Chapters 54 and 55 Energy Flow Essential Idea: Ecosystems require a continuous supply of energy to fuel life processes and to replace energy lost as heat.

Ecosystems Ecosystems are all of the organisms living in a community along with the abiotic factors with which they interact.

Ecosystems Ecosystems can be thought of as transformers of energy and processors of matter.

Ecosystems Grouping species into trophic levels allows us to follow the transformation of energy and the movements of chemical elements through the community.

Most ecosystems rely on a supply of energy from sunlight. Autotrophs make use of this sunlight energy by converting it to chemical energy through photosynthesis.Ecosystems

Autotrophs Autotrophs ultimately support all organisms and they are called primary producers.

Autotrophs Plants, algae and photosynthetic prokaryotes are the biosphere’s main primary producers. They synthesize sugars and other organic compounds from sunlight through a process called photosynthesis.

Primary Production Primary production is the amount of light energy converted to chemical energy during a given time. Huge amounts of solar energy hit the earth each day. Only a small proportion of this hits a primary producer.

Primary Production Of the light that hits a primary producer, only about 1% is converted into chemical energy.

Primary Production 170 billion tons of organic material is created each year.

Primary Production Gross Primary Production (GPP) is the total amount of carbon coming into an ecosystem. It is all of the light energy that is converted into chemical energy by photosynthesis in a given time period.

Primary Production Net Primary Production (NPP) is the amount of energy left over after the plant has used what it needs for survival. NPP = GPP - R NPP represents the storage of chemical energy available to consumers.

NPP NPP is always the total new biomass added in a given time. It is always calculated as dry weight. The standing crop refers to the total (dried) biomass of an ecosystem. Rain forests, estuaries, and coral reefs have a high net primary production.

Primary Production There are 2 main factors which control primary production: 1. Light limitations 2. Nutrient limitations

Primary Production The amount of light an ecosystem receives contributes to the amount of primary production that occurs. In water, primary production is limited by depth, on land it is limited by the amount of plants.

Primary Production For instance, in water the depth of light penetration controls production. More than half of the total solar energy is absorbed in the first meter of water. Light isn’t the only factor which controls primary production. The lack of a production gradient between the equator and the poles demonstrates this. Something else must be occurring.

Primary Production Nutrient limitations also play a role and must be overcome in order for a lake or ocean to increase its production. Nitrogen and phosphorous are the 2 elements that most limit marine production.

Primary Production The role nutrient limitations play in an ecosystem were first noticed and studied by David Schindler.

David Schindler He noticed that runoff from farms and yards added a lot of nutrients to lakes. He also documented the idea of eutrophication -- the increased numbers of cyanobacteria and excessive growth due to runoff which causes an overgrowth of plant life.

Eutrophication As a result of eutrophication, many fish and other animals die due to decreased levels of O 2 in the water.

David Schindler He conducted a lot of research on eutrophication. Discovered that phosphorous was the main limiter of cyanobacteria growth. He is the reason why phosphorous was removed from detergents and other water reform measures were adopted.

Heterotrophs Heterotrophs comprise the trophic level above the primary producer. These organisms feed on autotrophs. Herbivores are primary consumers. Carnivores eat herbivores and are secondary consumers. Carnivores that eat other carnivores are tertiary consumers and so on...

The various organisms in an ecosystem constitute a food chain. The chemical energy in carbon compounds flows through food chains by means of feeding. Food Chain

Energy Release As the organisms feed on the levels below it, they oxidize the carbon containing compounds by cell respiration.

Energy Release The energy is ultimately converted to heat and lost to the environment. Living organisms cannot convert heat to other forms of energy. The heat generated is lost from the ecosystem.

Detritivores As organisms die, they are decomposed by detritivores and their chemical elements become available to other organisms. The breakdown products are called detritus.

Secondary Production Secondary production is the amount of energy in a consumer’s food source that gets converted into biomass--it is the same as NPP. Most primary production is not consumed because consumers can only eat so much.

Trophic Efficiency This is the percentage of production transferred from one trophic level to the next. To see how much production is actually lost, we can look at trophic efficiency. The energy loss between the trophic levels restrict the length of the food chains and the biomass of the higher trophic levels.

Trophic Efficiency Trophic efficiencies are usually between 5-20%. So, they are 80-95% unproductive. Because of this, most food webs only have 4 or 5 trophic levels. This contributes to pyramids of numbers.

Trophic Efficiency Pyramids of numbers represent the number of individuals present at each trophic level.

Trophic Efficiency Pyramids of numbers represent the number of individuals present at each trophic level.