Ecology 3 - Food Chains Webs Energy Transfer

7/27/2019 Ecology 3 - Food Chains Webs Energy Transfer

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ECOLOGY

Food Chains,

Food Webs &

Energy Transfer



Lesson Outline• Food Chains

• Food Webs• Energy Transfer

• Carbon Cycle



Food chains

• A food chain shows the feeding

relationship among a series of organisms

through which energy is transferred in the

form of food.

• It always starts with a primary producer

and ends with a consumer .

• Each level or step in a food chain is called

a trophic level.



Food chains

1. Plants are the primary producers

• use light energy from the sun toproduce food (sugar) from carbon

dioxide and water



Food chains

2. Animals are the consumers

• Herbivores (primary consumers)

• Carnivores that eat herbivores(secondary consumers)

• Carnivores that eat other carnivores(tertiary consumers)

• Omnivores eat both plants & animals• Scavengers feed on dead animals

e.g. vultures

http://www.qrg.northwestern.edu/projects/marssim/simhtml/organisms/falcon.html

http://www.qrg.northwestern.edu/projects/marssim/simhtml/organisms/moose.html



Food chains

3. Decomposers breakdown deadorganisms

• releases mineral salts back into the

food chain for plants as nutrients• Bacteria, fungi



Food Chain –

Trophic Level• Each step/level in a food chain or food web

is known as a trophic level.

• Sequential from producer to primary

consumer to secondary consumer to

tertiary consumer.



Producer Primary

Consumer

Secondary

Consumer

Tertiary

Consumer

green plant grasshopper spider bird

Food Chain

Trophic

level 1

Trophic

level 2

Trophic

level 3

Trophic

level 4







Food webs• Most animals eat more than one kind of

food in order to meet their food and energy

requirements.

• A food web is several

food chains connected

together .





green plant

aphid

grasshopper spider bird

caterpillar

Food Web



green plant

aphid


caterpillar

Food Web





green plant

aphid ladybird


caterpillar

Food Web



Food web



Food Web-sitesFood chain BrainPOP video

• http://magma.nationalgeographic.com/ngex

plorer/0309/quickflicks/index.html

Food chain crossword puzzle

• https://reader009.{domain}/reader009/html5/04

puzzle.htm



1

Sun (light

energy)

1. In any

ecosystem, the

ultimate source of

energy is the sun.

Energy flow



1

2

Sun (light

energy)

photosynthesis

Producers (Green plants)

Energy flow

2. Light energy

absorbed bychlorophyll in

producers is

converted into

chemicalenergy during

photosynthesis.







1

2

3

3

4

4

4

5

5

Sun (light

energy)

photosynthesis

feeding

feeding

respiration

respiration

respiration

excretion

excretion

egestion

egestion

Secondary

consumers

(carnivores)

Primary consumers

(Herbivores)


Energy flow

5. Energy is also lost

through faeces, excretory

waste and dead organisms.



1

2

3

3

4

4

4

5

5

Sun (light

energy)

faeces and excretory products

+ dead bodies of organisms

decomposition

photosynthesis

feeding

(holozoic nutrition)

feeding

respiration

respiration

respiration

excretion

excretion

egestion

egestion

Secondary

consumers

(carnivores)

Primary consumers

(Herbivores)

Producers (Green plants)• Decomposers break down dead

organic matter and use some of

this trapped chemical energy for

their own needs.

Energy flow



1

2

3

3

4

4

4

5

5

Sun (light

energy)



decomposition

heat released to environment

photosynthesis

feeding

feeding

respiration

respiration

respiration

excretion

excretion

egestion

egestion

Secondary

consumers

(carnivores)

Primary consumers

(Herbivores)

Producers (Green plants)Some heat is also lost to theenvironment during

decomposition.

