Energy Flow In Ecosystems
BIG IDEA:
WHAT HAPPENS TO ENERGY STORED IN
BODY TISSUES WHEN ONE ORGANISM EATS
ANOTHER?
Food Chains & Food Webs
 How does energy flow
through ecosystems?

A 1-way stream, from primary
producers to consumers
 Food Chains
 A series of steps in which
organisms transfer energy by
eating and being eaten
Food Chains & Food Webs
 Food Webs
 A network of feeding relationships; shows all the feeding
relationships within an ecosystem
Food Chains & Food Webs
 Food Webs –
 Very complicated

Notebook Time:
Describe the ecosystem that is your backyard
 Draw a food web of that ecosystem
 Be as specific as possible
 Draw a food chain from within your food web
 What role do decomposers & detritivores play in food webs?

Food Chains & Food Webs
 Disturbances
 In your groups, answer the following questions using the food
web below:
What effect would an insecticide have on the food web?
 Would this have an effect on the populations of non-insect eating
animals?
 What populations would increase?
 What populations would decrease?
 Would this change any animals
eating habits? Which ones & how?

Trophic Levels & Ecological Pyramids
 Trophic Level
 Each step in a food chain
 Ecological Pyramids
 Show relative amount of energy or matter contained within
each trophic level in a given food chain or food web
 There are 3 different types of Ecological Pyramids
Pyramids of Energy
 Pyramids of Biomass
 Pyramids of numbers

Ecological Pyramids
 Pyramids of Energy
 Show relative amounts of
energy available at each
trophic level
 Typically
1/10 or 10% of available
energy within one trophic
level is passed on to the
next level
 In other words:
 1/10 of the solar energy
captured and stored in
leaves of grasses ends
up stored in the tissues
of cows

Ecological Pyramids
 Pyramid of Biomass &
Numbers

Biomass –


Total amount of living
tissue within a given
trophic level
Pyramid of Biomass

Illustrates the relative
amount of living organic
matter available at each
trophic level of an
ecosystem
Ecological Pyramids
 Pyramid of Biomass &
Numbers

Pyramid of Numbers

Shows the relative number of
individual organisms at each
trophic level in an ecosystem
Cycles of Matter
 How does matter move through the biosphere?

Biogeochemical cycles
Elements pass from one organism to another and among parts of the
biosphere in closed loops
 These loops are powered by the flow of energy.


4 Processes involved with biogeochemical cycles
Biological Processes
 Any and all activities performed by living organisms
 Geological Processes
 Volcanic eruptions, erosion, plate tectonics
 Chemical & Physical Processes
 Formation of clouds, flow of running water, lightning
 Human Activity
 Deforestation, burning of fossil fuels, use of fertilizers

Water Cycle
Water moves continuously between, oceans, the
atmosphere, land and the organisms in them.
 Transpiration

Evaporation of water from leaves of the plants
 Evaporation
 Loss of water from surface of bodies of water
 Condensation
 When water vapor cools & becomes liquid
 Precipitation
 When water falls out of the atmosphere
Nutrient Cycles
 3 main Nutrient Cycles
 Carbon
 Nitrogen
 Phosphorus
Nutrient Cycles
 Carbon Cycle
 Found in several large reservoirs in biosphere
Atmosphere = CO2
 Oceans = Dissolved CO2
 Land = in organisms, soil & rocks
 Underground =
 Coal, Petroleum & Calcium Carbonate
 In Life = base of all organic molecules

Nutrient Cycles
 Nitrogen Cycle


Required to build proteins, DNA, RNA
Atmospheric Nitrogen

N2 = Non-usable form for most organisms
 Needs to be “fixed”
 Nitrogen Fixation
• Process of N2 being converted into ammonia, nitrates & nitrites by
bacteria
• Relatively small amounts of N2 can be fixed by Lightning

Denitrification
• When N2 is released by soil bacteria who use nitrates for energy

Fertilizer

Huge human influence in adding excess Nitrates & Nitrites into
aquatic ecosystems
 Can cause algal blooms
Nutrient Cycles
 Phosphorus Cycle
 Essential for creation of DNA, RNA
 Not very abundant in biosphere


Remains mostly on land in rock, soil, & sediments
As rock & sediments wear down, P is released to environment.
Nutrient Cycles
 Nutrient Limitation
 Limiting Nutrient


In Soil


The nutrient whose supply limits productivity
Typically Limiting Nutrients are:
 Ca, Mg, S, Fe, Mn, P, Fixed N,
In Ocean

Typically Limiting Nutrients are:
 Fixed N