Biology 12

Matter and energy In most natural ecosystems, matter cycles and is re-used Energy flows and is lost At each trophic level most of the energy is lost in respiration

Water cycle Precipitation Transpiration Run off Evaporation Condensation Water uptake Surface water Ground water

Water cycle

Carbon cycle Air Fossil fuels Producers Consumers Decomposers Fossilisation Respiration Wastes Photosynthesis Combustion Respiration.

Carbon cycle

Nitrogen cycle Atmospheric Nitrogen Animal protein Plant protein Denitrifying bacteria Nitrifying bacteria Fertilisers and lightning Dead organisms & wastes Nitrogen fixers Ammonia Nitrates Root nodule bacteria

Nitrogen cycle

Phosphorus cycle Animals Plants Decomposers Soil and water Rocks Erosion Sedimentation

Phosphorus cycle

Energy in ecosystems Energy available from previous level Energy leaving as waste heat Energy used for new growth Respiration Energy lost in wastes

Measuring energy flow Sun outputs ~ kJ per day kJ per day is reflected and not used 2 000kJ per day is used by plants Heat energy lost due to respiration 1200 kJ 220 kJ 32 kJ Energy used for growth and thus available to next level 320 kJ40 kJ 480 kJ 60 kJ8 kJ 548 kJ Energy in dead matter and wastes

Measuring energy flow Productivity - rate at which an ecosystem accumulates mass or energy – biomass/unit area/time period (eg kg/m 2 /day) or energy/unit area/time period (eg kJ/m 2 /day) Biomass – dry weight of organisms found in a trophic level - mass/unit area (eg kg/m 2 ) or energy/unit area (eg kJ/m 2 ) Gross primary productivity – how much solar energy is fixed as chemical energy by producers (ie measure of energy trapped by photosynthesis Net primary productivity – amount of energy available once respiration has occurred

Pyramids These show numbers of organisms, or energy/mass available at each trophic level The 4 types are numbers, size, biomass and productivity

Drawing pyramids Trophic status OrganismNumber of organisms Size of organismBiomass (g Carbon/m 2 )New tissue produced (g/day) Producer15 m1506 1st order consumer 5005mm158 2nd order consumer 420 cm rd order consumer 401 mm number size biomass productivity producer 1 st order consumer 2 nd order consumer 3 rd order consumer 1 st order consumer producer 2 nd order consumer 3 rd order consumer <5000 mm <500 mm <50 mm <5 mm <1 mm

Short answer a & b The following diagram shows a food web occurring in a eucalypt woodland in Australia a) Is Acrida a plant or an animal? Using information the food web, explain your answer b) Which species, robin or ground beetles, will have the greatest biomass? Explain your answer by reference to the food web.

Short answer a The following diagram shows a food web occurring in a eucalypt woodland in Australia a)Is Acrida a plant or an animal? Using information the food web, explain your answer Most likely animal Feeds off gum trees Consumer/heterotroph (1 mark each) Wren (predator of Acrida) is a second order consumer Could be a parasitic plant

Short answer b The following diagram shows a food web occurring in a eucalypt woodland in Australia b) Which species, robin or ground beetles, will have the greatest biomass? Explain your answer by reference to the food web. Any four of: Probably ground beetles Robins eat ground beetles Robins convert some of the beetle biomass into heat Only about 10% of ground beetle biomass becomes robin biomass Ground beetles are a lower trophic level/lower in the food chain Can argue that robins eat earthworms as well as ground beetles, so their biomass may be more than would be expected on a diet of ground beetles alone.

Short answer c Indicate whether each of the following statements about the food web is TRUE or FALSE. Give a reason for each answer. (i) Energy is constantly lost from the food web. (ii) Some of the biomass in the ground beetles may eventually be found in the bodies of spiders.

Short answer c Indicate whether each of the following statements about the food web is TRUE or FALSE. Give a reason for each answer. (i) Energy is constantly lost from the food web. True - All organisms lose heat in respiration/metabolism/metabolic processes so energy is constantly lost. (ii) Some of the biomass in the ground beetles may eventually be found in the bodies of spiders. True - Beetles die, decompose and inorganic material/organic material/matter is recycled (possibly into spiders’ bodies)

Short answer d & e d) In some links in the food web, dozens, even hundreds, of species are grouped as one (eg mites). Give two reasons why this has been done. e) The gum trees in the community were sprayed with insecticide to reduce damage caused by gum moths. The insecticide is not harmful to vertebrate animals at the rate it was sprayed. There were no immediate impacts on other species, but after three months the frogmouths and quolls began to die. What might be causing their deaths?

