Abiotic Factors

Chapter 13: Principles of Ecology
Section 13.2
Biotic and Abiotic Factors
• To be able to identify biotic and abiotic
elements in an ecosystem.
• To be able to describe how a change in one
element in an ecosystem can affect others.
• To be able to compare and contrast how
ecosystems have been altered due to changes
in biotic and abiotic changes.
• I would like you to imagine yourself first in a
woodland then in a desert.
• Now, I want you to pick up a handful of soil in
each place. What differences would you find?
• Woodland soil is rich in organic matter and
holds water well. The desert’s sandy soil has
little organic matter and does not hold water.
Ecosystem – Biotic and Abiotic
• Ecosystems are made up of living and nonliving components.
These components are
referred to as biotic
and abiotic factors.
While they are
considered separate,
they act upon one
another in often
complex ways.
Ecosystem – Biotic and Abiotic
Biotic Factors
• Biotic factors are living things, such as plants,
animals, fungi, and bacteria.
– Each organism plays a particular role in the
– Ex. fungi breakdown organic material, earthworms
enriching the soil, methane consuming Achaea,
turkey vultures consuming carrion, wolves hunting
moose, etc.
Biotic Factors
on Isle
in Lake
A methane consuming deep
sea Achaea
Turkey Vulture
Abiotic Factors
• Abiotic Factors – nonliving things such as
water, temperature, pH, wind, sunlight,
minerals, and soil.
– The balance of these factors determines which
living things can survive in a given environment.
– Changes in only one abiotic factor can reverberate
throughout an ecosystem – causing species to
disappear or go extinct and other species to
Abiotic Factors
• Example: Coral Bleaching.
Triggered by changes in temperature, pH,
salinity, and light. Corals are very
sensitive to climate change and we are
seeing huge die offs and extinctions.
Coral reefs are the tropical rainforests of
the seas - they are second only to
rainforests in terms of biodiversity.
Major source of protein for humans all
around the world.
Abiotic Factors
• Acidification of the oceans due to greater
concentrations of carbon dioxide.
Carbon dioxide reacts with
water to form carbonic acid.
Acidification of the oceans is
a major problem because
animals depend on pH being
constant, otherwise they
cannot survive.
What are the abiotic and the biotic factors that you see in
this photo of a beaver dam? How do they interact?
What are the abiotic and the biotic factors that you see in this photo
of a beaver dam? How do they interact? (same question as last slide)
Keystone Species
• A keystone species is a species that has a
disproportionately large effect on
its environment relative to its
abundance. Such species are described as
playing a critical role in maintaining the
structure of an ecological community,
affecting many other organisms in
an ecosystem and helping to determine the
types and numbers of various other species in
the community.
• Biodiversity is the assortment, or variety, of
living things in an ecosystem.
– For example: a rain forest, like the Amazon
rainforest) has a large assortment of different
species living in proximity to one another. A
desert, on the hand is poor in biodiversity (there
are a lot fewer species living in a desert
– Two factors that influence biodiversity are rainfall
and temperature. More rainfall, like in the rain
forest, are linked with greater biodiversity.
Video – Wolves of Yellowstone
• This video ties all of the concept we have been
studying together.
– Research – field work and application of science.
– Biotic and abiotic factors
– Populations, communities, ecosystems, etc.
– Keystone species
– Biodiversity
Yellowstone Video Review
• How did the Yellowstone ecosystem change with
the reintroduction of the wolves?
– What was the condition of the park’s habitat (range)
before wolf reintroduction?
– How did the park’s habitat change after there
• What role do wolves play in the Yellowstone
– How do the wolves affect the other parks species?
• Why do we call them a keystone species?

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