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Food Chains and Food
Webs
Ms. McCray
6th Grade Science
April 24 & 25
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Standards We Will Address
 6.L.2.1
Summarize how energy derived from the
sun is used by plants to produce sugars
(photosynthesis) and is transferred within a food
chain or food web (terrestrial and aquatic) from
producers to consumers to decomposers.
 6.L.2.2
Explain how plants respond to external
stimuli (including dormancy and forms of tropism)
to enhance survival in an environment.
 6.L.2.3
Summarize how the abiotic factors (such as
temperature, water, sunlight, and soil quality) of
biomes (freshwater, marine, forest, grasslands,
desert, Tundra) affect the ability of organisms to
grow, survive and/or create their own food through
photosynthesis.
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Transfer of Energy
 Energy
is derived (taken) from the sun and used
by plants to produce sugars (photosynthesis) and
is transferred within a food chain or food web from
producers to consumers to decomposers.
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Difference Between Food Chains
and Food Webs
 Food
webs: show how plants and animals are
interconnected by different paths.
 Example: Trees produce acorns which provide
food for mice and insects.
Food chains: follows a single path as animals eat
each other (or eat plants)
 Example: Cow eats grass
 Example: Shark eats seal
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Types of Food Webs/Chains
There
are two places we find food
webs/chains: on land and in water.
On
In
land they are called terrestrial
water they are called aquatic
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What Are Producers?
A
producer is something that
PRODUCES it’s own food!
Plants
food is glucose which is a type
of sugar.
They
make this sugar using sun light,
water, and carbon dioxide.
This
process is called photosynthesis.
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What Are Consumers?
 Consumers
must eat other things
(plants or animals) to survive.
 There
are three types of consumers:
 Herbivores: animals
that eat only
plants
 Example: cows, rabbits
 Carnivores: animals that eat only meat
 Example: T-rex,
 Omnivores: animals that eat both
plants and animals
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What Are Decomposers?
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Bacteria
and fungi are two types of
decomposers.
Decomposers
return nutrients to the
soil and air. They extract carbon from
their food and it mixes with oxygen to
create carbon dioxide.
Examples
are rotting logs, animals
decaying, and mold on bread.
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Bacteria in the Gut
Gut
flora or bacteria live in the
digestive tract of most animals.
These
bacteria provide many useful
functions for the host (the animal they
live in) such as:
 Preventing
growth of harmful bacteria
 Producing vitamins for the host
 Producing hormones that direct the
host to store fat.
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Bacteria in Plant Roots
Bacteria
live on plant roots and they
convert nitrogen in the air into
organic compounds (a chemical that
contains carbon) that the plant can
use.
The
plant then uses these organic
compounds to make proteins that the
animals will eat and use for energy.
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Fun (and Important) Facts!
In
case you haven’t noticed, carbon is
very important to plants and animals.
Without carbon, life would not exist.
Bacteria
make up about 60% of the
dry mass of feces (poop)!!
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Levels of Organization

Species- a group of organisms that are physically similar and
can mate with each other and produce offspring that can also
mate and reproduce

Population- all member of one species in a particular area
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Community- all different populations that live together in
an area
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Predation
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An interaction in which on organism kills another for food
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Predator- the organism that does the killing
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Prey- the organism that is killed
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Standard 6.L.2.2 Changes in
Environmental Conditions
Changes
in environmental conditions
can affect the survival of individual
organisms and entire species.
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Dormancy
Dormancy
is a period of inactivity in a
mature seed prior to germination;
seed remains dormant until
conditions are favorable for growth
and development of the new plant
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Plants Adapt
Plants
grow, reproduce, and shift the
position of their roots, stems and
leaves in response to environmental
conditions such as gravity, sunlight,
temperature and day length.
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Tropism
Tropism
is a plant’s turning or
bending movement of an organism
toward or away from an external
stimulus such as light, heat or gravity.
If
the tropism is positive, the plant
grows toward the stimulus.

If the tropism is negative, the plant
grows away from the stimulus
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Biotic and Abiotic Factors
 Water, nitrogen, carbon
dioxide, and
oxygen are substances cycled between
the living and non-living environments.
 Abiotic
factors are any non-living things
in an environment.
 Examples: air, water, sunlight
 Biotic
factors are any living things in an
environment.
 Examples: plants
and animals
 Soil (organic matter) has both biotic and
abiotic components.
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Standard 6.L.2.3 Abiotic/Biotic
Factors
Refresher:
What is the difference
between abiotic and biotic factors?
What
are examples of each?
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Different Environments
Biomes:
the world's major
communities, classified according to
the predominant vegetation and
characterized by adaptations of
organisms to that particular
environment.
Biomes
we will focus on:
 Freshwater, marine, forest, grassland,
tundra, desert
 Others include: tropical rainforest,
mountain, savannah and tundra
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Aquatic Biomes:
Freshwater & Marine

Freshwater: Includes
streams, rivers, ponds
and lakes
Marine: covers about ¾ of
the Earth’s surface and
includes oceans, coral
reefs and estuaries
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Forest Biome:
Large
assortments of trees, plants
and animals which vary
depending on the zone’s climate
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Grassland Biome
An
area that is populated
mostly by grasses and other
non-woody plants
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Desert Biome
An
area that received less
than 25 centimeters of rain
a year
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Tundra Biome
Extremely
cold and dry
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Limiting Factors For Any Biome
Environmental
factors that affect an
organism’s ability to survive in its
environment, such as food availability,
predators, and temperature, are
limiting factors.
A
limiting factor is any biotic or
abiotic factor that restricts the
existence, number, reproduction, or
distribution of organisms.
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Limiting Factors Continued
Can
you think of a limiting factor that
would affect the organisms around
Overhills?
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One Example of Limiting Factors
At
high elevations, the wind is too
strong, temperatures too cold, and soil
to thin to support the growth of large
trees. All that grows in this
environment is grasses, mosses, and
ferns.
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Limiting Factors Can Impact
Multiple Species
Example:
water is limited in a
grassland area, reducing the number
of seeds produced. The rabbits
depend on the grass for food. If there
are fewer seeds, there’s less grass.
Less grass= fewer rabbits. Hawks,
which feed on rabbits, have less food
in return.