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.