Short answer d d) In some links in the food web, dozens, even hundreds, of species are grouped as one (eg mites). Give two reasons why this has been done. 2 marks/dot point in this question They occupy the same niche in the food web/consume the same food/have the same predators If all species were named the food web would be too complex Not all the species occurring in the food web will be known Only the most abundant species are shown

Short answer e e) The gum trees in the community were sprayed with insecticide to reduce damage caused by gum moths. The insecticide is not harmful to vertebrate animals at the rate it was sprayed. There were no immediate impacts on other species, but after three months the frogmouths and quolls began to die. What might be causing their deaths? Any four points from: Insecticide is concentrated along the food chain (biomagnification). Give two marks if the concept is described and biomagnification used, no marks if just biomagnification written. Each link in the food chain ingests a lot of the organism below it and accumulates all the pesticide in those organisms. Therefore the pesticide increases at higher levels in the food chain At the higher levels the accumulated pesticide becomes toxic The insecticide is not biodegradable.

Extended answer (c) Explain the concept of an ecosystem, describing the major components. Explain how ecosystems are interlinked to form a biosphere.

Extended answer (c) Explain the concept of an ecosystem, describing the major components. Explain how ecosystems are interlinked to form a biosphere. ecosystem is all organisms in an area and the physical environment with which they interact plant components (producers) described animal components (consumers) described role of decomposers non-living components described the energy source is the sun organisms and non-living surroundings are linked through nutrient cycling a fully annotated diagram including the above points (max 6 marks) Maximum 6 marks biosphere is all the ecosystems of the earth energy flows, nutrients cycle biomass pyramids can be used to show these relationships organisms are linked via food chains and food webs matter may flow between ecosystems organisms may move between ecosystems pollutants may move between ecosystems Maximum 6 marks

Extended answer (d) Humpback whales weigh up to 65,000 kg, about as much as 70 mid-size cars. They primarily eat small crustaceans called krill which they filter from the seawater using brush-like plates called baleen, located on each side of their upper jaw. The humpback whales are at the end of a very short food chain in which small autotrophs (phytoplankton) are the producers, krill are first order consumers and the whales are second order consumers. (i) From your knowledge of energy flow in ecosystems, suggest why humpback whales are able to grow so large. Extinct large sharks called Megalodon are believed to have preyed on primitive whales. (ii) Would the biomass of Megalodon have been larger, smaller or about the same as the biomass of its prey? Explain your answer.

Extended answer (d) Humpback whales weigh up to 65,000 kg, about as much as 70 mid-size cars. They primarily eat small crustaceans called krill which they filter from the seawater using brush-like plates called baleen, located on each side of their upper jaw. The humpback whales are at the end of a very short food chain in which small autotrophs (phytoplankton) are the producers, krill are first order consumers and the whales are second order consumers. (i)From your knowledge of energy flow in ecosystems, suggest why humpback whales are able to grow so large. all energy comes from the sun producers fix solar energy, but efficiency is low consumers gain energy from breaking down ingested organic compounds at each step in a food chain, only 10% of energy is transferred the longer the food chain, the less energy at the end biomass reduces at each step in a food chain the short food chain involving humpback whales means more energy at the end and more biomass can be sustained Maximum 6 marks

Extended answer (d) Humpback whales weigh up to 65,000 kg, about as much as 70 mid-size cars. They primarily eat small crustaceans called krill which they filter from the seawater using brush-like plates called baleen, located on each side of their upper jaw. The humpback whales are at the end of a very short food chain in which small autotrophs (phytoplankton) are the producers, krill are first order consumers and the whales are second order consumers. Extinct large sharks called Megalodon are believed to have preyed on primitive whales. (ii) Would the biomass of Megalodon have been larger, smaller or about the same as the biomass of its prey? Explain your answer. smaller biomass than the prey only 10% of the energy in the prey is transferred to the Megalodon 90% of energy is lost as heat if Megalodon had alternative prey to whales, then it might not have a smaller biomass than whales labelled food web indicating alternative food sources for Megalodon labelled biomass pyramid indicating lower Megalodon biomass Maximum 6 marks