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Energy Flows
Roles in an Ecosystem
• Habitat – an area in an ecosystem where an organism or species lives
• Niche – the specific role an organism or species plays within a habitat
• Producers – a group of organisms that produce their own food through the process of photosynthesis
• Also called autotrophs
• Consumers – a group of organisms that obtain their nutrients from other organisms; also called heterotrophs
• Types of consumers
• Herbivores – only eats plants • Scavengers – feeds on dead organisms
• Carnivores – only eats animals
• Decomposers – breaks down dead plant
and animal matter and releases the
• Omnivores – eats both plants
nutrients into the soil
and animals
• Also called saprobes
Food Chains
• Matter cycles through an ecosystem
• Energy flows through an ecosystem • Never lost
• Lost as work and heat
• Food chain – the sequence of organisms feeding upon each other in an ecosystem
• Primary consumer – feeds on producers
• Secondary consumer – feeds on primary consumers
• Tertiary consumer – feeds on secondary consumers
• Quaternary consumer – feeds on tertiary consumers
• Top consumer – the last consumer in a food chain;
is not directly preyed upon
Trophic Levels
• Trophic levels – a distinct level of feeding within an ecosystem
• Some difficulties fitting all species into one level
Biology 11.3 – Energy Flows
Energy Flows
Food Webs
•
Food web – a group of two or more food chains that are intertwined
• Arrows show flow of energy
• If one species is removed, other species must change niche or suffer
• Ex) Alaskan kelp forests
Ecological Pyramids
• Ecological pyramid – an illustration of the energy, biomass, or numbers at each trophic level
• Pyramid of energy – an illustration of the
• Pyramid of numbers – an
• Pyramid of biomass – an
amount of energy in the bodies of organisms
illustration of the number of
illustration of the total mass of
at each trophic level
organisms feeding at each trophic
dry, organic matter at each
level
trophic level in a given unit of
• About 10% of energy is passed to the
area
next trophic level
• Each trophic level supports
fewer and fewer organisms
• About 90% is turned into work or heat
• Biomass – the mass of dry, organic matter in a given habitat
• Less biomass available at each trophic level
• Rapid consumption of producers in some marine ecosystems
• Rapidly reproducing producers support larger consumer population
• Leads to inverted biomass pyramid
Biology 11.3 – Energy Flows