Station 15Ecological Succession

Reporting Category 5Interdependence Within Environmental Systems

Essential Question – Bell Ringer• How do the processes and events that occur

within an ecosystem affect the species and populations of organisms that live in that ecosystem?

The processes and events that occur within an ecosystem change the conditions found in the ecosystem. For example, as soil develops in a primary succession stage, the conditions become more favorable for a different species to migrate in and inhabit the ecosystem. The new species would not have been able to exist in the ecosystem before the pioneer species that first inhabited the ecosystem set the stage for new species’ survival.

Pre-Review Question

True/False

An Ecological Succession is the natural the process by which ecosystems change and develop over time.

TRUE

Pre-Review Question

What are the stages that occur in an ecological succession?

Primary

Secondary (Young then Old)

Climax

Pre-Review Question

Determine if the following organisms are likely to be among the first to inhabit an ecosystem after a volcanic eruption?

A.Moss and Lichen?

B.Heterotrophs?

C.Carnivores?

D.Autotrophs?

Yes

No

No

Yes

Lab Activities

• You will now go to the lab and complete the activities for today’s topics.

Place each card in the appropriate position on the Ecological Succession Model sheet. Read each card and make sure you know which autotrophs and which heterotrophs exist in each succession. Continue until all cards are placed on the model.Copy the chart in your journal.

Discuss with your partner:Why are there no heterotrophs in the primary succession stage?

There are no heterotrophs inhabiting the ecosystem in the primary succession stage because the autotrophs are not able to support them until the end of the primary succession stage, when the soil conditions are better suited to support a more diverse species of plants.

Discuss with your partner: How do the processes and events that occur during the primary succession stage result in the appearance of more diverse populations of autotrophs in the first stage of secondary succession?

In the primary succession stage, the process of chemical weathering and the event of lichen growth cause rocks to break down, forming soil. As some of the lichens die, they add organic material to the broken down rock. This early stage of soil can now support other autotrophs that in turn attract the kinds of heterotrophs that feed on them. This adds to the diversity of the ecosystem.

Discuss with your partner:What effect does a more diverse population of autotrophs in both stages of secondary succession have on the appearance of heterotrophs?

A more diverse population of autotrophs increases the diversity of heterotrophs that depend on the diversity of autotrophs present in the ecosystem.

Discuss with your partner:What conditions exist in a climax community that support the statement “a climax community is in a steady state of ecological equilibrium”?

A climax community is one that is mature, self-sustaining, and stable. The biotic and abiotic conditions are altered and stabilized to such levels that they support the entire community. This will continue until an outside disturbance occurs, shifting the community from the climax stage.

Discuss with your partner:What effects would the natural disturbances you chose have on the diversity of organisms in the ecosystem if it were in the young stage of secondary succession?Answers will vary.

For example, a volcanic eruption would destroy all living organisms and the soil, reverting the ecosystem back to the primary succession stage. However, if the disaster is the result of a flood, the soil may not be completely removed and the ecosystem would not regress to the primary succession stage.

Discuss with your partner: What are some kinds of disturbances or disasters that are caused by humans? Select one and discuss the effects it could have on the diversity of the species in the ecosystem affected by this event.Answers will vary.

Key points to consider:

• Is the disturbance indeed caused by human actions such as over-grazing of animals, nuclear disaster, deforestation, or growth of human populations?

• Did the student clearly consider the effects on the ecosystem in terms of both the biotic and abiotic factors?

• Species living in an ecosystem gradually change over time, as do the physical and chemical environments within that ecosystem.

• Succession takes place because organisms interact with one another in an ecosystem.

• Left undisturbed, succession follows predictable stages: primary, secondary, and climax communities.

• Autotrophs are the first pioneer species to inhabit an ecosystem in the primary stage; they create conditions that may be favorable to other autotrophs.

• Heterotrophs follow autotrophs in the stages of succession—first herbivore heterotrophs and then carnivores and omnivores.

• An ecosystem reaches stability when it becomes a climax community. In this stage it is stable, mature, self-sustaining, and has reached an ecological equilibrium.

I need to remember………

At which point in an ecological succession would the following occur?

Seeds brought by wind and other animals have a place to grow.

No heterotrophic organisms inhabit the ecosystem.

Large trees become the dominant plant species.

Post Review Question

Secondary

Primary

Climax

Post-Review Question

Why are there not carnivores in an ecosystem going through a primary succession?

Because there is nothing for them to eat

Post-Review Question

Which two words could describe the migration of species into a new habitat.

A. Exitation

B.Colonization

C.Emigration

D.Immigration

Post-Review QuestionLook at the natural disasters or human disruptions below and determine to which stage they would send and ecosystem…

Flood -

Fire -

Volcanic Erupuption -

Deforestation -

Pollution -

Hurricane -

Secondary

Primary

Secondary

Secondary

Secondary

Secondary