Today’s Topic Evolution: Succession Learning Goal:
SWBAT differentiate between primary and secondary succession, and predict how a community will return to a state of equilibrium.
Have a seat and take out your notebooks.
I will pass out a study guide momentarily.
Homework
Complete the Simulating Adaptations Lab (Three Days Late)
Complete cattle, cows, and dogs articles. (Five Days Late)
Upcoming Test
Our next test will take place on Friday, 4/17.
It will cover all of Evolution: Biological Evolution Natural Selection Artificial Selection Adaptations Extinction Succession
After the Disasters What percentage of life constitutes a “mass-extinction event”?
What happened during the Cretaceous-Paleogene extinction event?
How does the world even begin to recover after such a horrible catastrophe?
After the Disasters The answer lies within Ecological Succession. Ecological succession refers to the somewhat predictable series of changes over time that a community will experience after a disturbance.
CrashCourse Video To help introduce this idea, we are going to watch a ten-minute episode of CrashCourse.
Please pay attention to the following:
1. What historical error does the presenter make? 2. The following terms: Disturbance, Ecological Succession, Primary Succession, Pioneer Species, Secondary Succession, Climax Community
What is a Disturbance? To set off the entire process of succession, a destructive event needs to a occur – or a disturbance.
A disturbance is any change in a community’s environment, large or small.
Examples of Disturbances A community may experience natural or human-caused disturbances such as: Climate Change Storms Floods Fire
Succession Prior to a disturbance, a community may be in a state of equilibrium (stable and balanced.)
Characteristics such as limiting factors hold the community at its carrying capacity.
However, a disturbance will throw the community into disequilibrium, forcing the community to adjust.
Types of Succession There are two types of succession, one more severe than the other:
Primary Succession
Secondary Succession
Primary Succession When a disturbance is so severe that no vegetation or soil life remains, primary succession occurs.
In primary succession, a community restarts itself from scratch.
It occurs after a large expanse of rock, sand, or sediment is exposed for the first time.
Primary Succession Some causes for primary succession to occur are: Glacial Retreat
Primary Succession Some causes for primary succession to occur are: Lakes Drying Up
Primary Succession Some causes for primary succession to occur are: Volcanic Lava or Ash Spreading
How to Primary Succession: Step 1: Pioneer Species
To start the rebuilding process, you will need a pioneer species.
A pioneer species is a species that is the first to colonize newly exposed land.
They are normally very well adapted for colonization.
How to Primary Succession: Step 1: Pioneer Species
Pioneer species tend to have spores or seeds that can travel long distances.
Examples:
Lyme Grass
How to Primary Succession: Step 1: Pioneer Species
Examples:
Green Algae
How to Primary Succession: Step 1: Pioneer Species
Examples:
Lichen
Primary Succession: Step 2 Get Tiny Plants
Lichens, for example, excel at breaking down the surface of rocks – which creates soil.
From this soil, small plants will begin to form.
Primary Succession: Step 3 Get Tiny Insects
As the small plants begin to grow, small insects and worms will begin to move in.
Primary Succession: Step 4
Thrive! As new organisms arrive, they will continue to change the environment by providing more nutrients and habitat for future arrivals.
Primary Succession: Step 4
Thrive! As time passes, larger plants establish themselves, the amount of vegetation increases, and species diversity increases.
Secondary Succession In secondary succession , a disturbance dramatically alters an existing community, but it does not destroy all living things or organic matter in the soil.
Some of the soil from the previous ecosystem remains.
As a result, secondary succession occurs faster than primary succession.
Secondary Succession Some causes for secondary succession to occur are: Fires
Secondary Succession Some causes for secondary succession to occur are: Logging
Secondary Succession Some causes for secondary succession to occur are: Farming
Secondary Succession Because preexisting soil exists in the community, secondary succession is much faster.
In The End… Once a community transitions back to a state of equilibrium, the succession will lead to a climax community.
A climax community is a stable community that “completes” the succession process.
Climax Community The organisms that will thrive in a climax community are determined by the climate, soil, and other factors.
Climax Community However, just because a community arrives to its climax state does not guarantee that it will always get there again if a disturbance occurs.