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Transcript
Ecology Part 3 A FOOD CHAIN is the sequence of organisms through which energy and materials may move in a community. In Communities, each level of the food chain is called a Trophic Level The usual order of this transfer is from Producers to Consumers to Decomposers…….. These are 2 food chains for two different environments, terrestrial and marine. In most communities the food chains are completely intertwined to form a FOOD WEB. The direction of the arrow indicates the upward movement of energy and material. The successive levels of food and energy in the food chains are called trophic levels. The producers constitute the first trophic level, and the primary consumers, the second and so on. Since many species eat a varied diet, trophic levels are not hardand-fast categories. At each trophic level there is a loss of energy from the system. Only a small percentage of the energy at one trophic level is available for the next. (usually about 10%) Lost energy and materials is usually caused by one or more of the following: 1. The inability to consume and process all that is eaten 2. Loss of energy due to dissipation of heat energy. 3. Energy is used for growth and reproduction. The PYRAMID of PRODUCTIVITY is the basis that a pyramid of biomass exists. In general the decrease of energy at each successive trophic level means that less biomass can be supported at each level. Hence the total mass of carnivores in a given community is almost always less than the total mass of herbivores. The pyramid of productivity and the pyramid of biomass support the pyramid of numbers. This is because in general, carnivores are larger than the herbivorous prey . Since total biomass tends to decline at successive trophic levels, it follows the number of individuals must decline at each level (except decomposer which outnumber all other groups combined). GROSS PRIMARY PRODUCTIVITY is the ability of producers to “fix” or convert carbon dioxide into organic material. NET PRIMARY PRODUCTIVITY is the amount of organic material that is produced beyond what is needed by the living organisms in an ecosystem. A DOMINANT SPECIES in an ecosystem are species which are present in the greatest numbers or greatest biomass. A KEYSTONE SPECIES is an important species that can exert an effect on regulating others in a community. For ex. Phytoplankton is a Keystone species in the marine environment Sea otters are considered to be a keystone predator species. Sea otters prey on sea urchins. Sea urchins eat kelp. Where sea otters are plentiful, sea urchins are rare and kelp beds are plentiful. Where sea otters are population is low, sea urchins are plentiful and kelp beds are almost absent. Whales in the last 20 years have been preying on sea otters, this has increased the sea urchin population and decreased the kelp beds off the coast of western Alaska. SPECIES DIVERSITY refers to the different number of species in a given area.. In general, the greater the species diversity of an ecosystem, the more stable the ecosystem. •An ecosystem with fewer species may be more susceptible to damage from some sort of disturbance, however it may recover quickly. •An ecosystem with more species may be more stable and less resistant to change from a disturbance, however it may be more difficult for the ecosystem to recover when a serious disturbance does occur. While both of these ecosystems have the same number of species of trees, the first community is more stable because of the relative number of individual trees is almost equal unlike the second community where one species dominates. SUCCESSION: is the process of change in which one community of organisms replaces another. This happens after some sort of change- volcano, fire, tornado, etc has disturbed the environment. As each community is established, the environment is modified and change making it possible for another community to become established. Primary succession: begins with bare rock or sand and involves first the building of soil. Once organisms colonize an area, they change it so that other organisms may follow. Examples include what happens after a volcano erupts or glacier retreats. Primary succession: begins with bare rock or sand and involves first the building of soil. Once organisms colonize an area, they change it so that other organisms may follow. e.g. The first organisms to colonize the area may be mosses and lichens. These plants may produce acids as a waste produce to break down rocks in the formation of soil. Simple plant species will begin the next step Succession over time from simple to complex organisms Another example of succession is that found in a pond. First the pond is barren but then the aquatic plants die and sediments begin to fill in and begins to be ringed by vegetation. The beginnings of pond succession. It is barren with little vegetation. 50 yrs. the pond is bordered by mature cottonwood trees. 2 yrs. the pond is ringed by vegetation including cotton wood saplings. 