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.