Interactions of
Living Things
The Environment
Ecology
All organism, from the smallest bacteria
to a blue whale, interact with their
environment
 Ecology: the study of the interactions
among organisms and their environment
 Abiotic factors: nonliving parts of the
environment
 Biotic factors: living or once-living
organisms in the environment

Abiotic Factors
Examples of abiotic factors: water,
sunlight, temperature, air, and soil
 These factors are important in
determining which organisms are able
to live in a particular environment

Ecologist study biotic
and abiotic factors in
an environment and
the relationship
among them. Many
times, ecologists must
travel to specific
environments to
examine the
organisms that live
there.
Water
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All living things need water to survive
The bodies of most organisms are 50 – 95%
water
More than 95% of Earth’s surface water is
found in the oceans
Saltwater environment in the oceans is
home to a vast number of species
Freshwater environments support
thousands of types of organisms
100%
80%
60%
saltwater
40%
freshwater
20%
0%
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Saltwater accounts for 97% of the water on
Earth. It is found in the seas and oceans.
Only 3% of Earth’s water in freshwater
Light
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Light and temperature affect the environment
The availability of sunlight is a major factor in
determining where green plants live
Algae live near the water’s surface where
sunlight can penetrate
Little sunlight reaches the forest floor, so very
few plants grow close to the forest floor
Flowers that grow on the forest floor grow during the spring when they
receive the most sunlight.
Temperature
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Temperature can determine which plants
and animals can live in a region
Some areas of the world have a fairly
consistent temp. year round, but others vary
Water environments throughout the world
also have a widely varied temp.
Plant and animal species found in the
freezing cold Arctic, in the extremely hot
water, and every temp. in betwee,
Air
Although you can’t see the air that
surrounds you, it has an impact on the
lives of most species
 Composed of a mixture of gases
 Polluted air can cause the species in
an area to change, move, or die off
 All species are affected by the weather
in the area that they live

Air pollution can come from many different sources. Air quality in an
area affects the health and survival of the species that live there.
Soil
From one environment to another, soil
can vary greatly
 Soil type is determined by the amounts
of sand, silt, and clay it contains
 Different plants need different kinds of
soil
 Soil affects every organism in an
environment

Soil provides a home for many species of animal.
Biotic Factors
Abiotic factors do not provide everything
an organism needs for survival
 Organisms depend on other organisms
for food, shelter, protection, and
reproduction
 How organisms interact with one
another and with abiotic factors can be
described in an organized way
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Levels of Organization
The living world is highly organized
 Atoms – molecules – cells – tissues –
organs – organ systems – organisms
 Biotic and abiotic factors also can be
arranged into levels of biological
organization

– Organism – population – community –
ecosystem – biome – biosphere
Organism: An organism is one individual from a population.
Populations
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All the members of one species that live
together make up a population
EX. All of the catfish living in a lake at the same
time make up a population
Members of a population compete for food,
water, mates, and space
The resources of the environment and the ways
the organisms use these resources determine
how large a population can become
Population: All of the individuals of one species that live in the same
area at the same time make up a population
Communities
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Most populations of organisms do not live
alone
They live and interact with populations of other
types of organisms
Groups of populations that interact with each
other in a given area form a community
Populations of organisms in a community
depend on each other for food, shelter, and
other needs
Community: The populations of different species that interact in some
way are called a community.
Ecosystem
Ecosystem is made up of a biotic
community and the abiotic factors that
affect it
 Ex. Coral reefs, forests, and ponds
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Ecosystem: All of the communities in an area and the abiotic factors that
affect them make up an ecosystem.
Biomes
Scientist divide Earth into different
regions called biomes
 A biome is a large region with plant
and animal groups that are well
adapted to the soil and climate of the
region
 Many different ecosystems are found
in a biome
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Biome: a biome is a large region with plants and animals well adapted to
the soil and climate of the region.
This map shows some of the major biomes of the world. What biome do
you live in?
Biosphere
The part of Earth that supports life is
the biosphere
 Includes the top part of Earth’s crust,
all the waters that cover Earth’s
surface, the surrounding atmosphere,
and all biomes
 The biosphere is only a small part of
Earth
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Biosphere: The level of biological organization that is made up of all the
ecosystems on Earth is the biosphere.
Quiz
What is an ecosystem?
 How are the terms ecology and
environment related?
 Explain how biotic factors change in an
ecosystem that has flooded.
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Answers
All of the communities in an area and
the abiotic factors that affect them
 Ecology is the study of the interactions
among organisms and their
environment
 Organisms that do no live in water
would die. Other water organisms
might move into the ecosystem
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