Ecology:
Community
Interactions
Food Web Notes/2.0:
Energy and feeding relationships!
Terms to know…..
Producers
• A group of organisms that can use the energy
in sunlight to make food.
• Energy for all ecological systems begin with
producers.
• Also called Autotrophs
• Ex. Plants and Algae
Autotrophs
Consumers
• Organisms that do not make their own food
• They must consume other organisms in order to live.
• Also called heterotrophs.
• Ex. Rabbits, Deer, Mushrooms
Heterotrophs
Herbivores
• Consumers
– 2. Herbivores – eat ONLY plants
• Ex. – Cows, Elephants, Giraffes
Carnivores
• Consumers
– 3. Carnivores – eat ONLY meat
• Ex. – Lions, Tigers, Sharks
Omnivores
• Consumers
– 4. Omnivores – eat BOTH plants and animals
• Ex. – Bears and Humans
Decomposers
• Consumers
– 5. Decomposers – absorb any dead material and break it
down to return nutrients to the earth.
• Ex. – Bacteria and Mushrooms
Trophic (energy) Levels
• Energy moves from one organisms to another when it is
eaten.
• Each step in this transfer of energy is know as a trophic
level
– The main trophic levels are producers, consumers and
decomposers
• Food chains show how energy moves from one
level to another. Arrows show energy flow.
Food Chain
Food Web
• Most organisms eat more the JUST one organism!
When more organisms are involved it is know as a
FOOD WEB.
• Food webs are more complex and involve lots of
organisms.
Food Web examples
Food Web Activity /
Not in Notebook
• Complete Part A of the Food Web Activity
– Work as a table group.
– Follow instructions on the plastic sheet.
– There are LOTS of correct ways to create this food
web 
– 25 minutes
Transfer of Energy
• No organism EVER receives all of the energy from
the organism they just ate. Why?
– Energy is lost as heat
– Not all of the organism is eaten
• Only 10% of the energy from one trophic level is
transferred to the next – this is called the 10% law
• As energy moves through a food web it
________________.
Ecological Pyramid
Ecological Pyramid
Ecological Pyramid
5. Which level has the most energy?
6. Which level has the most organisms?
7. Which level has the least organisms?
8. Which level has the least energy?
Food Web Activity
• Complete Part B of the Food Web Activity
– 15 minutes
Symbiosis
• A close and permanent association between
organisms of different species (not predator /prey)
• Chart
– Commensalism – a relationship in which one organism
benefits and the other is not affected
• Example: Barnacles on a whale
– Mutualism – a relationship in which both organisms benefit
from each other
• Example: Birds eating pest off a rhino’s back
– Parasitism – A relationship in which one organism benefits
and the other is harmed
• Example: Ticks on a dog
Cycling through the ecosystem
1. Water Cycle
– 4 –tions: evaporation, transpiration, condensation,
precipitation
– Powered by the Sun
– Abiotic Cycle
Cycling of resources in an ecosystem.
2. Carbon Cycle
• Write the equation for photosynthesis.
• Write the equation for respiration.
– How does carbon ENTER the atmosphere?
– How is carbon REMOVED from the atmosphere?
– Biotic Cycle
Carbon
Cycling of resources in an ecosystem.
3. Nitrogen Cycle
All living things need nitrogen!
• Lots of nitrogen is available in the air but plants cannot take it
in.
• Bacteria in the soil or on roots create usable nitrogen for
plants.
• Animals eat plants
• Death and decay puts nitrogen back into the air.
• Biotic Cycle
Diagrams
• Paste both diagrams in your notebook with the
notes.
• On the Carbon Cycle:
– Color the arrows that PUT Carbon Dioxide into the air
RED.
– Color the arrows that TAKE Carbon Dioxide out of the air
GREEN.
– What parts of the Carbon Cycle would not have been
present before the Industrial Revolution?
Water
Carbon
Nitrogen
Into the
atmopshere
Out of the
atmosphere
Biotic or Abiotic
Important
Organisms
Color ONE of the cycles on your
sheet.
Predator/Prey Interactions
(Homework Sheet)
Cycling of resources in an ecosystem.
• Water Cycle
– 4 –tions: evaporation, transpiration, condensation,
precipitation
– Abiotic Cycle
• Carbon Cycle
– How does carbon enter the atmosphere?
– How is carbon removed from the atmosphere?
– Biotic Cycle
• Nitrogen Cycle
– Bacteria in the soil or on roots create usable nitrogen for
plants.
Biomass
• The total mass of the organic matter at each trophic
level is called biomass
• Biomass is just another term for potential energy –
energy that is to be eaten and used.
• The transfer of energy from one level to another is
very inefficient (10% Law)
Biomass
Ecological Pyramid
• An ecological pyramid shows the relationship
between consumers and producers at different
trophic levels in an ecosystem
• Shows the relative amounts of energy or matter
contained at each trophic level
• The Pyramid shows which level has the most energy
and the highest number of organisms