Primary vs. Secondary Succession

What is succession in ecosystems?

• The process of organisms reproducing

• The gradual change in species composition over time

• The immediate response of organisms to a disturbance

• The extinction of species

Answer explanation

Succession in ecosystems refers to the gradual change in species composition over time, as communities evolve and replace one another following disturbances or changes in the environment.

Tags

NGSS.MS-LS2-4

Which of the following is a pioneer species?

• Oak tree

• Lichen

• Deer

• Eagle

Answer explanation

Lichen is a pioneer species because it can colonize bare surfaces and initiate soil formation, making it essential for ecosystem development. In contrast, oak trees, deer, and eagles are not pioneer species.

Primary succession occurs in:

• Areas with existing soil

• Areas that have been disturbed but have soil

• Lifeless areas without soil

• Urban environments

Answer explanation

Primary succession occurs in lifeless areas without soil, such as after a volcanic eruption or glacier retreat, where new ecosystems develop from bare rock or sand, unlike secondary succession which occurs in areas with existing soil.

Secondary succession is typically:

• Slower than primary succession

• Faster than primary succession

• The same speed as primary succession

• Irrelevant to ecosystem recovery

Answer explanation

Secondary succession is faster than primary succession because it occurs in areas where soil and some organisms already exist, allowing for quicker recovery and re-establishment of the ecosystem.

Which of the following events can trigger primary succession?

• A forest fire

• A volcanic eruption

• A hurricane

• Deforestation

Answer explanation

A volcanic eruption can create new land and environments, allowing life to start from bare rock, which is characteristic of primary succession. Other events like forest fires and hurricanes may lead to secondary succession.

What is a climax community?

• A community that is always changing

• A stable and mature ecosystem

• An area with only pioneer species

• A community that has been destroyed

Answer explanation

A climax community is a stable and mature ecosystem that has reached a point of balance and sustainability, unlike areas that are still changing, only have pioneer species, or have been destroyed.

Tags

NGSS.HS-LS4-5

Which of the following is an example of secondary succession?

• A glacier melting

• A lava flow cooling

• A forest regrowing after a fire

• A new island forming

Answer explanation

Secondary succession occurs in areas where a disturbance has destroyed an ecosystem but left the soil intact. A forest regrowing after a fire exemplifies this, as it rebuilds on previously existing soil.

Tags

NGSS.MS-LS2-4

What role do pioneer species play in soil formation?

• They consume all nutrients

• They break down rocks and contribute organic material

• They prevent other species from growing

• They have no effect on soil

Answer explanation

Pioneer species play a crucial role in soil formation by breaking down rocks through physical and chemical processes, and they contribute organic material as they die and decompose, enriching the soil for future plant growth.

After a disturbance, why is secondary succession generally faster?

• More sunlight is available

• Soil is already present

• There is less competition

• Water is more abundant

Answer explanation

Secondary succession is faster because soil is already present, providing nutrients and a substrate for new plants to grow. This contrasts with primary succession, where soil must form from bare rock.

Which of the following is NOT a characteristic of a climax community?

• High biodiversity

• Stability over time

• Constant change

• Mature ecosystems

Answer explanation

A climax community is characterized by high biodiversity, stability over time, and maturity. 'Constant change' contradicts these traits, as climax communities are typically stable and not in a state of constant flux.

Tags

NGSS.MS-LS2-4

NGSS.MS-LS2-5