IGCSE BIOLOGY SECTION 4 LESSON 3

Content Section 4 Ecology and the Environment a)The organism in the environment b)Feeding relationships c)Cycles within ecosystems d)Human influences on the environment

Content Lesson 3 c) Cycles within ecosystems b) Cycles within ecosystems 4.8 describe the stages in the water cycle, including evaporation, transpiration, condensation and precipitation 4.9 describe the stages in the carbon cycle, including respiration, photosynthesis, decomposition and combustion 4.10 describe the stages in the nitrogen cycle, including the roles of nitrogen fixing bacteria, decomposers, nitrifying bacteria and denitrifying bacteria (specific names of bacteria are not required).

Recycling

Paper Plastics cardboard Oil Bottles Aluminium cans Electrical items Food scraps

Recycling PRODUCERSDECOMPOSERS CONSUMERS SOIL

Recycling PRODUCERSDECOMPOSERS CONSUMERS SOIL Die Eaten Decay Water and nutrients

Recycling PRODUCERSDECOMPOSERS CONSUMERS SOIL Die Eaten Decay Water and nutrients Water, carbon and nitrogen cycles – ‘natural recycling’

The water cycle

evaporation

The water cycle evaporation transpiration

The water cycle evaporation transpiration condensation

The water cycle evaporation transpiration condensation precipitation

The carbon cycle Carbon – occurs in all compounds which make up living organisms. Plants get their carbon from carbon dioxide in the atmosphere and animals get their carbon from plants.

The carbon cycle

Carbon dioxide photosynthesis

The carbon cycle Carbon dioxide photosynthesis Dead organisms and waste products Decay organisms Organic carbon Decomposition Fossils and fossil fuels

The carbon cycle Carbon dioxide photosynthesis Dead organisms and waste products Decay organisms Organic carbon Animal respiration Plant respiration Root respiration Decomposition Fossils and fossil fuels

The carbon cycle Carbon dioxide photosynthesis Dead organisms and waste products Decay organisms Organic carbon Animal respiration Plant respiration Root respiration Decomposition Combustion – burning of fossil fuels Fossils and fossil fuels

The carbon cycle Carbon dioxide Photosynthesis Decomposition Respiration Combustion The nitrogen cycle When an animal or plant dies, its tissues decompose, partly as a result of bacteria action. One of the important products of this decay is ammonia (NH 3 ) which is washed into the soil. The excretory products of animals contain nitrogenous waste products such as ammonia, urea and uric acid.

The nitrogen cycle Key words: Nitrogen fixing bacteria Denitrifying bacteria Nitrifying bacteria Decomposers

The nitrogen cycle Nitrogen in the air Nitrogen-fixing bacteria in the soil. Nitrogen –fixing bacteria in root nodules of peas, clover Ammonium and nitrates in the soil Plant protein Animal protein Animal waste Dead animals and plants Nitrifying bacteria Denitrifying bacteria (in waterlogged soil) Decomposers

The nitrogen cycle Nitrogen in the air Nitrogen-fixing bacteria in the soil. Nitrogen –fixing bacteria in root nodules of peas, clover

The nitrogen cycle Nitrogen in the air Nitrogen-fixing bacteria in the soil. Nitrogen –fixing bacteria in root nodules of peas, clover

The nitrogen cycle Nitrogen in the air Nitrogen-fixing bacteria in the soil. Nitrogen –fixing bacteria in root nodules of peas, clover Ammonium and nitrates in the soil

The nitrogen cycle Nitrogen in the air Nitrogen-fixing bacteria in the soil. Nitrogen –fixing bacteria in root nodules of peas, clover Ammonium and nitrates in the soil Plant protein

The nitrogen cycle Nitrogen in the air Nitrogen-fixing bacteria in the soil. Nitrogen –fixing bacteria in root nodules of peas, clover Ammonium and nitrates in the soil Plant protein Animal protein

The nitrogen cycle Nitrogen in the air Nitrogen-fixing bacteria in the soil. Nitrogen –fixing bacteria in root nodules of peas, clover Ammonium and nitrates in the soil Plant protein Animal protein Animal waste Dead animals and plants Nitrifying bacteria

The nitrogen cycle Nitrogen in the air Nitrogen-fixing bacteria in the soil. Nitrogen –fixing bacteria in root nodules of peas, clover Ammonium and nitrates in the soil Plant protein Animal protein Animal waste Dead animals and plants Nitrifying bacteria

The nitrogen cycle Nitrogen in the air Nitrogen-fixing bacteria in the soil. Nitrogen –fixing bacteria in root nodules of peas, clover Ammonium and nitrates in the soil Plant protein Animal protein Animal waste Dead animals and plants Nitrifying bacteria Denitrifying bacteria (in waterlogged soil) Decomposers

The nitrogen cycle Nitrogen in the air Nitrogen-fixing bacteria in the soil. Nitrogen –fixing bacteria in root nodules of peas, clover Ammonium and nitrates in the soil Plant protein Animal protein Animal waste Dead animals and plants Nitrifying bacteria Denitrifying bacteria (in waterlogged soil) Decomposers High temperature lightning discharges cause some of the oxygen and nitrogen in the atmosphere to combine and form nitrogen oxides. These dissolve in the rain and are washed into the soil as weak acids, where they form nitrates.

The nitrogen cycle Nitrogen in the air Nitrogen-fixing bacteria in the soil. Nitrogen –fixing bacteria in root nodules of peas, clover Ammonium and nitrates in the soil Plant protein Animal protein Animal waste Dead animals and plants Nitrifying bacteria Denitrifying bacteria (in waterlogged soil) Decomposers

The nitrogen cycle Key words: Nitrogen-fixing bacteria Bacteria which can absorb nitrogen as a gas from air spaces in the soil and build it into compounds of nitrogen Decomposers Nitrifying bacteria Denitrifying bacteria

The nitrogen cycle Key words: Nitrogen-fixing bacteria Bacteria which can absorb nitrogen as a gas from air spaces in the soil and build it into compounds of nitrogen Decomposers Organisms which break down dead animal and plant material, releasing the nutrients into the soil. Nitrifying bacteria Denitrifying bacteria

The nitrogen cycle Key words: Nitrogen-fixing bacteria Bacteria which can absorb nitrogen as a gas from air spaces in the soil and build it into compounds of nitrogen Decomposers Organisms which break down dead animal and plant material, releasing the nutrients into the soil. Nitrifying bacteria Bacteria which convert ammonium compounds into nitrates. Denitrifying bacteria

The nitrogen cycle Key words: Nitrogen-fixing bacteria Bacteria which can absorb nitrogen as a gas from air spaces in the soil and build it into compounds of nitrogen Decomposers Organisms which break down dead animal and plant material, releasing the nutrients into the soil. Nitrifying bacteria Bacteria which convert ammonium compounds into nitrates. Denitrifying bacteria Bacteria that use nitrate ions in their metabolism and release nitrogen gas

End of Section 4 Lesson 3 In this lesson we have covered: Recycling in natural ecosystems The Water Cycle The Carbon Cycle The Nitrogen Cycle