Question

why does secondary succession usually happen faster than primary succession?
there are more animals present
soil is already present
the climate is warmer
there are fewer disturbances
what role do pioneer species play in succession?
they destroy existing plants
they stop succession from continuing
they help create conditions for other organisms to survive
they only live in climax communities

Explanation:

First Question (Why does secondary succession usually happen faster than primary succession?):

To determine why secondary succession is faster, we analyze each option:

• "There are more animals present": Animal presence isn't the main reason for the speed of succession; the key is the state of the environment, especially soil. Eliminate this.
• "Soil is already present": Primary succession starts on bare rock (no soil), so it takes time to form soil. Secondary succession occurs in areas where soil already exists (e.g., after a fire or flood), so plants can grow faster as soil, nutrients, and some organisms are already there. This makes sense.
• "The climate is warmer": Secondary succession doesn't inherently have a warmer climate than primary succession sites. Climate isn't the defining factor for the speed difference. Eliminate this.
• "There are fewer disturbances": Secondary succession often follows a disturbance (like a fire), so disturbances aren't fewer. Eliminate this.

To find the role of pioneer species, we analyze each option:

• "They destroy existing plants": Pioneer species are the first to colonize barren areas (no existing plants in primary succession sites), so they don't destroy existing plants. Eliminate this.
• "They stop succession from continuing": Pioneer species modify the environment (e.g., break down rock, add organic matter) to make it suitable for other species, promoting succession, not stopping it. Eliminate this.
• "They help create conditions for other organisms to survive": Pioneer species (like lichens in primary succession) colonize harsh environments, break down rock, add organic material, and change the environment so that other, less hardy species can later survive. This matches their role.
• "They only live in climax communities": Pioneer species are the first colonizers, while climax communities are the final, stable stage. Pioneer species are replaced as succession progresses and don't live in climax communities. Eliminate this.

Answer:

B. Soil is already present

Second Question (What role do pioneer species play in succession?):