An ecosystem consists of all the living organisms in a particular area, along with the abiotic (non-living) parts of their environment. It can be large, like a forest, or small, like a puddle. Within an ecosystem, populations of different species interact as part of the community. Organisms find their niche by obtaining resources like food and shelter while competing with other populations. Diversity within an ecosystem is important, as it creates a complex web of connections between organisms. Human activities can negatively impact ecosystems by reducing diversity.

1. Unit 5 Lesson 1 What Is an Ecosystem?
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2. Unit 5 Lesson 1 What Is an Ecosystem?
What Is an Ecosystem?
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• An organism’s environment is all the living and
nonliving things that surround and affect the
organism.
• Environments include biotic and abiotic parts.
Biotic parts are living things in an environment,
such as plants, animals, and other organisms.
• Abiotic parts are nonliving things in an
environment, such as climate, water, soil, light,
air, and nutrients.

3. Unit 5 Lesson 1 What Is an Ecosystem?
What Is an Ecosystem?
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• Abiotic parts of an environment have an important
role. Temperature and amount of water affect
which plants and animals can live in a place.
• An ecosystem is all the organisms living in a
place together with their environment. Each
ecosystem has its own living and nonliving things.
• An ecosystem can be huge, such as a large forest
or desert, or it can be small, such as a mud
puddle or a single bush.

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• A group of organisms of the same species in an
ecosystem is called a population.
• Each ecosystem contains different groups of living
things. A savanna ecosystem may contain
populations of zebras as well as grasses and trees.
Unit 5 Lesson 1 What Is an Ecosystem?
Populations and Communities

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• The different populations that share an ecosystem
make up a community.
• A community consists of all the populations that
live and interact in an area.
Unit 5 Lesson 1 What Is an Ecosystem?
Populations and Communities

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• Populations in every ecosystem need food, water,
shelter, and space to live.
• The interaction between populations to meet these
needs is called competition.
Unit 5 Lesson 1 What Is an Ecosystem?
Populations and Communities

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• Populations that compete and obtain enough
resources will survive, while those that cannot
compete will not survive.
• These resources are called limiting factors,
because there is only enough food, water, shelter,
and space to support a certain number of
organisms.
• Competition also occurs within populations.
Stronger individuals get the most food and best
shelter. Thus, weaker individuals may not survive.
Unit 5 Lesson 1 What Is an Ecosystem?
Populations and Communities

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• An organism’s habitat is the place where it lives
within an ecosystem. Several populations share
the same habitat.
• An organism’s niche is its complete role or
function in its ecosystem. A niche includes all the
ways the organism survives.
• An organism’s niche includes how it finds food, as
well as the climate in which it thrives.
Unit 5 Lesson 1 What Is an Ecosystem?
Find Your Niche

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• Every organism has a niche. Having different
niches allows different organisms to survive in the
same habitat.
• Organisms with a specific way of living have a
narrow niche. For example, an animal that eats
only one type of food cannot survive without that
food.
• Organisms with narrow niches tend to live in
specific places, while those with broad niches
often move around large areas.
Unit 5 Lesson 1 What Is an Ecosystem?
Find Your Niche

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• Populations can share a habitat but not the same
niche.
• For example, red-shouldered hawks and barred owls
share a habitat, but have different niches. They both
hunt different prey at different times of the day.
• If two populations of organisms share a niche, they
must compete for resources.
Unit 5 Lesson 1 What Is an Ecosystem?
Find Your Niche

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• Diverse means different in kind. Diversity is the
variety of different species that live in an ecosystem.
• An ecosystem that is very diverse contains many
species. Ecosystems without much diversity may be
inhabited by only a few species.
• Organisms are connected in a large, complex web.
The more types of organisms in an ecosystem, the
larger the web, and the more resources available.
Unit 5 Lesson 1 What Is an Ecosystem?
Diversity

12. • Climate and location affect the amount and types
of resources that are available for organisms.
• Generally, very diverse ecosystems, such as coral
reefs and rain forests, are near the equator. Less
diverse ecosystems are farther from the equator.
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Unit 5 Lesson 1 What Is an Ecosystem?
Diversity

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Unit 5 Lesson 1 What Is an Ecosystem?
• Humans can damage ecosystems and affect
diversity by reducing the number of species living
in the ecosystem.
• Activities such as overhunting or destroying
forests to build may lower the numbers of
important species.
• Species in those environments have lost their
habitats, and diversity has decreased.
Diversity