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Gateway Intervention
Shiloh High School
Energy Transformations in Biology
Respiration and Photosynthesis
• Photosynthesis
– Process of using energy from the sun to produce
sugars (glucose)
– 6CO2 + 6H2O + Light Energy  C6H12O6 +6O2
– Occurs in chloroplast of plants and some algae
– Photosynthesis produces all of the energy
available in most ecosystems.
• Some ecosystems that are not exposed to any sunlight
get their energy chemically.
Respiration and Photosynthesis
• Respiration
– Process of using energy from sugar (glucose) to produce
ATP
– C6H12O6 +6O2  6CO2 + 6H2O + 38ATP
– Occurs in mitochondria
– Occurs in both animals and plants
– ATP provides energy to do work in the cell
– When ATP is used, it is converted to ADP; respiration then
uses energy in sugars to convert ADP back to ATP by adding
a phosphate.
Respiration and Photosynthesis
• How are photosynthesis and respiration
related?
The products of respiration are the reactants
of photosynthesis; the products of
photosynthesis are the reactants of
respiration.
Respiration and Photosynthesis
• Where and how are excess sugars stored in
plants?
Excess sugars are stored as starch in the roots.
Starch is a polymer of glucose.
• Where and how are excess sugars stored in
animals?
Excess sugars are stored as glycogen in the liver
of animals. Glycogen is a polymer of glucose.
Flow of Energy Through an Ecosystem
• In order to live, organisms must obtain energy
and nutrients
– Heterotrophs
• Obtain energy and nutrients from the food they eat
– Autotrophs
• Obtain energy from the sun
• Obtain nutrients from the soil.
– Chemotrophs
• Obtain energy from chemical reactions, not the sun.
• Examples are the breakdown of rocks in caves (no
sunlight), and the breakdown of gases at undersea
vents (no sunlight).
Chemotrophs
• Chemoautotrophs (chemosynthesizers) are
bacteria that oxidize reduced inorganic substances
• (typically sulfur and ammonia compounds)
• and produce complex organic compounds.
oxygen
reduced
inorganic
compounds
chemoautotrophs
complex
organic
compounds
Chemosynthesis near hydrothermal vents
Flow of Energy Through an Ecosystem
• Producer
– Uses energy from the sun and carbon from the
environment to make its own food.
– “Bottom of the food chain”
– Why are producers necessary in any ecosystem?
Make energy from the sun available/usable for
heterotrophs.
Flow of Energy Through an Ecosystem
• Consumer
– Obtains energy through eating other organisms
• Herbivore: eats only plants
• Carnivore: eats only animals
• Omnivore: eats both plants and animals
– Primary consumer: eats producers
– Secondary consumer: eats the consumers that eat the producers
– Tertiary consumer: eats the consumers that eat the consumers
that eat the producers
– Means of obtaining nutrition
– Predation
» Ecological interaction in which one organism (predator) feeds
on another living organism(prey).
» Predator may or may not kill the prey.
– Scavenging
» An animal ingests dead plants, animals, or both.
» Vultures, termites, beetles
Decomposers
 Decomposer (Saprophytes)
• A type of comsumer
• Breakdown (absorb
nutrients from) non-living
organic material—
corpses, plants, waste of
living organisms—and
convert them to inorganic
forms.
» Bacteria, fungi
» Why are decomposers
necessary in any
ecosystem? Recycle
nutrients.
Flow of Energy Through an Ecosystem
Food Chain
• Linear pathway of energy transport through an
ecosystem (only one arrow goes to and from each link in
the chain).
• algaekrillcodsealkiller whalebacteria
• Producers always come first in the food chain.
• Decomposers always come last in the food chain; they
will break down dead organisms and allow nutrients to
be recycled.
• Arrows indicate the direction in which energy flows
through the ecosystem.
Trophic Levels and Food Chains
• The trophic level of an organism is
the position it occupies in a food
chain.
Carnivore
Carnivore
– Primary consumers include
insects and zooplankton
Tertiary
consumers
– Secondary consumers include
many small mammals, such as
rodents, and small fishes that eat
zooplankton
– Tertiary consumers, such as
snakes and bigger fish eat mice
and other secondary consumers
– Quaternary consumers include
hawks and killer whales.
