Name ______________________________________ Date _________
TEKS Review
3.9A
TEKS 3.9A observe and describe the physical characteristics of environments and how they support
populations and communities within an ecosystem
Environments and Ecosystems
Neighbors in Nature
What is around you right now? Look
around. Are there desks and chairs? Are there
walls and other students? Many of the things
around you affect you every day. The same
goes for all living things. Every living thing
has an environment. An environment is made
of all the living and nonliving things that
surround and affect a living thing. An
environment includes things you can touch as
well as the conditions of an area, such as the
weather.
Two organisms can live near each other
and have very different environments. For
example, a deer’s environment may include
the forests and fields for several kilometers in
any direction. The environment of an
earthworm living in the soil just a few inches
below the deer is very different. The deer and
the earthworm may never see one another.
They live in the same area, but their
environments are very different.
If you look at the connections among
living things, you can outline areas that have a
lot of connections. Very few connections go
outside the area. These areas are called
ecosystems. An ecosystem includes all the
living things in a certain area as well as the
nonliving aspects of the environment.
Ecosystems can be large or small. You
could study the ecosystem in one small pond
or the ecosystem of a large national forest.
Some ecosystems may be temporary, such as
watering holes during a rainy season. Others
have remained mostly unchanged for
thousands of years.
In a grassland ecosystem, all these
living things interact with one
another and with the nonliving
elements of their environment.
You might think that earthworms and
deer are not affected by one another. In
reality, almost all organisms in an area are
connected in some way. For example,
earthworm tunnels and droppings make the
soil more fertile. When there
are more earthworms, more
plants are able to grow,
which provide food for
more deer.
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TEKS 3.9A
Page 1 of 6
Name ______________________________________ Date _________
TEKS Review
3.9A
Populations and Communities
A Closer Look: Forest Environments
A scientist who studies interactions in
ecosystems is an ecologist. Some ecologists
study populations within an ecosystem. A
population consists of all the individuals of
one species in an ecosystem. You can count or
estimate the number of individuals to find the
population size. Many ecologists track how
changes in an ecosystem affect the population
size of different species.
The characteristics of a forest
environment make it possible for many things
to live there. The soil is deep and full of
nutrients, and there is enough rainfall for trees
to grow close together. The trees and other
plants provide food and shelter for many
animals. Woodpeckers find insects that live
under tree bark. Owls nest in holes in trees.
Salamanders, worms, and many insects live
under the decaying layer of leaves on the
forest floor.
Other ecologists specialize in studying
communities. A community is composed of
all the populations living and interacting in an
ecosystem. For example, an ecologist may
find that the community has fewer members—
or fewer species—in ecosystems that have
been altered by people.
Characteristics of Environments
A forest environment is very different
than a pond environment. In fact, each
environment on Earth has unique
characteristics. These characteristics make
different environments good homes for some
plants and animals but not for others.
Many of the characteristics that affect
living things in an ecosystem are nonliving, or
abiotic, factors. These are part of the physical
environment in an ecosystem. The sun, air,
water, soil, and climate are all abiotic factors.
Each population interacts with the
physical environment. Plants need the sunlight
to grow, and they take water and nutrients
from the soil. Fish and frogs live in water that
birds and other animals drink.
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A Closer Look: Desert Environments
When you observe a desert environment,
you do not see many living things. That’s
because there is not much precipitation in a
desert. The things that live there must have
body parts or behaviors to help them survive.
Cacti store water in their thick stems. Many
animals burrow underground or stay in the
shade when it is hot. Flowering plants grow
very fast after it rains so they can make seeds
before the sandy soil dries out again.
A Closer Look: Pond Environments
Finding water in a pond environment is
no problem most of the time. Water lilies,
reeds, fish, frogs, turtles, and other aquatic
organisms live in the water. Many insects live
in or near the water, and they provide food for
fish and birds. Some ducks eat
vegetation that grows in the pond.
Other ducks dive underwater and
catch fish.
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Name ______________________________________ Date _________
TEKS Review
3.9A
Materials
Hands-On Activity
Observe a Pond Ecosystem
The physical characteristics of many ecosystems are constantly changing.
Sometimes, these changes happen quickly. Other times, the changes take
hundreds of years. In this activity, you will make a model of a pond
ecosystem, and you will see how the ecosystem changes as the pond dries up.
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ruler
potting soil
plastic dishpan
water
duckweed
birdseed
notebook
camera (optional)
watering can
Procedure:
1. Make a model of a pond by spreading 5 cm of moist potting soil in the dishpan. Dig out a
low spot in the center, leaving 1 cm of soil. Pile up soil around the low spot to make
gently sloping sides.
2. Slowly pour water into the low spot until the water is 4 cm deep. Put duckweed in the
“pond.”
3. Sprinkle birdseed over the soil. Do not water it. Make a drawing in your notebook or take
a photograph to record how your pond looked.
4. Every other day, use a watering can to add a small amount of water to the pan. Add water
as if it were raining on the entire area, until the pond is ½ cm below the level it was the
last time you added water. This will simulate a pond that is drying up.
5. Each time you add water, record your observations in a notebook. In addition to tracking
the appearance of the living things, record changes in the physical environment.
6. When the pond has dried up, wait two days and make a final set of observations.
Discussion Questions:
1. What changes did you observe?
2. What can you infer caused the changes?
3. How can the physical environment help living things survive?
4. How can the physical environment harm living things?
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TEKS 3.9A
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Name ______________________________________ Date _________
TEKS Review
3.9A
Environments and Ecosystems
Look at the environment shown below. List 4 animal populations you would expect to find.
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Describe the physical characteristics of a desert environment.
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Choose an ecosystem to research. Draw the ecosystem and include as many
parts as you can fit. Label all the parts that you include.
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TEKS 3.9A
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Name ______________________________________ Date _________
TEKS Review
3.9A
TEKS Assessment 3.9A
Fill in the letter of the best choice.
Which animal is able to meet its needs in
a pond environment?
Look at the forest environment below.
Which statement BEST describes the
interactions that occur?
The squirrels do not interact with
the other living things.
The mushrooms and other
decomposers are abiotic parts
of the environment.
The population size of all living
things in the environment remains
constant over time.
All living things in the environment
are connected in some way.
You see a raccoon in a city park. What
can you conclude?
It is lost.
It is happy.
It is someone’s pet.
What forms a biological community?
It has found food and shelter.
a city and its resources
several populations
Which is the abiotic factor that limits the
number of organisms in a desert?
an ecosystem
an environment
air
water
light
predators
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TEKS 3.9A
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Name ______________________________________ Date _________
TEKS Review
3.9A
Answer Key
Hands-On Activity (p. 3)
1. Answers will vary. Students should note that the duckweed grew well when there was
plenty of water. As the pond dried up, the duckweed population decreased. The plants
growing from seed grew well in the drier soil, but they were not able to grow in the deeper
water of the pond.
2. The decrease in the amount of available water may have caused the changes.
3. The physical environment provides many of the basic needs for living things, including
air and water. It also provides light to plants.
4. When the physical environment changes and it can no longer provide for the basic needs
of certain living things, those things must find a new place to live or they may not survive.
Student Response Activity (p. 4)
1. Answers will vary. Sample answer: deer, squirrels, raccoons, and earthworms
2. A desert environment has very sandy soil. It receives only small amounts of precipitation
each year. Because there are no tall trees to block it, the sun may be intense.
3. Check students’ drawings and labels for accuracy.
TEKS Assessment (p. 5)
1. A
2. D
3. B
4. D
5. B
TEKS Review and Assessment
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TEKS 3.9A
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