1. UNIT: Ecology How does energy and matter cycle through an ecosystem?
Standard Element: SB4.b
Explain the flow of matter and energy through ecosystems by
Arranging components of a food chain according to energy flow.
Comparing the quantity of energy in the steps of an energy pyramid.
Explaining the need for cycling of major nutrients
(C, O, H, N,).

2. Matter and Energy Transfer in an Ecosystem
Matter (nutrients) are constantly cycled through an ecosystem
Energy from the sun enters an ecosystem through the producers.
Energy flows from the producers to the primary consumers, to the secondary consumers and to the tertiary consumers and eventually to the decomposers
Energy is either used, transferred or lost as heat, but cannot be cycled!

3. Food chains
A food chain is a simple model that shows how energy flows in 1 direction through an ecosystem.
Food chains always begin with producers
Producers (autotrophs, plants) can make their own food using photosynthesis

4. Food Webs
A food web is a complex model that shows how energy flows in many directions through an
ecosystem.
Food webs always begin
with producers on the bottom
Producers (autotrophs, plants)can make their own food using photosynthesis

5. Food Chains and Webs show:
Energy flows from the producers, to the primary consumers, then secondary consumers, then tertiary consumers
Arrows always point from prey to predator because it shows where energy is transferred to.
Trophic levels or feeding steps:
1st trophic level-Producers
2nd trophic level-Primary consumers
3rd trophic level- Secondary consumers
4th trophic level- Tertiary consumers

6. The Ecological Pyramids
1. Energy Pyramid
Shows the decrease of energy at each trophic level.
The total energy transfer up is about 10%
Not all food that is eaten can be digested
Some of the digested food is used as energy and some is lost as heat

7. The Ecological pyramids
2. Pyramid of numbers
Shows the number of organisms on each trophic level
Producers will always have the largest population size.
3. Biomass pyramid(living weight)
Shows the mass of organisms on each trophic level
Producers will always have the largest biomass

8. Nutrient Cycles in Ecosystems
Nutrients are constantly cycled through an ecosystem in order to maintain homeostasis.
Water Cycle: movement of water through an ecosystem
Evaporation: liquid to gas
Condensation: water vapor cools
and gets packed to form clouds
Precipitation: rain, snow, sleet,
hail
Transpiration: water released
from plants
Runoff: extra water collected in
rivers and streams

9. Carbon Cycle in Ecosystems
Carbon is most commonly found in the form of CO2 gas in the atmosphere
Carbon released in the atmosphere by…
Burning of fossil fuels
(Combustion)
Cellular respiration
Decomposition
Carbon is used by…
1. Photosynthesis

10. Nitrogen Cycle in Ecosystems
Organisms need nitrogen to make proteins but we cannot use the nitrogen in the air SOOOO……
We depend on bacteria to fix it for us!
Nitrogen fixation: bacteria living on the roots of plants absorb nitrogen in the atmosphere and convert it to a form that plants can use to make proteins
Denitrification: Bacteria release nitrogen back into the atmosphere
How do we get the nitrogen that
we need? We get nitrogen by either
eating the plants, or by eating the
consumer that ate the plants