Published byAnthony Haraway Modified over 8 years ago
The Cycling of Matter To understand how matter cycles through ecosystems, you must understand the cycling of organic substances in living things. The materials stored in living things comes from a limited amount of matter. Therefore, all matter must be recycled. This recycling of matter involves the carbon, oxygen and nitrogen cycles as well as the role of decomposers. All matter tied up in the bodies of organisms must be decomposed and recycled.
organic substance- compound that always contains carbon and hydrogen atoms, and often oxygen and nitrogen atoms. e.g. proteins, sugars, e.g. C6H12O2, CH4 inorganic substance - compounds that don’t contain a combination of hydrogen and carbon. e.g. CO2 , H2O
Carbon Cycle carbon is the main atom of all living things. In inorganic form it mainly exists as carbon dioxide gas in the air. CO2 is also dissolved in sea water. plants use carbon during photosynthesis to make carbohydrates. This takes carbon from its inorganic state and transforms it into organic compounds. This carbon then gets passed up the food chain carbon is returned to its inorganic state when organisms digest food to get energy. Consumers use sugars in a cell reaction process called cellular respiration.
Cellular respiration requires oxygen
Cellular respiration requires oxygen. This reaction releases energy to the body and gives off inorganic carbon dioxide to the air. Decomposer organisms also release carbon dioxide to the air some carbon has become buried as coal. This carbon is locked away out of circulation unless humans release it by burning fossil fuels (gas, oil, coal). These fossil fuel deposits, the ocean and boglands are huge reservoirs of carbon which are released slowly to the atmosphere.
Human Impact on the Carbon Cycle;
the level of CO2 in the atmosphere is rising quickly way beyond normal levels. This is due to: 1. carbon released from natural reservoirs faster than normal due to burning of fossil fuels, burning forests. 2. less CO2 being removed due to removal of plants to clear land for agriculture, forestry or building. The result has been global warming
global warming - a warming trend in our climate caused by excess greenhouse gases such as carbon dioxide. Greenhouse gas - any atmospheric gas that traps heat and adds to the greenhouse effect. e.g. carbon dioxide. CO2 in the atmosphere provides a natural “greenhouse effect”. It traps reflected solar energy and warms the earth. However, since humans have increased the amount of CO2 in the atmosphere, we are causing too much heat to be trapped and it is changing our weather patterns and climate. The average global temperature is rising.
Your Turn Do questions p. 65, # 1, 2, 4, 6, 7 (a) (b) (c)
The Nitrogen Cycle Nitrogen is needed by all organisms to make proteins (tissue) and DNA. 79 % of the air is nitrogen gas but plants and animals cannot get their own nitrogen from the air. Only plants can use inorganic forms of nitrogen such as nitrates, NO3 , found in the soil or dissolved in water, and extract - the nitrogen in them to use in making their own plant proteins. All consumers must consume other organisms to get their proteins. When organisms die, the nitrogen present in the proteins of living things gets recycled back into inorganic forms such as ammonia, nitrites and nitrates by the processes of decomposition and denitrification.
Nitrogen - fixation stage
nitrogen fixation - the process of converting free atmospheric nitrogen into nitrates. Nitrogen gas in the atmosphere gets converted into nitrates, NO3 . These are absorbed by the - roots of plants. This can occur in two ways: (1) lightning in the atmosphere - causes nitrogen in the air to react with oxygen to form nitrates. (2) Nitrogen - fixing bacteria - give off nitrates as a waste product. Some nitrogen fixing bacteria are free - living but many live in the roots of certain plants called legumes. They supply the legume plants with a steady supply of nitrogen in return for shelter in the roots and food. Legumes include beans, alfalfa and clover - type plants
Man’s Impact on the Nitrogen Cycle;
We are adding extra nitrogen to many environments in the form of fertilizers and pollution wastes from many industries. Human sewage is often released into rivers with little treatment(e.g. Montreal into the St. Lawrence River) and act as fertilizer. Normally, there is a balanced amount of nitrate in an aquatic ecosystem. However, in areas near agricultural lands where lots of fertilizers are used, runoff into rivers have caused the levels of nitrate in lakes to get too high.
this causes a process called eutrophication - pollution making a lake richer in nutrients.
