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Ecosystem Balance
8.L.1.1
Ecosystem Organization
1. Ecosystems are complex, interactive systems
that include both biological (biotic) and physical
(abiotic) components of the environment.
• Disruptions to any physical or biological
component of an ecosystem can lead to shifts in
all of its populations.
Ecosystem Organization
2. Groups of the same organisms (species) form
populations populations form communities
communities form an ecosystemall of the
ecosystems on Earth make up the Biosphere.
• Like individual organisms, ecosystems are
sustained by the continuous flow of energy.
Populations in Ecosystems
• A population is a group of organisms belonging to the
same species that live in a particular area.
• Population density measures the number of individual
organisms living in a defined place.
• Regulation of a population is affected by limiting factors
that include:
1. Density Dependent
2.Density Independent
3.Abiotic Factors
4.Biotic Factors
Density Dependent Factors
1. Limiting factors that operate more
strongly on large populations than
on small ones.
2. Examples include: competition (for
food, water, shelter and space),
predation, parasitism and disease.
• These limiting factors are triggered
by increases in population density
(crowding).
Density Independent Factors
1. Limiting factors that are those
that occur regardless of how large
the population is and reduce the
size of all populations in the area
in which they occur.
2. DI are mostly abiotic (such as
weather changes) and human
activities (such as pollution) and
natural disasters (such as fires).
Abiotic vs. Biotic Limiting Factors
1. Abiotic factors are nonliving
things in an ecosystem and
may be physical or chemical.
2. Examples are water,
nitrogen, oxygen, salinity, pH,
soil nutrients and
composition, temperature,
amount of sun and
precipitation
Abiotic vs. Biotic Limiting Factors
1. Biotic factors include all
of the living components
of an ecosystem.
2. Examples are bacteria,
plants, fungi or animals.
Limiting Factors and Population Change
• A change in an abiotic or a biotic factor may
decrease the size of a population if it cannot
adapt to or migrate from the change.
• A change may also increase the size of a
population if that change enhances its ability to
survive, flourish or reproduce.