Homework worksheet on ecological succession featuring a diagram of ecosystem development over time.

Let's go through each question in the Ecological Succession homework and solve them step by step with explanations.

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1. Biomass is the amount of living material present in an environment. Biodiversity refers to the variety of living things that are present in an ecosystem. Which of the following would you expect to occur over time as ecological succession moves forward?

Answer: A) increases in both biomass and biodiversity

✔ Explanation:
As ecological succession progresses (from barren rock → lichens → grasses → shrubs → softwoods → hardwoods), more complex plant communities develop. This leads to:
- Increased biomass: More plants grow, store more energy, and produce more organic matter.
- Increased biodiversity: More species can survive as habitats become more complex and stable (e.g., insects, birds, mammals).

So, both biomass and biodiversity increase over time.

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2. Which of the following animal niches will be filled first as an ecosystem begins the stages of ecological succession?

Answer: C) herbivore

✔ Explanation:
In early succession, the first organisms are pioneer species like lichens, mosses, and grasses. Once these plants establish, herbivores (plant-eating animals) can move in and feed on them.

- Carnivores and apex predators need herbivores to eat — so they come later.
- Scavengers may appear after some death, but only after some life exists.

Thus, herbivores are among the first animals to arrive.

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3. New ground begins as barren rock. This rock is covered in lichens and mosses, and eventually soil forms. Which two processes are most responsible for forming this soil at the beginning of ecological succession?

Answer: C) Weathering and Decomposition

✔ Explanation:
- Weathering: Physical, chemical, and biological breakdown of rock into smaller particles. Lichens secrete acids that chemically weather the rock.
- Decomposition: When lichens and mosses die, their remains decompose and mix with weathered rock, forming soil.

Other options:
- Subduction/Deformation: geological processes that form mountains, not soil.
- Transpiration/Precipitation: water cycle processes, not directly soil-forming.
- Crystallization/Condensation: mineral formation or water vapor processes.

So, weathering and decomposition are key.

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4. The diagram above shows how one community of organisms replaces another until which of the following is reached?

Answer: D) climax community

✔ Explanation:
Ecological succession ends when a climax community is reached — a stable, self-sustaining ecosystem where species composition changes very slowly. In this case, it’s the hardwood forest, which represents the final stage.

- Pioneer community: early stage (lichens, mosses).
- Ecological pyramid: a model of energy flow, not a stage.
- Marine biome: unrelated; this is terrestrial succession.

So, the answer is climax community.

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5. Lava from a volcano cools and becomes new, barren land. If this land is completely barren, then it would contain –

Answer: A) only abiotic factors

✔ Explanation:
- Abiotic factors = non-living components (rock, lava, sunlight, temperature, water, etc.)
- Biotic factors = living organisms (plants, animals, microbes)

If the land is completely barren, there are no living organisms yet — so no biotic factors.

Only abiotic factors exist initially.

So, only abiotic factors are present.

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6. The diversity of animals increases alongside plants because larger plant communities provide

Answer: C) more chemical energy in the food chain

✔ Explanation:
Plants are primary producers. As plant communities grow more complex:
- They capture more solar energy via photosynthesis.
- This provides more chemical energy (in the form of glucose) that flows up the food chain.
- More energy supports more species (herbivores, carnivores, etc.).

Other options:
- A: Defense from parasites — not a main reason.
- B: More sunlight warming the ecosystem — not relevant; sunlight is constant.
- D: Fewer places to hide — false; more plants = more hiding spots.

So, more chemical energy allows greater animal diversity.

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✔ Final Answers:

| Question | Answer |
|--------|--------|
| 1 | A |
| 2 | C |
| 3 | C |
| 4 | D |
| 5 | A |
| 6 | C |

Let me know if you'd like a printable version or help understanding any part further!