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Principles of Ecology Dr. James Looney AP Biology West Windsor-Plainsboro HS North Abiotic factors determine the make-up and characteristics of ecosystems • What are abiotic factors? • What are the most important abiotic factors that determine whether a region is a desert, a grassland, or other type of biome? Abiotic factors • Abiotic factors are physical, non-living factors. • Abiotic factors include – Temperature (both average and seasonal patterns are important) – Precipitation (average, seasonal patterns, and forms of precipitation) – Amount of Sunlight – Wind – Soil conditions (nutrients, pH) Identify some abiotic factors in this Delaware Shore ecosystem Abiotic factors • What are the most important physical parameters in an environment that effect abiotic factors? Abiotic factors • What are the most important physical parameters in an environment that effect abiotic factors? • Location! Location! Location! – In particular, latitude and altitude are the two most important physical parameters. • Explain WHY. How does latitude effect the amount of sunlight that strikes a given location each year? How does latitude effect seasonal weather patterns? 2. Nutrients cycle in ecosystems • One example of nutrient cycling is seen in the nitrogen cycle. • What types of organisms play important roles in the nitrogen cycle? • What roles do bacteria play? • Why do organisms need nitrogen? All organisms require nitrogen for the synthesis of amino acids (and proteins) and nucleic acids. Figure 2.31 The Nitrogen Cycle Courtesy EPA Source: http://www.epa.gov/maia/html/nitrogen.html Animals excrete nitrogen in nitrogenous wastes: mammals excrete urea in urine, fish excrete ammonia, and birds and insects excrete uric acid. See Fig. 44.8 in Campbell Biology. Disturbances • Disturbances in the nitrogen and phosphorous cycle may lead to – Depletion of nutrients in an ecosystem Disturbances • Disturbances may also lead to cultural eutrophication where an excess of nutrients accumulate in an ecosystem. • Of particular importance are ocean, stream, and lake dead zones. • Where are these dead zones located, and what causes dead zones? Cultural eutrophication • A single nutrient may be a limiting factor. If that nutrient is added, for example, to a lake, stream, or other body of water, algae and plant blooms may occur. • While this may happen with any nutrient, Phosphorous is often limiting in many aquatic systems. Carbon also cycles, typically on a broader scale. Identify where and how carbon fixation occurs. The Carbon Cycle How much carbon is being added to the atmosphere on a yearly basis? Where are the major sinks or reservoirs of carbon in the world? The Carbon Cycle: An increase in carbon dioxide in the atmosphere has been measured over the last 50 years. Levels of carbon dioxide in the atmosphere have increased since measurements began in 1958. This graph is known as the Keeling Curve in honor of Charles Keeling (1928-2005) who measured carbon dioxide levels at the Mauna Loa Observatory in Hawaii beginning in 1958. 3. Energy, unlike nutrients, does not cycle but is lost to the environment as you travel up the food chain. • How is energy lost to the environment? For example, what activities does a mouse do where energy will be lost to the environment? 4. All communities of organisms in an ecosystem are dependent on the producers • The producers (the autotrophs) capture energy from a physical source and convert it to chemical energy. • What are the producers in – Aquatic systems like the open ocean? – Grasslands? – The tundra? – Deep Sea thermal vents? Producers: Photosynthetic • Most producers are photosynthetic and capture the energy from sunlight. A marsh near Cape Elizabeth, Maine where grasses are abundant. Producers: Chemosynthetic In some ecosystems, like the deep sea thermal vent shown to the left, producers (chemosynthetic bacteria) capture energy from inorganic compounds like hydrogen sulfide and convert that energy into chemical energy. 5. Productivity measures the energy captured by autotrophs • Gross primary productivity measures the energy transformed by autotrophs into chemical energy(Joules)/unit area/year. Since some of this energy is used by producers for their own energy requirements for metabolism, growth, etc. and is not available to the next highest trophic level . . . • Net primary productivity is also measured and more accurately reflects the contribution producers make to the food chain. • Productivity can also be measured in dry biomass produced (g/unit area/year) 6. All organisms interact with the environment and require specific adaptations for their survival. • Can you give specific examples of organisms and their adaptations from each type of ecosystem found in the world? Adaptations: antifreeze proteins Many fish in the Antarctic, like the one to the right (Macropteris maculatus), produce antifreeze proteins. These antifreeze proteins inhibit ice crystal growth in their bodies and allow the fish to live in subzero waters. 7. All organisms interact with other organisms. • Competition may occur between organisms of two different species (interspecific competition) or between organisms of the same species (intraspecific competition) The Competitive Exclusion Principle Conducting laboratory experiments with two species of Paramecium, the Russian ecologist G. F. Gause concluded that two species of organisms competing for the same limiting resources can not coexist together. When grown separately, each species thrives. When grown together, only one species (Paramecium aurelia) survives and the other dies. See Campbell Biology page 1160 Competition • Competition (a -/- interaction) may also occur between organisms of the same species. In the WW-P HS North ecology study site, succession is occurring. In the foreground, several small oak trees are growing close together, competing for space and limited resources. Come back in 10 or 20 years and see which oak tree(s) wins the race to the top! Types of interactions: Predation • +/- interaction where the predator kills and eats the prey. Types of Interactions: Herbivory • +/- interaction where the herbivore eats part of a plant or alga but doesn’t kill it. Plant defenses against predation Tear a portion of a leaf from a milkweed plant(shown in the middle of the photo) and a milky substance will flow out. Most herbivores find the substance noxious and avoid eating the plant. An exception to the above is the monarch butterfly which lays its eggs on milkweed The caterpillar of the monarch is able to eat the milkweed and in fact will incorporate the noxious substance from the milkweed in its tissue as an adult. A variety of other plants produce substances which act as a deterrent to herbivores. Types of interactions: Mutualism • +/+ interaction where both organisms benefit • Mutualism is a type of symbiosis, a close interaction between two organisms. Mutualism: Nitrogen-fixing bacteria in the root nodules of legumes A soybean plant (above; a type of legume) with root nodules. The root nodules are visible above and to the right of the pencil tip. Root nodules contain nitrogen-fixing bacteria. How are the bacteria beneficial to the plant? How is the plant beneficial to the bacteria? Mutualism • How many other forms of mutualism can you identify? Mutualism • Did you think of . . . – Pollinators and flowering plants? – Bacteria in the digestive tracts of humans? – Bacteria in the digestive tracts of termites, cows, and other types of animals? – “Fungus roots” (mycorrhizae), mutualistic fungusplant root associations – Alga and coral?