Notes 4.3 - Ecological Succession

What is a relatively new idea in ecology regarding ecosystems?

• That ecosystems are always stable and unchanging

• That dramatic, periodic change can be a part of normal ecosystems

• That ecosystems never experience change

• That ecosystems are not affected by external factors

What was previously considered the optimal state of ecosystems?

• Instability

• Change

• Stability

• Diversity

How has our understanding of ecological communities changed with more observations and studies?

• We now believe communities are always stable

• We have learned that communities can be dynamic and experience dramatic changes over time

• We think communities never change

• We believe communities are unaffected by external factors

According to F. E. Clements, the process of community development most closely resembles which of the following?

• The maturation of an organism

• The growth of a plant

• The migration of animals

• The change of seasons

Which of the following best describes the concept of a climax community?

• The final and longest lasting stage in community development

• The first stage of community development

• A temporary stage in the life of a community

• A stage where all species are eliminated

Which type of succession occurs when bare land is colonized by living organisms where none lived before?

• Secondary succession

• Tertiary succession

• Primary succession

• Climax succession

Compare and contrast primary and secondary succession in terms of their starting conditions and processes.

• Primary succession starts on bare land with no previous life, while secondary succession starts after a disturbance where life previously existed.

• Both start on bare land with no previous life.

• Both occur only in aquatic environments.

• Primary succession occurs after a disturbance, while secondary succession starts on bare land.

Put the following in the correct order of stages in primary ecological succession as shown in the diagram?

• Grasses, herbs, shrubs, tree seedlings

• Exposed rocks

• Aspen, black spruce, jack pine

• Lichens and mosses

• White spruce, balsam fir, paper birch

Which organisms are typically the first to colonize exposed rocks during primary ecological succession?

• Lichens and mosses

• Grasses and herbs

• Aspen and jack pine

• White spruce and balsam fir

Why are lichens and mosses important in the process of primary ecological succession?

• They help break down rocks to form soil for other plants to grow.

• They provide shade for larger trees.

• They are the final stage of succession.

• They prevent erosion by covering the soil.