected. Example: birds nesting in trees benefit while the tree is essentially unaffected.

Get a personalized course on Ecology and Ecosystem Dynamics built around your child.