Energy flow



1

2

3

3

4

4

4

5

5

+ CO2

Sun (light

energy)



decomposition


photosynthesis

feeding

feeding

respiration

respiration

respiration

excretion

excretion

egestion

egestion

Secondary

consumers

(carnivores)

Primary consumers

(Herbivores)


Energy flow



1

2

3

3

4

4

4

5

5

+ CO2CO2 Sun (light

energy)



decomposition


photosynthesis

feeding

feeding

respiration

respiration

respiration

excretion

excretion

egestion

egestion

energy lost in uneaten body

parts, faeces and excretory

products (usable energy)

heat lost to

environment

heat lost to

environment

Secondary

consumers

(carnivores)

Primary consumers

(Herbivores)


Energy flow



Energy flow• Energy flows from one trophic level to

another.

• The flow is non-cyclic as it does not return

to the organism which released it.

• It is lost mainly as heat.



Why are shorter food chains

more efficient than long foodchains?• Since energy is lost at each trophic level, less

and less energy is available for the organism atthe next level

• A shorter food chain means more energy isavailable to the final consumer because less

energy is lost to the environment• Most food chains have not more than 5 trophic

levels

Discuss with

your partner!



Energy flow• about 10% of light energy from the Sun is

stored in the plant tissues.

• If an animal eats the plant, only 10% of this

is used to build new animal tissues.

• The rest is used by the animal to stay alive,

keep warm and move about, and some islost in its faeces and urine.





Energy flow• Thus from one trophic level to another:

–Only 10% of the energy is transferred.

–Remaining 90% is lost.

• 10% is used to build new cell matter and

stored.



Energy flow



Energy flow1. Energy lost as heat to the environment

during respiration

2. Energy lost in faeces and excretory

products

3. Energy lost in dead organisms



Carbon Cycle• Carbon, oxygen, nitrogen & water are

essential nutrients for life.

• Nutrients are not lost to the environment

but are recycled instead.

• Nutrients are finite and thus, must be

recycled.

• Carbon cycle used as an example.http://www.epa.gov/climatechange/kids/movies/carbon_cycle_version

2.swf

http://www.epa.gov/climatechange/kids/movies/carbon_cycle_version2.swf







Carbon Cycle



Carbon Cycle• Photosynthesis:Carbon dioxide + water glucose + oxygen + water

Light energy

chlorophyll





Carbon CycleRelease of CO2 into the environment:

• Respiration of living organisms

• Combustion of fossils fuels

• Decay of dead organisms



Carbon Cycle Absorption of CO2 from the environment:

• Photosynthesis



Carbon Cycle• The cycle plays an important role in

maintaining a balanced amount of carbon

dioxide in the atmosphere.• What would upset this balance?

• What are some of the effects of such an

imbalance?



References• http://warnell.forestry.uga.edu/warnell/kahrs/h/habitats.html

• http://www.sheppardsoftware.com/content/animals/kidscorner/foodch

ain/producersconsumers.htm

• http://www.geographyalltheway.com/ib_geography/ib_ecosystems/imagesetc/food_web_300.gif

• http://www.epa.gov/climatechange/kids/movies/carbon_cycle_version

2.swf

• http://ez002.k12.sd.us/Chapter%20Two%20Science.htm

• http://www.ebi.ac.uk/2can/biology/organisms4.html

http://warnell.forestry.uga.edu/warnell/kahrs/h/habitats.html

http://www.sheppardsoftware.com/content/animals/kidscorner/foodchain/producersconsumers.htm


http://www.geographyalltheway.com/ib_geography/ib_ecosystems/imagesetc/food_web_300.gif




http://ez002.k12.sd.us/Chapter%20Two%20Science.htm

http://www.ebi.ac.uk/2can/biology/organisms4.html

http://www.ebi.ac.uk/2can/biology/organisms4.html

http://ez002.k12.sd.us/Chapter%20Two%20Science.htm







http://warnell.forestry.uga.edu/warnell/kahrs/h/habitats.html

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Ecology 3 - Food Chains Webs Energy Transfer

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