Changes in Ecosystems:
Ecological Succession
1.5
Changes by Fire
• Naturally occurring catastrophic events can
change the planet we live on. Earth is
constantly changing.
• Sometimes these changes take millions of
years, but sometimes they happen in just
minutes…
MOST DEADLY AND DESTRUCTIVE VOLCANO IN THE
UNITED STATES:
MOUNT ST. HELENS
Definition of Succession
• Natural, gradual changes in the types of
species that live in an area
• The gradual replacement of one
plant/animal community by another
through natural processes over time
• Can be primary or secondary
Primary Succession
• Begins in a place without any soil
– Sides of volcanoes
– Land uncovered by retreating glacier
– After flooding when soil was washed away
• Starts with the arrival of living things such
as lichens that do not need soil to survive
• Called PIONEER SPECIES
Lichen: A combination
of algae and fungus
that can survive on
bare rock, tree bark,
and other surfaces.
Lichen is a
“pioneer species”
Other early species
include mosses and
ferns. They begin the
breakdown of rocks
into soil
These rocks are
slowly becoming the
soil!
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 tiny amounts of soil
Primary Succession
• Simple plants like mosses and ferns can
grow in the new soil
Primary Succession
• The simple plants die, adding more
organic material
• 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 in
• What was once bare rock now supports a
variety of life
I’m
cute!
Primary
Succession: Starts
on Bare Rock!
No SOIL yet.
Secondary Succession
• Begins in a place that already has soil &
was once the home of living organisms
• Occurs faster than primary succession
• Examples
– after forest fires
– after agriculture/cultivation
Secondary
Succession:
Soil already in place
Climax Community
• A stable group of plants and animals that
is the end result of the succession process
– AFTER SUCCESSION THE POPULATION
AND NUMBER OF SPECIES INCREASES!!
• Nature is all about a balance (equilibrium).
Today’s Reading/Questions
• 1. What is ecological succession?
• A. The gradual change of an
ecosystem over time; the gradual
change of the types of species that
live in an area
Today’s Reading/Questions
• 2. Explain the difference between
primary and secondary succession.
• A. Primary succession begins on bare
rock/rocky surface with no existing
soil, plants, etc. (“new” land)
Secondary succession begins with
soil already in place (nature takes
over)
Ecological Succession
Create a Venn Diagram comparing
primary and secondary succession
and underneath write a Notes
Summary!
Summary of the notes and information learned