F Ecosystems & Energy Flow By Ms Cullen

Terminology Try and define the following terms used when studying the environment.

Biosphere

Ecosystem Ecosystem

Biotic factors: these involve other living organisms

Abiotic factors:

Habitat

Producer (autotroph) Can you remember the balanced equation for photosynthesis? 6CO 2 + 6H 2 0 C 6 H 12 O 6 + 6O 2

Consumer (heterotroph)

Decomposer (saprotrophs) saprotrophs

Trophic Level

Food Chain and Food Web Food chains and food webs describe the feeding relationships between species in an ecological community. They graphically represent the transfer of material and energy from one species to another within an ecosystem. Food chains and food webs describe the feeding relationships between species in an ecological community. They graphically represent the transfer of material and energy from one species to another within an ecosystem. ecological communitymaterialenergy ecosystem ecological communitymaterialenergy ecosystem Organisms are connected to the organisms they consume by arrows representing the direction of biomass and energy transfer. Organisms are connected to the organisms they consume by arrows representing the direction of biomass and energy transfer. Organismsbiomass Organismsbiomass

Pyramids of Numbers Oak trees are very large, but caterpillars are very small. One oak tree can feed many caterpillars, but many caterpillars are needed to feed a blue tit, and many blue tits are needed to feed a sparrow hawk. Draw a pyramid of numbers for this food chain. It should look like this:

Pyramids of Biomass The dry mass of all organisms per unit area of ground (or water) is called biomass. The total biomass at a particular step in a food chain is always less than the total biomass at the step before it. The dry mass of all organisms per unit area of ground (or water) is called biomass. The total biomass at a particular step in a food chain is always less than the total biomass at the step before it. Note the large biomass of the one oak tree, compared with the small biomass of lots of caterpillars, indicated by the shape of the pyramid. Note the large biomass of the one oak tree, compared with the small biomass of lots of caterpillars, indicated by the shape of the pyramid. The wider the bar, the more biomass there is. Pyramids of biomass always have this shape (but pyramids of numbers can be any shape). The wider the bar, the more biomass there is. Pyramids of biomass always have this shape (but pyramids of numbers can be any shape).

The circle represents the producer. All of the stored energy in the body of the producer organism is eaten by the primary consumer. This circle represents the primary consumer. Only the stored energy is eaten by the secondary consumer. This circle represents the secondary consumer. Only a very small fraction (shown in green) of the producer's original energy is stored by the secondary consumer. This energy is taken into the body of the tertiary consumer.

Energy Flow in Food Chains As you can see from the previous diagrams, only about 10% of the energy which the plant used for growth is taken into the body of the carnivore. The second consumer uses some of this energy for its own body activities and some of the energy will be wasted. Therefore, the amount of energy available for the tertiary consumer is only 1% of the energy which the primary consumer gained from the plant. As you can see from the previous diagrams, only about 10% of the energy which the plant used for growth is taken into the body of the carnivore. The second consumer uses some of this energy for its own body activities and some of the energy will be wasted. Therefore, the amount of energy available for the tertiary consumer is only 1% of the energy which the primary consumer gained from the plant. As the energy is passed along the food chain much of it is either used or lost. Therefore there is a limit to the number of organisms in a food chain. The top carnivore is usually the third or fourth consumer. As the energy is passed along the food chain much of it is either used or lost. Therefore there is a limit to the number of organisms in a food chain. The top carnivore is usually the third or fourth consumer.

Look at the diagram from Feltham book that shows what happens to solar radiation in an ecosystem.

Pyramids of Energy Pyramids of energy show us the amount of energy transfer between each trophic level. Pyramids of energy show us the amount of energy transfer between each trophic level. It is measured in kJ per m 2 per year, as there are seasonal variations. It is measured in kJ per m 2 per year, as there are seasonal variations. Pyramids of energy include the initial transfer of energy from the sun. Pyramids of energy include the initial transfer of energy from the sun.

