Ecological Pyramids & Succession MCQs

1. The pyramid of energy is always:

a) Upright b) Inverted c) Variable d) Sometimes inverted

Correct Answer: a) Upright

Explanation:
The energy pyramid is always upright because energy decreases at each trophic level due to the 10% law of energy transfer. Only about 10% of the energy is transferred to the next level, with the rest being lost as heat during metabolic processes.

2. In a pond ecosystem, the pyramid of biomass is:

a) Upright b) Inverted c) Both a and b d) Neither

Correct Answer: b) Inverted

Explanation:
In aquatic ecosystems like ponds, the pyramid of biomass is often inverted because the biomass of producers (phytoplankton) is less than that of primary consumers (zooplankton). This occurs because phytoplankton have rapid reproduction rates and short lifespans, while zooplankton accumulate more biomass.

3. Biogeochemical cycles involve:

a) Only biotic components b) Only abiotic components c) Nutrient cycling through biotic and abiotic components d) Energy flow only

Correct Answer: c) Nutrient cycling through biotic and abiotic components

Explanation:
Biogeochemical cycles (like carbon, nitrogen, phosphorus cycles) describe how nutrients move between living (biotic) and non-living (abiotic) components of ecosystems. These cycles maintain the balance of essential elements necessary for life through processes like photosynthesis, decomposition, and weathering.

4. Organic nutrients are converted to inorganic forms by:

a) Primary consumers b) Secondary consumers c) Decomposers d) All producers

Correct Answer: c) Decomposers

Explanation:
Decomposers (bacteria and fungi) break down dead organic matter and waste products into simpler inorganic compounds through mineralization. This process releases nutrients like nitrogen, phosphorus, and carbon back into the soil and atmosphere, making them available for reuse by plants.

5. The final stable community in succession is called:

a) Pioneer community b) Intermediate community c) Climax community d) Seral community

Correct Answer: c) Climax community

Explanation:
The climax community represents the final, stable stage of ecological succession that is in equilibrium with the local climate and environment. It maintains its species composition until disturbed by external factors. Examples include mature forests or grasslands that persist for long periods.

6. Primary succession begins on:

a) Degraded forest land b) Bare rock c) Abandoned farmland d) Volcanic ash

Correct Answer: b) Bare rock

Explanation:
Primary succession occurs on previously uncolonized substrates like bare rock, lava flows, or sand dunes where no soil exists initially. Pioneer species (lichens and mosses) weather the rock and begin soil formation, enabling other plants to establish over time.

7. Pioneers in xerarch succession are:

a) Grasses b) Crustose lichens c) Shrubs d) Trees

Correct Answer: b) Crustose lichens

Explanation:
In xerarch succession (dry area succession), crustose lichens are typically the first colonizers. They secrete acids that weather rock surfaces, creating tiny amounts of soil. Their decomposition after death adds organic matter, enabling foliose lichens and mosses to establish next.

8. Ecological succession refers to:

a) Seasonal changes in ecosystems b) Replacement of communities over time c) Migration of animals d) Evolution of species

Correct Answer: b) Replacement of communities over time

Explanation:
Ecological succession is the process of gradual, predictable change in species composition and community structure over time in a given area. It occurs through colonization, competition, and environmental modification until a stable climax community develops.

Ecological Pyramids & Succession MCQs

3. Ecological Pyramids & Nutrient Cycling

4. Ecological Succession

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