Quaternary
consumers
Carnivore
Carnivore
Secondary
consumers
Carnivore
Carnivore
Primary
consumers
Zooplankton
Herbivore
Producers
Plant
A terrestrial food chain
Phytoplankton
A marine food chain
Flow of Energy Through an Ecosystem
Food Web
• A network of interconnected food chains in an
ecosystem
• Producers are at the beginning.
• Decomposers are at the end.
• Arrows indicate the direction in which energy
flows through the ecosystem.
Construct two distinct
food chains (different
starting and ending
points) from the food
web pictured with 4
organisms.
Practice:
• How does a food chain prove the Law of
Conservation of Matter and Energy?
The energy is not disappearing but is being
transferred from one organism to another.
Energy Pyramids
Energy Pyramid -a diagram that represents the
cumulative loss of energy from a food chain
There is a 90% decrease from
each trophic level to the next.
The Law of Conservation of
Energy states that matter can
not be created or destroyed.
Yet the energy pyramid shows
that less energy is available as
you move up a food chain.
Why is the Percentage of Energy Transfer
Between Trophic Levels so Low?
•
•
•
•
Not all of the organism is consumed.
Not all parts are digestible so they are excreted.
Some energy is lost in excretory substances.
Considerable heat is lost by respiration.
Conservation of Energy
Plant material eaten by
caterpillar
100 kilocalories (kcal)
35 kcal
50 kcal
Feces
15 kcal
Growth
Cellular
respiration
Pyramid of Biomass
Biomass is the total
weight of living matter at
a specific trophic level.
A pyramid of biomass
represents the total
weight of living material
available at each trophic
level.
The amount of biomass
decreases at higher
trophic levels.
Pyramid of Biomass
1 kilogram of
human tissue
10 kilograms
of beef
100 kilograms
of grain
Pyramid of Numbers
Fox (1)
Birds (25)
Grasshoppers
(250)
Grasses (3000)
Pyramid of Numbers
A pyramid of numbers
shows that populations
decrease at each
higher trophic level.
Population sizes
decrease in relation to
biomass, energy and
sustainability .
Carbon Cycle
• Carbon is the key ingredient in all living organisms
• Processes involved: biological (example: photosynthesis),
geochemical (example: release of CO2 by volcanoes),
human activity (example: burning of fossil fuels)
• Producers: Plants take in CO2 and make sugar by photosynthesis.
• Consumers: Animals eat plants to get energy (respiration) from
sugar and make proteins from the carbon.
– Breath out CO2 as a waste product of respiration.
• Animals die and decomposers break down the carbon and other
elements back into the soil and air for plants to use again.
Carbon Cycle
CO2 in
atmosphere
Photosynthesis
Burning
Producers
Wood and
fossil fuels
Cellular respiration
Higher-level
consumers
Primary
consumers
Decomposition
Bacteria
Detritus
Nitrogen Cycle
• All organisms require nitrogen to build
proteins
• Forms of nitrogen: N2 in atmosphere; NH3,
NO3-, NO2- in wastes; nitrate from fertilizers
• Some bacteria convert N2 into NH3 during
nitrogen fixation.
• Some bacteria convert nitrates into N2 during
denitrification.
Nitrogen Cycle
Water Cycle
• The never-ending circulation of the earth’s
water as it makes its long journey from the
oceans, to the air, to the land, and back to the
oceans again
• All organisms require water to survive.
• Processes: evaporation, transpiration,
condensation, precipitation, seepage, runoff
Water Cycle
Some Cool Water Facts
• How much water is on the earth?
– There are about 326 million cubic
miles of water. There are over a
million gallons of water per cubic
mile.
•How much water do living things contain?
-All living things consist mostly of
water. Humans are 60% water.
•What is the largest single use of water?
-The largest single use of water is by
industry. It takes about 80 gallons of
water to make the paper for one
Sunday newspaper.
•
How much of the earth’s water is fresh?
– Only about 3% of the earth’s water
is fresh. About 75% of the earth’s
fresh water is frozen in ice caps
and glaciers.
•How much water does a person use every
day?
-On average, each person in the United
States uses more than 100 gallons of
water a day in the home.
•Can water ever be used up?
-Water is used and reused over and
over again—it is never used up. Every
glass of water you drink contains
molecules of water that have been
used countless times before.