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Chapter 47. Ecosystems. Bye-Bye Blue Bayou. READ PGs 842-843. Energy and raw materials in a physical environment organize the interactions among species in a community. Ecosystem: the organisms with their environment that interact by a flow of energy and resource cycle.

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Chapter 47


Bye-Bye Blue Bayou

READ PGs 842-843

Energy and raw materials in a physical environment organize the interactions among species in a community.

Ecosystem: the organisms with their environment that interact by a flow of energy and resource cycle.

The Nature of ecosystems

Although ecosystems vary in their climate, landforms, soil, vegetation, animal life, etc., all ecosystems have some similaries.

Overview of the participants

Run on energy from autotrophs (primary producers)

Consumers are heterotrophs that eat autotrophs (herbivores, omnivores, carnivores, parasites)

Detritovores eat particles of decomposing material.

Decomposers break down remains (bacteria, protists and fungi)

Trophic Levels

Most nutrients are taken up by autotrophs

Hydrogen, oxygen, carbon, phosphorous and nitrogen are all required for biosynthesis.

Decomposition of wastes and remains releases these nutrients back into the environment.

Sometimes the nutrients are lost to the ecosystem when they flow out in water.

Nutrient Cycles

Energy to ecosystems is in the form of sunlight.

Energy transfer is never 100 efficient.

Energy originally harnessed by producers escapes through metabolic heat and wastes that are not consumed.

10% of energy is transferred when energy moves up a trophic level.

Energy transfer



Primary consumer

Secondary consumer

Tertiary consumer



DDT is a relatively stable insecticide that is almost completely insoluble in water, but very soluble in fats.

Works as a nerve cell poison that takes 2-15 years to break down.

DDT accumulates in tissues of animals that come into contact with it.

The higher an animal’s trophic level is, the more DDT ends up in its tissues.

Read more about DDT on page 849.

DDT- A case of Biological Magnification

Primary Productivity- the rate at which producers store energy in their tissues during a given interval.

Net Ecosystem Production- Primary production minus energy used by producers and decomposers.

The harsher conditions are, the lower primary productivity.

Energy Flow Through Ecosystems

Biomass pyramids

Energy Pyramids

Biogeochemical cycles- the cycle of an essential element from the environment, through an ecosystem and back to the environment.

Oxygen, hydrogen, carbon, nitrogen, phosphorous.

Water provides hydrogen and oxygen and other elements that dissolve in it.

Biogeochemical Cycles

Hydrologic- oxygen and water move in water through an ecosystem

Atmospheric- a gaseous form of a nutrient moves through an ecosystem (carbon and nitrogen)

Sedimentary- elements with no gaseous form (solids) move through an ecosystem (phosphorous). Earth’s crust is reservoir for these nutrients.

Types of biogeochemical cycles

Cycle is driven by solar energy.

Water is driven from ocean atmosphere land ocean (main reservoir).

Many nutrients move into and out of ecosystems in water.

Watershed- a region where precipitation (rain, etc.) flows into a single stream or river.

Hydrologic Cycle

Our planet is facing a freshwater crisis.

Groundwater is easily contaminated by chemicals from landfills, hazardous waste dumps, gasoline, oil, sewage, toxins from power plants.

Water is also contaminated with pesticides, phosphates and other chemicals.

Desalinization uses huge amounts of fossil fuels.

We use more groundwater than the environment is replacing.

A global water crisis

Carbon Cycle

Main reservoir- earth’s crust

Carbon required for life’s quantity. All organic molecules are made of carbon.

Sometimes referred to as the carbon-oxygen cycle since CO2 is the main source of carbon for autotrophs.

Humans put 6 gigatons more carbon into the atmosphere than can be cycled back to the earth.

This carbon may be contributing to global warming.

Carbon cycle

Greenhouse Gases, Global Warming

Greenhouse gases (carbon dioxide, water, nitrous oxide, methane, chlorofluorocarbons) allow visible light from the sun to pass through them on the way to earth.

The earth’s crust absorbs the light and emits longer wavelengths in the form of heat.

The gaseous molecules do NOT allow the heat to pass through them, but absorbe the longer wavelengths and radiate them back to earth.

Nitrogen provides the quality of life. Carbon the quantity.

Nitrogen travels as N2 (two nitrogen atoms bonded with a triple covalent bond).

Most of our atmosphere is nitrogen!

Although volcanoes and lightening can split some nitrogen, most enters the food web through nitrogen fixation.

Bacteria are nitrogen fixers, converting N2 to ammonia (and later ammonium and nitrate), which plants easily take up.

Nitrogen cycle

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