Energy in Ecosystems
ALL LIVING THINGS USE ENERGY
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The earth is SOLAR POWERED!
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The source of all energy for ecosystems is
the Sun.
The Sun:
1) lights and warms the surface of the Earth
2) provides energy needed to evaporate water
from the oceans and lakes, to form rain and
snow
3) provides energy used by green plants to make
the compounds that maintain their lives and
serve as food for all organisms
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Of the energy that penetrates into the lower
atmosphere, about 30% is reflected by clouds or
the Earth’s surface.
The remaining 70% warms the surface of the
planet, causing water to evaporate, and
generating the water cycle and weather.
Only a very small portion (about 1%) of the
sun’s energy is actually used by green plants for
PHOTOSYNTHESIS.
Photosynthesis (1:59 min):
http://www.youtube.com/watch?v=LgYPeeABoUs&feature=related
Another song (1:52 min):
http://www.youtube.com/watch?v=C1_uez5WX1o&feature=related
Photosynthesis

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process by which green plants use sunlight to
produce carbohydrates (glucose/sugars)
trap light energy into chemical bonds of sugar
AUTOTROPHS = PRODUCERS
- make their own food
- main producers on land are
green plants and in water
they are algae

About 1% of
sunlight is
absorbed by
primary
producers
Photosynthesis
6CO2 + 6H2O + light energy
C6H12O6 + 6O2
carbon dioxide gas + water + sunlight
glucose + oxygen gas
Cellular Respiration

process plants use to obtain energy from
glucose
C6H12O6 + 6O2
6CO2 + 6H2O + energy
glucose + oxygen gas
carbon dioxide gas + water + energy
Adv. Cell Resp. song (4:54 min): http://www.youtube.com/watch?v=3aZrkdzrd04&feature=related
Adv. Glucose song (2:45 min): http://www.youtube.com/watch?v=jJvAL-iiLnQ&feature=fvw
Cellular Respiration

Plants use the energy released for all the
processes inside their cells as well as for
growth, repair of tissues and reproduction.

Animals also carry out cellular respiration to
release the energy but must obtain glucose by
eating food containing carbohydrates.
- Energy is used for movement, digestion,
growth, repair and reproduction.
Energy Movement in Ecosystems
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By categorizing living things by their
trophic (feeding) level in their ecosystem,
we can better understand how energy
flows
Energy flows through an ecosystem in a
series of steps in which organisms
transfer energy by being eaten
What happens to all the energy in
organisms at each level?
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90% of the energy is lost at each transfer,
most of it as heat
Only 10% of the energy that the animal
eats is able to be passed on to an animal
that eats it
We can take a look at this transfer
through:
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Food chains- simple model that shows
how matter and energy move through an
ecosystem
Food webs- shows all possible feeding
relationships in a community at each
trophic level
- Represents a network of interconnected
food chains
Food chains and Energy Song (2:46 min): http://www.youtube.com/watch?v=TE6wqG4nb3M
Calorie definition - a unit of heat equal to the amount of heat required to raise the temperature of one kilogram of water by one degree at one atmosphere pressure; used by
nutritionists to characterize the energy-producing potential in food
Food chain
(just 1 path of energy)
Food web
(all possible energy paths)
Definitions
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AUTOTROPHS = PRODUCERS
- make own food using photosynthesis
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HETEROTROPHS = CONSUMERS
- get energy from consuming other organisms
Other Heterotrophs/Consumers:
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HERBIVORES – eat only plants
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CARNIVORES – eat only animals
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OMNIVORES – eat both plants
and animals
Other Heterotrophs/Consumers
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DETRITIVORES – feed on plant
and animal remains
Examples: mites, earthworms,
snails, crabs, vultures
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DECOMPOSERS – break down
and absorb organic matter
Examples: bacteria and fungi
4th trophic level
3rd trophic level
2nd trophic level
1st trophic level
Energy/Trophic Levels
First Trophic level – producers/autotrophs
Second Trophic level – primary consumers, herbivores that
feed directly on producers
Third Trophic level – secondary consumers, primary
carnivore that relies directly on primary consumers
Fourth Trophic level – tertiary consumers, secondary
carnivore that relies directly secondary consumers
Keeps going…..