Warm-up: Succession

• Read the Case Study,

“Communities Maintained by Fire”

on pages 130 – 131.

• Write two things you have learned and

• answer questions #1 & 2.

Warm-up Answers

• 1. New things you have learned…• The purple plant Fireweed covers the burned

forest areas of the Rocky Mountains. • Ecological Communities (Biomes) that are

maintained by fire are:

Chaparral of California, Temperate Grasslands of the Midwest, many Southern and Western Coniferous forests.

• Seeds of some species will not germinate until exposed to temperatures of several hundred degrees.

Changes in Ecosystems:Ecological Succession

What is Ecological Succession?

•Natural, gradual changes in the types of species that live in an area

•Can be primary or secondary •The gradual replacement of

one plant community by another through natural processes over time

Primary Succession

• Primary succession occurs where there was no previous community, such as on bare rock or sand.

• Begins in a place without any soil:

»Sides of volcanoes»Landslides»Flooding»Glacial retreat

• Primary succession begins with PIONEER SPECIES.

Pioneer organisms can tolerate extreme conditions: hot and cold; dry and wet.

Moss, dune grass, and lichens are pioneer organisms.

• First, lichens that do not need soil to survive grow on rocks

• Next, mosses grow to hold newly made soil

Pioneer Species

Lichens break down rock to form soil.

Low, growing moss plants trap

moisture and prevent soil

erosion

Lichens

Lichens are algae and fungus growing together in a mutualistic relationship. •Algae make the food•Fungus anchor and capture water.

Primary Succession

• Soil starts to form as lichens and the forces of weather and erosion help break down rocks into smaller pieces

• When lichens die, they decompose, adding small amounts of organic matter to the rock to make soil

Primary Succession with lichens and mosses.

Primary Succession

• Simple plants like mosses and ferns can grow in the new soil

Primary Succession

• The simple plants die, adding more organic material (nutrients to the soil)

• The soil layer thickens, and grasses, wildflowers, and other plants begin to take over

Primary Succession

• These plants die, and they add more nutrients to the soil.

• Shrubs and trees can survive now.

Primary Succession• Insects, small birds, and mammals

have begun to move into the area.• What was once bare rock, now

supports a variety of life.

Secondary Succession

•Begins in a place that already has soil and was once the home of living organisms

•Occurs faster and has different pioneer species than primary succession

Secondary Succession

•Newer communities make it harder for the older communities to survive.

–Example: Younger birch trees will have a harder time competing with taller, older birch trees for sun, but a shade loving tree may replace the smaller birch trees.

When does secondary succession occur?

• After forest fires• After cultivated land is abandoned• Temporary flooding from storms,

etc.

Climax Community

•A relatively stable group of plants and animals that is the end result of the succession process– However, stability never happens for long

in ecology! The only constant is CHANGE!

•Does not always mean big trees–Grasses in prairies–Cacti in deserts

• The following slide is an example of the Secondary Succession of a deep freshwater pond.

https://www.youtube.com/watch?v=k03vxRYsJ4Y