Transcript Sept27MonSuccession

SUCCESSION
Natural Change Over Time
Organization in Ecology
Ecosystem
Community
Population
Organism
Ecology also studies how
ecosystems change over time
and how communities recover
from a disturbance.
This is called SUCCESSION.
What Is Succession?
The orderly, natural
progression of stages that
communities of an ecosystem
go through
Two kinds of SUCCESSION.
 There are two kinds of succession, depending on
how the ecosystem starts out or how an ecosystem
is disturbed
PRIMARY
SUCCESSION
 The colonization of barren land by communities
of organisms
 Primary Succession happens when a
disturbance destroys the entire community so
that there is not even any soil left behind
 For example a glacier could melt away to
expose bare rock.
PRIMARY
SUCCESSION
 Another way to think of primary succession is that it
occurs when life enters an area for the first time.
 In this case the land is completely devoid of soil and
vegetation
SECONDARY SECESSION
 Sequence of changes that takes place after
an existing community is severely
disrupted in some way
 However, the disturbance was not big
enough to remove the soil.
 Secondary succession might occur after
land is cleared for farming, or after a forest
fire.
SECONDARY SECESSION
 In secondary succession, the dominant plants in the
community are removed, allowing new plants to
colonize.
PIONEER SPECIES
 The first species that move into a barren or
disturbed area
 Pioneer Species are tough and can live in conditions
that other organisms cannot
 Many PIONEER SPECIES create soil. For example,
lichen attaches to rocks and breaks them down into
soil. Mosses and grasses can also be pioneer
species.
 Pioneer Species often colonize a new area by seeds
being blown by the wind.
PIONEER SPECIES
 Please answer the following questions on your own:
Why are mosses and lichens pioneer species, but pine
trees and deer are not?
CLIMAX COMMUNITY
 A stable, mature community that undergoes little or
no change in species
 A CLIMAX COMMUNITY is what the community
would be like if no disturbances ever occurred.
 Some ecosystems contain a climax community for
hundreds or thousands of years. In other
ecosystems, as soon as a climax community is
reached a disturbance becomes much more likely.
 For example, some climax communities use up the
nutrients in the soil or increase the likelihood of a fire
CLIMAX COMMUNITY
 Another way to think of a climax community is an
ecosystem that has a steady amount of TOTAL
BIOMASS.
Pioneer species – the first
species to populate an area. These
#1.6 Aim:
species
start making the soil
How do ecosystems change over
time?
Agenda
QOD (10)
Climax community – a mature,
stable community - what the
community would be like if no
disturbances ever occurred.
 Lichens and mosses are an important
pioneer species 
Lesson: succession (15)
Typical forest succession
 Lichens and mosses
 Flowers and weeds
 Non-woody plants and
grasses
 Woody shrubs, grasses,
tree saplings
 Young forest
 Mature trees
As the ecosystem changes, the animals change to accommodate the available
food and shelter.
Forests
What does this graph tell us
about succession?
Primary or Secondary?
Volcanic Eruption
Clear Cutting
Primary or Secondary?
Tornados
Mudslide
Exit Ticket
 1) What is the difference between PRIMARY and SECONDARY
succession?
 2) How do PIONEER SPECIES help speed up the process of
ecological succession?