Cycling of Material in an Ecosystem

• Important nutrients, and energy is cycled in ecosystems.

• Water cycle• Carbon cycle• Nitrogen cycle• Phosphorus

What four elements make up over 95% of most organisms?

• Oxygen• Carbon• Hydrogen• Nitrogen

Fig 9-3

Water Cycle

Water Cycle

• Transpiration – water enters the atmosphere by evaporating from the leaves of plants

• Precipitation – water enters the atmosphere as rain fall

• Evaporation – Water changes from liquid to gas• Condensation – Water changes from gas to liquid• Runoff- runs along surface and becomes ground

water.

Compass Activity Bi1341

• http://compass.rcschools.net/clologin.aspx

• Log on to Compass and enter the activity code for lesson.

Carbon Cycle• CO2 is taken up by plants during

photosynthesis• CO2 is released by organisms during

respiration and decomposition; fires, volcanoes • CO2 is also released by autos and

industries• carbon, present in all organic molecules,

moves through the food chain as one organism eats another

Carbon Cycle

Three large reservoirs where carbon is found in the biosphere.

• Atmosphere as CO2 gas

• Oceans as dissolved CO2

• Underground as coal petroleum, and calcium carbonate rock

There is much talk in the news about carbon emissions and high CO2 causing global warming.

Plants take up CO2 during photosynthesis.

Why don’t plants just take up all the extra CO2 and get it out of the atmosphere?

The Carbon Cycle

• How do the roles of autotrophs and heterotrophs differ in relation to the carbon cycle?

• Producers take in CO2 and consumers release CO2 during respiration.

• What are the human impacts on the cycle?• Fossil fuels – factories, vehicles, human activity• Volcanic activity also releases CO2 into atmosphere

Oxygen Cycle

• Essential for animals during respiration, released by plants

• Cycles much like the carbon cycle• What is threatening this cycle?• Forest deforestation, ocean pollution, etc

Nitrogen Cycle

Nitrogen Cycle• 78% of the volume of atmosphere• Most complex cycle• N2 gas can’t be used ‘as is’ – it must be ‘fixed’ so that organisms

can use it• Steps to the cycle: b/c of complexity, no certain order

– N Fixation – occurs in plant, by bacteria– Ammonification – Nitrification – Assimilation – Denitrification

• N2 gas is modified by “nitrogen-fixing” bacteria in legumes into ammonia (NH3) – NITROGEN FIXATION – aids in production of sugars/starches

• Denitrification is the process by which some soil bacteria convert nitrates into nitrogen gas.

Fig 3-19

Nitrogen fixation: Bacteria in root nodules of legumesAn example of mutualism

Nitrogen cycle (con’t)• Plant roots take up the ammonia and

nitrate ions and converts it into amino acids which are the building blocks of proteins

• nitrogen, present in proteins, moves through the food chain as one organism eats another

The Nitrogen Cycle• How and in what form(s) does nitrogen enter and leave

the cycle?• Bacteria through nitrogen fixation.• Decomposers return nitrogen to the soil as ammonia.• Bacteria convert nitrates into nitrogen gas through

denitrification.• Humans add fertilizer which contains nitrogen• Why is nitrogen important?• To make amino acids which build• PROTEINS!!!!

Nitrogen Cycle

Phosphorus Cycle

Phosphorus Cycle• phosphorus is released as rocks erode and

plants absorb the phosphorus• Very slow process• phosphorus passes from one organism to

another in the food chain • decomposers release phosphorus during

decomposition• Mined for production of fertilizer. Mined in

Tampa, FL

The Phosphorus Cycle

• How and in what form(s) does phosphorus enter and leave the cycle?

• From rocks and soil and enters through water and plants.

• Why is phosphorus essential to living organisms?

• DNA and RNA

Phosphorus Cycle

Limiting Nutrient

• A nutrient that is in short supply in an ecosystem and will slow growth.

• If a limiting nutrient is found in large supply it can cause an algal bloom to occur.

• Too much of the limiting nutrient will cause excessive and fast growth of organisms.

A bloom of Cyanobacteria

Cyanobacteria

Anabaena Microcystis

Fig 3-20

Nutrient cycling and energy flow through an ecosystem