Energy Flow in Ecosystems

1
Energy Flow in Ecosystems
2
Our Goals

• explain the roles of producers, consumers, and
  decomposers in ecosystems
• describe a pyramid of energy in terms of energy
  flow through an ecosystem
• describe the roles of photosynthesis and cellular
  respiration within a pyramid of energy
• compare photosynthesis and cellular respiration
  in terms of the reactants, products, and chemical
  equations

3
What do ecosystems need to do?

• Capture energy
• Transfer energy
• Cycle nutrients

We want to know how energy is produced and used
in the ecosystem
4
Food Chains

• is a single pathway of energy transfer through an
  ecosystem as organisms eat one another.
• Ex. Kelp urchin otter

5
Food Webs

• All organisms are connected to each other in a
  food web
• Plants absorb nutrients and
• grow
• Herbivores eat plants
• Carnivores eat herbivores
• Scavengers eat the dead
• Bacteria and fungi decompose dead tissue

http//www.bigelow.org/edhab/images/food_web.jpg
6
What are Trophic Levels?

• Trophic Greek for nutrition
• Feeding relationships (describe what the organism
  consumes as fuel)

7
Trophic Levels
Tertiary Consumer

• start with energy from the sun
• captured by primary producers, which are eaten by
  consumers
• food chains usually go up only 4 or 5 levels
• all levels connect to decomposers

Secondary Consumer
PrimaryConsumers
Primary Producers
Decomposers
8
Producers

• Are also known as ________________.
• Are able to ______________________________from
  sunlight or chemicals and use that energy to
  produce food.
• Include ____________________, ____________________
  ____, and ___________________.

9
Consumers

• Rely on other organisms for their energy and food
  supply (eat producers and other consumers)
• Also called ____________________.
• Include herbivores, carnivores, omnivores
• Also include detritivores such as mites,
  earthworms, snails and crabs and decomposers

10
Decomposers

• Include bacteria and fungi
• Get their energy from the remains (dead stuff)
  and wastes of organisms
• Help cycle nutrients to producers

11
Ecological Pyramid of Energy
1
100
100,000
1,000,000,000
12
Energy transfer is inefficient

• About 10 of energy is lost between trophic
  levels
• Where does the energy go? The cost of living!

13

• The amount of energy at each trophic level in
  proportion to the next level is called ecological
  efficiency
• Which organisms, in terms of ecological
  efficiency, would be the best for us to consume?
  

14
Photosynthesis

• The process that plants, algae, and
  photosynthetic bacteria use to convert energy
  from the sun
• ______________powers chemical reactions that
  convert _______________and water into
  ________________and carbohydrates

15
The balanced equation for photosythesis is...

• _____ ____ __________
• Note that if it werent for photosythetic
  autotrophs, the air wouldnt contain enough
  oxygen for you to breathe!

sunlight
16
What is this cellular respiration?

• The process that releases energy (ATP) by
  breaking down glucose and other food molecules in
  the presence of oxygen
• C6H12O6 _O2 _CO2_H20 ATP
• Gives off carbon dioxide, water and energy
• Which organisms need these?

17
Turn to your partner...

• How are photosynthesis and cellular respiration
  alike?
• How are they different?