Download File - Environmental Science

Succession
Objective: I will analyze the
relationship between ecological
succession and species movements.
ECOLOGICAL SUCCESSION:
COMMUNITIES IN TRANSITION
• New environmental conditions allow one group
of species in a community to replace other
groups.
• Ecological succession: the gradual change in
species composition of a given area
• Primary succession: the gradual
establishment of biotic communities in lifeless
areas where there is no soil or sediment.
• Secondary succession: series of
communities develop in places containing soil
or sediment.
Primary Succession
• Primary succession- occurs on surfaces that are
initially devoid of soil.
Lichens
Exposed
and mosses
rocks
Fig. 7-11, p. 156
Secondary Succession
• Secondary succession- occurs in areas that
have been disturbed but have not lost their
soil.
Fig. 7-12, p. 157
Aquatic Succession
Primary Succession:
Starting from Scratch
• Primary
succession
begins with an
essentially
lifeless are
where there is
no soil in a
terrestrial
ecosystem
Figure 7-11
Secondary Succession:
Starting Over with Some Help
• Secondary
succession
begins in an
area where
the natural
community
has been
disturbed.
Figure 7-12
Can We Predict the Path of
Succession, and is Nature in
Balance?
• The course of succession cannot be precisely
predicted.
• Previously thought that a stable climax
community will always be achieved.
• Succession involves species competing for
enough light, nutrients and space which will
influence it’s trajectory.
ECOLOGICAL STABILITY AND
SUSTAINABILITY
• Living systems maintain some degree of stability
through constant change in response to
environmental conditions through:
•
•
•
Inertia (persistence): the ability of a living system
to resist being disturbed or altered.
Constancy: the ability of a living system to keep
its numbers within the limits imposed by
available resources.
Resilience: the ability of a living system to
bounce back and repair damage after (a not too
drastic) disturbance.
Metapopulations
• Metapopulations- a group of spatially distinct
populations that are connected by
occasional movements of individuals
between them.
Survivorship Curves:
Short to Long Lives
• The way to represent the age structure of a
population is with a survivorship curve.
• Late loss population live to an old age.
• Constant loss population die at all ages.
• Most members of early loss population,
die at young ages.
Survivorship Curves
Distribution Patterns
• Most populations live in clumps although other
patterns occur based on resource distribution.
Figure 8-2
Distribution Patterns:
Clumped
• Clumped: most common type of distribution
• Usually in environments with patchy
resources so animals clump around the
crucial resources
• Mechanism to protect from predation
• Mechanism for offspring who need parental
care
• Ex: Lions, giraffes, elephants, gazelle…
Distribution Patterns:
Uniform
• Uniform: evenly spaced distributions
• Found in populations where individuals need
to maximize space between each other
• Usually arises from competition over
resources or territory
• Ex: penguins, creosote plant, agriculture
•
Fun Fact: The creosote plant releases chemicals that inhibit the
growth of other plants around it which results in uniform
distribution
Distribution Patterns:
Random
• Random: least common form of distribution
• Occurs in habitats where environmental
conditions and resources are consistent
• Lack of social interactions among species
• Ex: dandelions, fig trees, oysters…