If the level of nitrate gets too high, an algal bloom can occur. This is where the algae population grows out of control, scumming over much of the lake’s surface. The algae, too many in number, block much of the light from reaching other plants growing underwater. Also, when the algae die, the decomposer bacteria in the water have lots of food. This causes their population to increase.
All this extra decomposition uses up much of the dissolved oxygen in the water. This is very unhealthy to the ecosystem. It has a bad effect on many species, causing their numbers to decline. Fish and other aquatic animals may begin to die.
Decomposition stage Decomposer bacteria decay dead organisms. They break down the proteins in the dead organisms to produce ammonium. Other bacteria in the soil convert ammonium into nitrites. Another type of bacteria convert the nitrites into nitrates, becoming available again for plant use.
Some of the nitrates in the soil is converted back into free nitrogen gas by certain bacteria called denitrifying bacteria. This returns nitrogen to the atmosphere.
Your Turn Do -questions, p. 69, # and p. 71, # 3,4
The Oxygen Cycle Oxygen is cycled between the atmosphere and living (biotic) things. Oxygen is used in the process of cellular respiration by both plants and animals. Carbon is released in the form of CO2 as a waste product of this reaction. Plants take in the inorganic gas CO2 and use it in the process of photosynthesis to make organic sugars such as glucose, C6H12O6. Oxygen is released as a waste product of the photosynthesis reaction. The reactions of cellular respiration and photosynthesis are reciprocals of each other. The reactants of one reaction are the products of the other reaction.
CO2 (g) + H2O (l) → C6H12O6 (s) + O2 (g)
Photosynthesis: CO2 (g) + H2O (l) → C6H12O6 (s) + O2 (g) Cellular Respiration: C6H12O6 (s) + O2 (g) → CO2 (g) + H2O (g)
C6H12O6 (s) + O2 (g) → CO2 (g) + H2O (g)
Reaction Reactants Products Photosynthesis Carbon dioxide + water CO2 + H2O glucose sugar + oxygen C6H12O6 + O2 Respiration
Human Impact on the Oxygen Cycle
Deforestation is the major impact by man. Trees are the earth’s largest oxygen – producing plants. Plants give off O2 to the atmosphere through photosynthesis. The destruction of forests lowers the amount of CO2 which is being converted into O2. The reduction in trees is a one of the contributing factors to global warming.
Your Turn Case Study : The Effects of Deforestation on Cycling
p do items (b) - (g). p. 73, #
The Biomes of Canada (read pp. 88 - 92)
Biome - a collection of ecosystems that are similar or related to each other, usually by the types of plants present in the area.
There are 4 biomes present in Canada:
1. Tundra 2, Boreal Forest 3. Temperate Deciduous Forest 4. Grasslands
Tundra p. 88 - Know Table 1, p. 89 Also: - permafrost and active layer
- why no trees grow there - dominant plants? - why slow decomposition rate? - why few animal species are present
Boreal Forest Biome - know table 2, p. 90 - Also:
- dominant plants : conifers ( needle - leafed trees which produce cones) eg. spruce, fir,pine. p makes up 80% of forests in Canada - explain why soils are acidic here - explain how conifers are adapted to the extreme climate here p explain why food available in this to animals living in the lower layer of this biome is limited
Temperate Deciduous Biome: pp. 91 - 92
p know Table 3, p. 92 p know where its located p why is there faster decomposition here than in the Boreal? p Why do more plants grow under the large trees of this biome than in the Boreal? p Why can the temperate deciduous forest support more many more animals than the Boreal forest? p Describe the layers present in the temperate deciduous forest. Compare this to the Boreal Forest.
Grassland Biome: p Why does the temperate deciduous forest contains greater biodiversity than the Boreal forest? p know Table 4 p Grasslands are at a similar latitude as the Temperate deciduous forests but are different in terms of their dominant plants. Explain why. p Explain why trees don’t tend to grow on the grasslands. p Explain why the grassland soil is the most fertile soil in the world. p Explain why the biodiversity of grasslands is low in comparison to the Temperate Deciduous forest and the Boreal forest. DO: questions, p # 1 - 5, 8
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