3. (a) CIRCULATION IN ECOSYSTEMS 1. Energy (Energy fixation & Energy flow) 2. Circulation of nutrients (Decomposition, Nutrient Cycling – N & Ph Cycles)
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13. Energy in an Ecosystem FLOWS from the SUN to Autotrophs (Producers) then to Heterotrophs (Herbivores) that eat the Autotrophs, then to Heterotrophs (Carnivores) that feed on other organisms.
35. The Carbon Cycle Carbon is removed from the atmosphere by fixation during photosynthesis and returned by respiration, decomposition & burning fossil fuels
72. Gause’s experiment with Paramecium The two species of Paramecium used by Gause grew well by themselves but P. caudium was out competed by P. aurelia when the two were grown together
79. The Competitive Exclusion Principle Early in the twentieth century, two mathematical biologists, A.J.Lotka and V. Volterra developed a model of population growth to predict the outcome of competition Their models suggest that two species cannot compete for the same limiting resource for long. Even a minute reproductive advantage leads to the replacement of one species by the other
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83. Symbiotic Relationships - Parasitism - Commensalism - Mutualism SYMBIOSIS refers to relationships between organisms of DIFFERENT species that show an intimate association with each other Symbiotic relationships provide at least ONE of the participating species with a nutritional advantage 3 types of symbiosis have been recognised depending on the nature of the relationship:
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92. The gametocytes are ingested by the female mosquito in a bloodmeal from an infected human. The gametocytes fuse to produce a zygote.The zygote secrete a cyst containing sporozoites formed from meiotic divisions
93. Sporozites enters the liver cell and during the next two weeks the intracellular parasite reproduces by mitosis within a liver cell to form as many as 200,000 merozoites! On maturation, the merozoites rupture the liver cells and are are released into the blood where they invade human red blood cells
94. In the red blood cells, the parasite matures asexually to produce another 10-20 merozoites which in turn can rupture the red blood cell and invade more liver cells or red blood cells
108. The Costs, Benefits and Consequences of Interactions - Interaction between species - Interactions with the environment We have studied various types of biotic interaction that exist between species in an ecosystem. Now we are going to look at these interactions again, but this time we are going to concentrate on the COSTS , BENEFITS and CONSEQUENCES that these interactions have to the different species
122. Response curve Although organisms can tolerate a range of external environmental changes, they function most efficiently at certain optimum environmental conditions. An organism's responses to a changing environmental factor can be studied in the laboratory and a tolerance, or performance, curve can be produced
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134. (c) HUMAN IMPACT ON THE ENVIRONMENT Changes to Ecosystems (Changes in complexity, Effects of Intensive Food Production, Effects of Increased Energy Production, Pollution)
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141. In 1850, Connecticut was almost entirely open land cleared for farming or timber. Today, Connecticut has been mostly reforested through the process of secondary succession as farming has left the state since the 1800's This area has not been cleared in over fifty years. These trees represent the CLIMAX COMMUNITY for the rainfall, temperature and soil of this area This area has not been has not been mowed in about ten years. Shrubs and evergreen trees have moved in. These are the INTERMEDIATE species This area has been mowed within the last year. The plants are all annuals or herbaceous perennials. These are the PIONEER species
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146. CHANGES IN ECOSYSTEM COMPLEXITY Increase in complexity shown by: Number of species Population size Biological Productivity Habitat/Niche Variety Complexity of Food Webs Loss of complexity caused by: Monoculture Eutrophication Toxic Pollution Oxygen depletion AUTOGENIC SUCCESSION ALLOGENIC SUCCESSION DEGRADATIVE SUCCESSION Geophysical Forces (e.g. Climatic Extremes) Associated with Decomposition Primary Secondary Barren Land Colonisation by Pioneer Species e.g. moss, microbes Disturbance of Existing Community
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