150-200 yrs. the pond has become a meadow, the pond is ringed by vegetation. Secondary succession- Soil is present and occurs at a much more rapid rate. Can be the result of fire, tornados, floods and other like events. Examples also include abandoned crop lands, unused rail roads etc. The Pioneer Species are the first types of life to grow in a newly created area. Ecological succession may lead to a stable community of plants and animals called the Climax Community. A Biome is an environment that has a characteristic climax community. The earth has two main types of biomes, land biomes and aquatic biomes. Most land biomes are named for their climax community or dominant type of plant life. The major types of biomes are the arctic, tundra, taiga, temperate deciduous forest, grassland, tropical rain forest, and desert. Arctic Biome Where found- Extreme North and South Poles, Extreme elevation as in tops of Mountains Ranges Plant Life- None Animal Life- Marine organisms including penguins, seals, Killer Whales, Phytoplankton, Zooplankton, Krill Extreme cold, Long winters, little direct sunlight TUNDRA Where Found: northern North America, Europe, Asia Plants: mosses, lichens, grasses, a few stunted trees Animals: caribou, reindeer, wolves Other Characteristics: permafrost – creates freezing and thawing cycle TAIGA Where Found: most of Canada and Asia Plants: pine trees Animals: bears, wolves, moose, elk, voles, wolverines, Characteristics: long and cold winter, summers completely thaws the soil. TEMPERATE DECIDUOUS FOREST Where Found: southern Canada, eastern U.S., Europe, and Japan Plants: trees that lose their leaves (oak, maple, birch) Animals: huge variety, including fox, deer, moose, etc. Characteristics: lands cleared by hunting and farming GRASSLANDS Where Found: interior of many continents Plants: grasses and small leafy plants Animals: grazers and browsers Characteristics: Large variation in temperature and seasonal changes. Grazing and prairie fires halts succession. TROPICAL RAIN FORESTS Where Found: South America, S.E. Asia, Central Africa, Central America Plants: rich vegetation in canopy and undergrowth Animals: colorful insects, lizards, amphibians, reptiles, small mammals o Characteristics: 200 – 400 cm rain, constant (25 C) DESERTS Where Found: northern Africa, southern Asia, central Australia Plants: cactus and other non-leafy plants Animals: lizards, small rodents Other Characteristics: very little rainfall, although some deserts have seasonal rain Aquatic Biomes---- May be either, Fresh Water, Salt Water or Estuary. Fresh Water Biomes have three levels, each depends on the amount of Sunlight it receives and the depth of the Water. 1. Littoral Zone- Shallow water near the shore. Edges of lakes and big ponds, edges of Rivers and Streams and Swamps. Plenty of Aquatic plants, amphibians and small fish 2. Limnetic Zone- Area close to the surface but away from shore. Limited floating plants, algae, surface fish 3. Profundal Zone- Area is deep water below the limits of sunlight. Life limited to bottom feeders, bacteria, worms. Not all freshwater biomes have a Profundal zone. Salt Water (Marine) Biomes- There are also three levels of Zones in Marine Biomes. 1. Shoreline (Coastal) Zone- Beach areas – abundant grasses and palm trees in tropical areas. Crabs, Sea Birds, Oysters etc. 2. Surface Zone- Open Ocean where sunlight penetrates to about 300 meters. Fish, dolphin and floating seaweeds. Plankton is abundant! 3. Abyssal Zone- Zone below 300 Meters. Total absence of Light. Water Pressure is greater with depth. Few organisms can live here as there is little food available. Large invertebrates such as tube worms, squid and other exotic species can be found here. Estuary----Bay like areas where Salt water and Fresh water mix- The three largest Estuaries in the US are the Chesapeake Bay, San Francisco Bay and Long Island Sound Estuaries are in tidal zones and may also include Marshlands near the coast. Highly diverse in life, many bay plants, invertebrates, fish, mollusks, birds and mammals. Maybe the most complex of all food webs! Biogeochemical Cycles In Nature Nutrients are recycled into the ecosystem unlike energy. The major nutrient cycles are water, carbon, nitrogen and phosphorus. In the Carbon Cycle, carbon is recycled mainly through the process of photosynthesis, cellular respiration and burning of fossil fuels. Carbon dioxide (CO2) and carbon monoxide emissions have been increasing in the atmosphere. It allows light energy in, but traps the reflected heat energy in atmosphere so that it does not go back into space. Potential Global Warming could have disastrous effects! •Nitrogen used for proteins and nucleic acids. The air is over 75% N2, but this nitrogen can not be used because of its triple bond. •Nitrogen Fixation occurs in Legume Plants and Lightning •Animals can only get their nitrogen from eating plants or other animals. •Nitrogen also gets into the soil when man uses fertilizers made from factories. •Bacterial Nitrification is the process of putting N2 back into the ecosystem. Another way to get nitrogen into the ecosystem is through decaying organisms and wastes. Water Cycle- Water passes from the atmosphere to the ground as precipitationRain, Snow, Sleet, Hail, and Dew occur when the atmosphere cannot hold the moisture. •Rainfall may soak into the soil, be taken up by plants or animals or may run-off into creeks, streams or other bodies of water. A very high % of water is in groundwater. •Water returns to the atmosphere by Evaporation, Transpiration and Respiration. The phosphate cycle is the one nutrient that does not have an atmospheric component. It cycles through the soil and water. The main source of phosphorous is the weathering of rocks.