N o r t h E a st I n d ep en d e nt S c h o o l D i st ric t
6th Grade Science
Unit 9
Connections in the Environment
Spring 2006
CONNECTIONS IN THE ENVIRONMENT
This 6th grade unit is a study of some basic interactions between an organism and
its environment. In the previous unit of study, students learned that organisms
are a part of a larger system that includes populations and communities. Together
with the nonliving objects in the environment, they form an ecosystem. Study of
how organisms interact with their environment, or the ecosystem at large, is called
ecology. In 6th grade, ecology studies will include identifying components of an
ecosystem, describing energy flow in food chains and webs, as well as examination
of the concepts of stimulus and response. In the later content area, the 6th grader
is to identify responses in organisms to internal stimuli such as hunger or thirst,
and identify responses in organisms to external stimuli such as the presence or
absence of heat or light.
Components and Interactions within an Ecosystem
Components of an ecosystem include biotic and abiotic factors as well as the
different the different levels these factors are organized in. The biotic
components within an environment include all organisms. Abiotic factors include all
nonliving parts of the environment, including rocks, soil, air, water etc.
A habitat is a specific place where an organism lives. Each habitat is chosen by an
organism for its abiotic factors as well as food sources which are biotic factors.
All the members of one species within a specific area is called a population.
Populations interact in various ways. Sometimes members of a population are
competitive with one another for necessary resources, and as a result, they require
their own territory. Sometimes members of a population live together and share
resources or provide protection through numbers. All the different populations of
species within an area make up a community. Various food chains and food webs
make up a community. This community of organisms along with the abiotic factors
within the area make up a specific ecosystem. An example of an ecosystem is all of
the organisms and abiotic components of the south Texas brush country. Another
example would be all of the organisms and abiotic components of the Mississippi
Clarifying statements are intended to deepen teachers’ understanding of science concepts and serve as a guide for
instructional design. They are not intended to serve as student instructional materials.
This publication is the property of North East Independent School District. Duplication in whole or in part, outside of NEISD, is
prohibited without express written permission from NEISD.
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N o r t h E a st I n d ep en d e nt S c h o o l D i st ric t
6th Grade Science
Unit 9
Connections in the Environment
Spring 2006
river delta. These ecosystems and all others in the world are collectively referred
to as the biosphere.
The ultimate source of energy for the biosphere is the sun. There are three
groups of organisms in any ecosystem that rely on the radiant energy of the sun.
They are producers, consumers and decomposers.
Producers take in energy from the sun. Grasses, shrubs, and trees are examples of
producers. They are called producers because they can make, or produce, their
own food.
Consumers get their energy from eating, or consuming, other organisms. Animals
are examples of consumers. When a consumer eats a producer or another animal
that has eaten a producer, it is getting some of that original radiant energy
provided by the sun. Herbivores are a class of animals that eat only vegetable
matter. Carnivores are a class of animals that eat only meats. Omnivores eat both.
Decomposers, such as bacteria, obtain their nutrients by breaking down wastes and
the remains of other, dead organisms.
The path or flow of energy in an ecosystem is called a food chain. A food chain
always starts with a producer. It is followed by all the animals that eat the
producer and then the other animals that eat each other in the order that the
process occurs. Below is an example of a simple food chain. It is important for
students to know that the arrows always point in the direction that the energy is
moving. In addition, they should know that not all energy is transferred. Some of
it is lost to the environment as heat.
Clarifying statements are intended to deepen teachers’ understanding of science concepts and serve as a guide for
instructional design. They are not intended to serve as student instructional materials.
This publication is the property of North East Independent School District. Duplication in whole or in part, outside of NEISD, is
prohibited without express written permission from NEISD.
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N o r t h E a st I n d ep en d e nt S c h o o l D i st ric t
6th Grade Science
Unit 9
Connections in the Environment
Spring 2006
Example of a simple food chain with arrows showing energy flow:
Many consumers do not just eat one organism. Many organisms feed off of a
variety of food. Interconnected food chains form food webs, which are more
complex. They are also more accurate at describing how many organisms interact
within the environment. Students should understand that the food web provides a
more complete picture of the flow of energy in an ecosystem. In the case of an
animal that only eats one kind of food, that animal is at risk if the food supply is
destroyed. A good example of this would be the Giant Panda. They only eat
bamboo. The bamboo forests of Asia are rapidly decreasing. If the bamboo is no
longer available, then Giant Pandas will become extinct.
Clarifying statements are intended to deepen teachers’ understanding of science concepts and serve as a guide for
instructional design. They are not intended to serve as student instructional materials.
This publication is the property of North East Independent School District. Duplication in whole or in part, outside of NEISD, is
prohibited without express written permission from NEISD.
3
N o r t h E a st I n d ep en d e nt S c h o o l D i st ric t
6th Grade Science
Unit 9
Connections in the Environment
Spring 2006
Stimulus and Response
6th grade students have not been exposed to stimulus and response before. It is
common for students to confuse the two. Students need to be able to
differentiate between the stimulus and response as well as classify the stimulus as
internal or external.
Anything that causes a response in a living organism is called a stimulus. If the
stimulus comes from within the organism, then it is internal. An example would be
hunger. If the stimulus comes from the environment, then it is an external
stimulus. An example would be jumping into a swimming pool and then feeling cold.
These survival responses help organisms find food, avoid predation, find a place to
live, hibernate when the seasons change, grow towards the light, and so forth.
Plants respond to stimuli such as gravity, light and touch. Plants grow towards
light. Some plants respond to touch. Plants known as climbers will attach to a
fence vine for support as they grow. A Venus flytrap plant will snap shut when an
insect lands on it. Each of these are examples of plants responding to an external
stimulus. Hibernation and migration are responses of animals to seasonal changes.
These would also be responses to external stimuli. The following chart provides
more examples:
Organisms
turtle
human
opossum
cactus
plant
pill bug
plant
dog
human
Stimulus
scared by noise
dry mouth
feels threatened
rain
lack of water
damp ground
light
heat
need for oxygen
Response
retreats into shell
drinks water
plays dead
blooms quickly
wilts
moves towards it
grows towards it
begins to pant
breathing
Internal or
External ?
external
internal
external
external
internal
external
external
external
internal
Clarifying statements are intended to deepen teachers’ understanding of science concepts and serve as a guide for
instructional design. They are not intended to serve as student instructional materials.
This publication is the property of North East Independent School District. Duplication in whole or in part, outside of NEISD, is
prohibited without express written permission from NEISD.
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