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Energy Flow In Ecosystems Notes
Producers
Consumers
Feeding Relationships
Ecological Pyramids
Producers
▪ Sunlight is the main source of energy for life on Earth
▪ Organisms that capture energy from sunlight or chemicals and use that energy to produce food are called autotrophs.– They make their own food
▪ Also called producers.
Producers▪ Plants use photosynthesis to
produce food from the energy they capture from the sun.
▪ Land - best autotrophs are plants
▪ Freshwater - best autotrophs are algae.
▪ Tidal Flats/Salt Marshes - Cyanobacteria (photosynthetic bacteria)
Producers▪ Some autotrophs produce
energy without light▪ Chemosynthesis: process
where organisms use chemical energy to produce carbohydrates.
▪ Performed by several types of bacteria– Volcanic vents in ocean– Hot springs– Tidal Marshes
Consumers▪ Many organisms -
animals, fungi, and many bacteria - can only acquire energy from other organisms.
▪ These animals are called heterotrophs.
▪ Also called consumers.
Types of consumers
Feeding Relationships▪ Energy flows through an ecosystem in
one direction, from the sun or inorganic compounds to autotrophs (producers) and then to various heterotrophs (consumers)
Food Chains▪ Food Chain: a series of
steps in which organisms transfer energy by eating and being eaten.
▪ Most ecosystems are complex, too complex to be represented in a food chain.
Food Webs▪ To represent the
complex feeding relationship in an ecosystem, food webs are used.
▪ Food webs link all food chains in an ecosystem together.
Food Webs
▪ Trophic Levels: each step in a food chain or food web.– Producers make up
the first level– Consumers make up
the second (secondary) , third (tertiary), or higher levels.
Ecological Pyramids▪ Amount of energy or matter in an ecosystem
can be represented by an ecological pyramid.▪ Ecological pyramid: diagram that shows the
relative amounts of energy or matter contained within each trophic level in a food chain or food web.
▪ Three types:– Energy pyramids– Biomass pyramids– Pyramids of Numbers
Energy Pyramids▪ Theoretically - no limit on
the number of trophic levels in an ecosystem.
▪ The Hitch - only about 10% of the energy available with one trophic level is transferred to organisms at the next trophic level.
▪ Summary - the more levels, the less energy that remains from the original
Biomass Pyramids▪ Biomass: the total
amount of living tissue in a given trophic level.– Represented in grams
of organic matter per unit area
▪ Shows potential food available for each trophic level.
Pyramids of Numbers
▪ Based on the number of individual organisms at each trophic level.
▪ Not the case for a forest ecosystem– In most forests, there
are fewer producers than there are consumers.
– Ex: Many insects live in one tree.