Chapter 47Chapter 47Ecosystems: A Summary

AP BiologySpring 2011

Nature of EcosystemsNature of Ecosystems

Ecosystem is the sum of the organisms residing there and the environment

Nature of EcosystemsNature of Ecosystems

Primary producer: plant that serves as an autotroph by harnessing sun’s energy

Consumer: animal or heterotroph that derives energy from consuming plants or other animals

Nature of EcosystemsNature of Ecosystems

Detrivore: animal that consumes debris and small bits of organic matter

Decomposer: eats wastes and remains of plants and animals

Nature of EcosystemsNature of Ecosystems

Minerals: increase and decrease in natural cycles

The organisms of an ecosystem develop trophic levels ◦Food chain represents

passage of energy from one trophic level to the next

Tropic LevelsTropic Levels

The Nature of Food WebsThe Nature of Food Webs

A food web is a complex interaction among species of the ecosystem ◦In a grazing food chain, the energy goes from

producers to consumers ◦In a detrital food chain, energy goes from

producers to detrivores to decomposers An alteration in one species of a food web

may affect many different organisms

Food WebFood Web

Energy Flow Through EcosystemEnergy Flow Through Ecosystem

Primary production: rate at which plants harness the sun’s energy◦Depends on availability of water and nutrients◦Is higher on land than water

Energy Flow Energy Flow Through EcosystemThrough Ecosystem

Biomass pyramid: used as a tool to represent dry weight of the organisms at each trophic level ◦Plants or producers make up the base of the

pyramid ◦Consumers make up the upper portion of the

pyramid with the largest carnivores at the very top

Energy Flow Through EcosystemEnergy Flow Through Ecosystem

Energy pyramid: shoes how energy is lost when transferred to each trophic level ◦Energy transfer in watery ecosystems is usually

more efficient than those on land

Biological MegnificationBiological Megnification

The effects of dangerous chemicals can become intensified as they move up the food chain ◦An insecticide called DDT resulted in the

deaths of birds and other animals Book “Silent Spring” by Rachel Carson, brought

this problem to public’s attention ◦Mercury from various industries enters the

water supply and becomes intensified in fish

Biogeochemical CyclesBiogeochemical Cycles

Biogeochemical Cycles: nutrients move through environmental stores and living organisms ◦Elements enter living portion of cycle by

becoming incorporated into plants◦Ex. Water, carbon, nitrogen, phosphorous

cycles

Water CycleWater Cycle

Water cycle: begins when water evaporates from bodies of water and transpiration occurs in plants ◦Water condenses in clouds and rains down ◦Water collects in watersheds, aquifers and in

groundwaterFuture water supply may be ocean

through utilization of a desalinization process to remove salts

Water CycleWater Cycle

Carbon CycleCarbon Cycle

Carbon cycle: most contained in earth’s crust◦Carbon in ocean is originally formed from shells

of small organisms ◦Crust lifts up eventually and becomes part of

land mass

Carbon CycleCarbon Cycle

Diffusion takes place between carbon in atmosphere and that in ocean

There is a loop-like current which delivers carbon dioxide to ocean reservoir

Carbon changes from between carbon dioxide and bicarbonate

Carbon CycleCarbon Cycle

Man adversely affects carbon cycle by releasing more carbon into air contributing to global warming

Greenhouse Gases and Climate Greenhouse Gases and Climate ChangeChange

Main gases that contribute to greenhouse effect are: carbon dioxide, water, nitrous oxide, methane, and chlorofluorocarbons

Suns heat is absorbed by earth’s surfaceSome of heat is reflected back into

atmosphere, but atmospheric gases send some heat back to earth

Greenhouse Gases and Climate Greenhouse Gases and Climate ChangeChange

Greenhouse effect: heat builds up in lower atmosphere, the air temperature near Earth’s surface rises ◦Natural necessary phenomenon to maintain

reasonable temperatures on earth ◦Increase in greenhouse gases is creating

abnormal global warming◦Global warming is causing warmer ocean

temperature which result in melting glaciers and more severe storms

Nitrogen CycleNitrogen Cycle

Nitrogen exists in atmosphere as N2 which is not in a usable form for plants ◦Some natural processes such as lightening and

volcanoes can convert the nitrogen to a usable form

Nitrogen CycleNitrogen Cycle

The bacteria Rhizobium that exists in nodules on legumes also converts the nitrogen to a usable form ◦Nitrogen changes from N2 to NH3 which then

converts to NH4+ and NO3

-, which are able to be used by plants

Nitrogen CycleNitrogen Cycle

Manmade interference helps to denitrify the ecosystem ◦The leaching of water through the soil and the

absence of crop rotation help to deplete the soil of nitrogen

When fertilizers run off into water sources, it causes algae blooms which are disadvantageous to animal species

Nitrogen CycleNitrogen Cycle

Phosphorous CyclePhosphorous Cycle

Phosphorous cycles between land and ocean◦Phosphates are necessary for major cellular

components like nucleic acids, plasma membranes and ATP

Phosphorous CyclePhosphorous Cycle

Plants get phosphorous from the water and soil

Animals get it from consuming plants or other animals ◦Phosphorous levels are quite often a limiting

factor for plant growth ◦Lock of phosphorous in soil can be due to

absence of crop rotation

Phosphorous CyclePhosphorous Cycle

An excess of phosphorous can result from water that runs off from fertilized fields ◦Excessive amounts of phosphorous in watery

environment can cause eutrophication◦Algae bloom occurs that harms plant and

animal species◦Difficult to reverse