NB these figures are in Joules – convert to kJ

Productivity The Primary Productivity of an ecosystem is the rate at which biomass is produced per unit area by the producers. It can be divided into 2: The Primary Productivity of an ecosystem is the rate at which biomass is produced per unit area by the producers. It can be divided into 2: Gross Primary Production (GPP) is the amount of energy stored by the producers. Gross Primary Production (GPP) is the amount of energy stored by the producers. Net Primary Production (NPP) is the amount of energy in excess of what the producer requires for its own respiration (R) and is therefore available for the next trophic level. Net Primary Production (NPP) is the amount of energy in excess of what the producer requires for its own respiration (R) and is therefore available for the next trophic level. NPP= GPP – R Units are kJm -2 yr -1 Units are kJm -2 yr -1

Ecosystem Mean NPP (kJm -2 yr -1 ) Extreme desert 260 Open ocean 4700 Temperate grasslands Temperate deciduous forest Intensive agriculture Tropical rainforest Mean values for NPP in a range of ecosystems

Look at graphs and information on productivity and how it can be calculated per year.

Questions Answer exam Q’s on sheet. Answer exam Q’s on sheet. Complete worksheet ‘Year 13 Ecology’. Complete worksheet ‘Year 13 Ecology’. Complete Qs 2, 3 & 6 on P ‘Advanced Biology For You’. Complete Qs 2, 3 & 6 on P ‘Advanced Biology For You’.

OCR A2 textbook P Write notes/ summary on how we as humans manipulate energy transfer. Write notes/ summary on how we as humans manipulate energy transfer.

Changing Ecosystems Using your fieldwork notes and OCR A2 books P write notes on: How succession occurs (including terms pioneer and climax communities). How succession occurs (including terms pioneer and climax communities). The stages of succession on sand dunes. The stages of succession on sand dunes. Fieldwork methods for sampling eg quadrats and transects. Fieldwork methods for sampling eg quadrats and transects.

Recycling of Nutrients

The Carbon Cycle

The Carbon Cycle involves: Photosynthesis which converts atmospheric CO 2 into carbon compounds Photosynthesis which converts atmospheric CO 2 into carbon compounds Respiration from plants and animals Respiration from plants and animals Combustion of fossil fuels Combustion of fossil fuels Decomposition micro-organisms feed on carbon compounds in dead plant and animal material and release it as CO 2 during respiration Decomposition micro-organisms feed on carbon compounds in dead plant and animal material and release it as CO 2 during respiration Slow release of CO 2 from oceans where carbon is locked up in carbonates, in shells and rocks. Slow release of CO 2 from oceans where carbon is locked up in carbonates, in shells and rocks.

The Carbon Cycle

Carbon sinks The concept of carbon sinks is based on the natural ability of trees, other plants and the soil to soak up carbon dioxide and temporarily store the carbon in wood, roots, leaves and the soil.

The Nitrogen Cycle

Role of bacteria in the nitrogen cycle Decomposers (saprophytic bacteria) These bacteria convert organic nitrogen based compounds in dead tissue, faeces and urine into ammonium ions (NH 4 + ).

Role of bacteria in the nitrogen cycle Nitrifying Bacteria Convert ammonium into nitrates. This involves 2 types of bacteria. Nitrosomonas, found in soil, that oxidise ammonium compounds into nitrites Nitrosomonas, found in soil, that oxidise ammonium compounds into nitrites Nitrobacter, also found in soil, oxidise nitrites into nitrate ions. Nitrobacter, also found in soil, oxidise nitrites into nitrate ions. NH 4 + NO 2 - NO 3 - NH 4 + NO 2 - NO 3 - nitrosomonas nitrobacter nitrosomonas nitrobacter ammonium nitrite nitrate

Role of bacteria in the nitrogen cycle Nitrogen Fixing Organisms (diazotrophs) These reduce nitrogen gas to ammonia. These reduce nitrogen gas to ammonia. The process is catalysed by an enzyme called nitrogenase. The process is catalysed by an enzyme called nitrogenase. N 2 + 3H 2 2NH 3 N 2 + 3H 2 2NH 3 nitrogen hydrogen ammonia Only certain bacteria and cynobacteria can do this some such as Azotobacter live freely in soil. Others, such as Rhizobium, form root nodules on leguminous plants. Only certain bacteria and cynobacteria can do this some such as Azotobacter live freely in soil. Others, such as Rhizobium, form root nodules on leguminous plants.

Role of bacteria in the nitrogen cycle Denitrifying bacteria Convert nitrate ions to nitrites and then to nitrogen gas which escapes into the atmosphere. Convert nitrate ions to nitrites and then to nitrogen gas which escapes into the atmosphere. This usually occurs in anaerobic conditions, such as waterlogged soil. This usually occurs in anaerobic conditions, such as waterlogged soil. Denitrifying bacteria include Pseudomonas and Thiobacillus. Denitrifying bacteria include Pseudomonas and Thiobacillus.