Review
ecosystems
made up of all of the organisms in
an area and all of the non-living
parts of the environment
It includes the relationships of the
organisms with each other.
biotic factors
the living components of an
ecosystem
abiotic factors
the non-living components of an
ecosystem
Many are recycled and reused in
ecosystems.
organism
a
living thing
limiting factor
anything that restricts the number of
individuals that can live in an
ecosystem
resource
any product of the environment that
is used by humans or other
organisms
carrying capacity
the largest number of individuals of
the same species that an area can
support
Interactions of Life
How are living things
organized?
A living thing is called an
organism.
Example: a deer
species

A group of similar animals that can breed to
produce fertile offspring

Example: raccoons
Procyon lotor

All of the organisms of the
same species that live in an area
at the same time is called a
population.
Example: a
herd of deer
All the populations of all species
that live in an area is called a
community.
Example: deer + rabbits + bears
All the organisms living in an area,
as well as the non-living parts of
their environment, is called an
ecosystem.
Example: deer + rabbits + bears +
sunlight + soil + air water +
carbon + nitrogen
Large geographic areas that have
similar climates and ecosystems are
called biomes.
Example: tundra, taiga, desert, etc.
What is the order from
smallest to largest?

Organism
 Population
Community
Ecosystem
Biome
Organism
Population
Community
Ecosystem
Biome
What affects populations
within an ecosystem? In
other words, what
determines how many
deer, or other organisms
live in an area?
limiting factor
Anything that restricts the
number of individuals in a
population is called a limiting
factor. This would include food,
water, and living space.
When resources are plentiful, a
population generally grows.
carrying capacity
The largest number of individuals
of one species that an ecosystem
can support over time is called
carrying capacity. Carrying
capacity is determined by the
limiting factors in an area.
When a population reaches the
carrying capacity, its size
remains fairly constant.
However, when environmental
conditions change, the carrying
capacity also changes.
 Think
about what would change
for a population or ecosystem if
there was a drought.
 Change can affect the survival
of both individual organisms
and an entire species.
Human Interference
 Human
activity can also contribute
to a loss of habitat.
 Development for housing,
industry, and agriculture reduces
the habitat of native organisms.
 This can happen in a number of
different ways.
deforestation
 Development
can eliminate habitat
and native species directly. In the
Amazon rain forest of South America,
developers have cleared hundreds of
thousands of acres.
 The Amazon rain forest is cleared for
cattle ranches, logging, and urban use.
Let’s look at an example where
man has affected the population
of an organism with dire
consequences. We call this
“The Lesson of the Kaibab”