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Question

Difficulty: MediumEcological Succession

After a severe bushfire destroys a tropical forest ecosystem, fast-growing herbaceous plants and grasses quickly colonize the area by utilizing ash nutrients and seeds preserved within the intact soil. Which of the following best explains why this ecological sequence is classified as secondary succession?

  1. The process originates on a pre-existing soil substrate that already contains organic matter and dormant propagules.Answer
  2. B
    The sequence begins on a bare, uncolonized rock surface devoid of organic matter and previous biological activity.
  3. C
    The pioneer colonizers consist of bryophytes that utilize true vascular tissues to rapidly absorb soil nutrients.
  4. D
    The community bypasses all intermediate seral stages to instantly form a stable climax forest.

Answer

Secondary succession is defined by ecological recolonization that takes place on pre-existing soil containing organic material and dormant seeds following a disturbance.
Secondary succession occurs when a disturbance disrupts an existing ecosystem without eliminating the soil. Because soil, nutrients, and dormant seeds (propagules) remain intact, recolonization proceeds rapidly through pioneer herbs and grasses.

Step-by-Step Solution

1
Identify the key environmental conditions present after the bushfire disturbance.
The fire destroyed vegetation but left intact soil, nutrients in ash, and dormant seeds.
Determining whether a substrate has pre-existing soil is the fundamental criterion for differentiating succession types.
2
Distinguish between primary and secondary succession based on substrate characteristics.
Primary succession starts on bare substrate (e.g., bare rock, volcanic lava, sand dunes) with no soil. Secondary succession starts on established soil after partial destruction.
Existing soil allows faster plant establishment and seed germination.
3
Select the statement that correctly accounts for secondary succession.
The presence of pre-existing soil containing organic matter and propagules defines secondary succession.
This directly aligns with ecological succession definitions.

Key Concept

Distinction between primary and secondary ecological succession based on pre-existing substrate and soil presence.
Estimated Time:1m 0s
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Topics

Ecological Succession

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