Energy Flow
• Sunlight is the MAIN source of energy for all life on
Earth
• Only plants, some algae, and certain bacteria can
capture energy from the sun and convert it into a
USABLE form of energy
• Autotrophs – organisms that capture and convert the
sun’s energy
• Also called PRODUCERS!
• Producers use a process
known as photosynthesis
• Light energy is used to
convert carbon dioxide
(CO2) and water (H2O) into
oxygen (O2) and
carbohydrates (C6H12O6)
Carbon Dioxide + Water + Sunlight
Carbohydrates + Oxygen
• Some autotrophs can produce food without light by using
a process called chemosynthesis
• Chemical energy is used to convert hydrogen sulfide
(H2S), carbon dioxide (CO2), and water (H2O) into
carbohydrates (C6H12O6) and sulfur compounds (H2SO4)
• This usually occurs in remote locations (e.g. ocean floor
and hot springs)
• Bacteria are the most common autotrophs that use
chemosynthesis
• Photosynthesis
• “photo-” means “light”
• Uses light for energy
• Chemosynthesis
• “chemo-” means “chemicals”
• Uses chemicals for energy
• Many organisms cannot use sunlight as food
• Animals, fungi, some bacteria, some protists
• These organisms must consume other organisms to obtain energy
• These organisms are called heterotrophs
• Also called CONSUMERS!
•
Five (5) main types of heterotrophs:
1) Herbivore – consumes only plants
2) Carnivore – consumes only animals
•
Some scavengers are considered carnivores
3) Omnivore – consumes plants and animals
4) Detritivores – consumes decaying and rotting material (such as
rotting leaves, etc.)
•
Some scavengers are considered detritivores
5) Decomposers – breaks down organic (living) material
•
Finishes the job that scavengers and detritivores start
• Energy flows through an ecosystem in one direction
Sun/ Inorganic
Compounds
Autotrophs
Heterotrophs
• Food Chain – series
of steps in which
organisms transfer
energy by eating
and being eaten
• Shows one-way flow of
energy in an ecosystem
• Most feeding relationships are more complicated than a food
chain
• Food Web – network of complex interactions and feeding
relationships in an ecosystem
Marine Food Web
Terrestrial Food Web
• Trophic Levels – steps in the food chain/web
• Producers – 1st trophic level
• Consumers – 2nd, 3rd, or higher trophic levels
• Each consumer depends on the previous trophic level
5th Trophic
Level
4th Trophic
Level
5th Trophic
Level
4th Trophic
Level
3rd Trophic
Level
3rd Trophic
Level
2nd Trophic
Level
2nd Trophic
Level
1st
1st Trophic
Level
Trophic
Level
• Ecological Pyramid – diagram that shows the relative
amount of energy or matter contained within each
trophic level of a food chain/web
• 3 Types
• Energy Pyramid – shows the relative amount of energy available at
each trophic level
• Biomass Pyramid – shows the amount of living organic material at
each trophic level
• Pyramid of Numbers – shows the relative number of individual
organisms at each trophic level
• Only part of the energy that is stored at one trohpic level can
be passed to the next trophic level
• 10% of the energy at one level is transferred to the next
• Why isn’t ALL the energy transferred to the next level?
• The other 90% is used by the organism at the previous level
Light or Chemical
Energy
• Biomass – total amount of living tissue within a given trophic
level
• Usually expressed in terms of grams of organic matter per unit area
• Biomass pyramid represents the amount of potential food
available for each trophic level in an ecosystem
10 %
10 %
10 %
10 %
• Based on the actual number of individuals at each trophic level
• Does not always resemble the shape of a pyramid
• Ex: tree may be at bottom of “pyramid”