Ecosystem Ecology I
3. Draw a labeled diagram of energy and nutrient movement within an ecosystem and use it to explain the relationships among trophic levels, how energy and nutrients move between trophic levels, and what processes are occurring.
Ecologist group species into trophic levels based on their main source of nutrition and energy. The trophic level that ultimately supports all others consist of autotrophs are called the primary producers. Most autotrophs are photosynthetic organisms that use light energy to synthesize sugars and other organic compound. o Ex: plants, algae and photosynthetic prokaryotes. Organism in trophic levels above the primary produces are heterotrophs, which depend directly or indirectly on the outputs of primary producers for their source of energy. Herbivores eat plants and other primary produces are primary consumers. Carnivores that eat herbivores are secondary consumers. Carnivores that eat other carnivores are tertiary consumers. Another group of heterotrophs are the detritivores or decomposers, they get energy from detritus. Detritus: nonliving organic material, such as the remains or dead organisms, feces, fallen leaves, and wood. They are then consumed by tertiary consumers. These organism secrete enzymes that digest organic material, they then break them down. Linking the consumer and primary produces in an ecosystem. They also convert organic materal from all trophic levels to inorganic compounds usable by primary producers, closing the loop of an ecosystem's chemical cycle. If these decomposer stopped, the detritus would pile up and the supply of ingredient needed to synthesize organic material matter are exhausted
Define what a limiting nutrient is, giving examples and comparing the limiting nutrients in different ecosystems. Relate this to the phenomenon of eutrophication.
More than light, nutrients limit primary production in most oceans and lakes. A limiting nutrient: the element that must be added for production to increase. The nutrient most often limiting marine production is either nitrogen or phosphorous. Concentrations of these nutrients are typically low in the photic zone because they are rapidly taken up by phytoplankton and because detritus tends to sink. Studies have shown that nitrogen was limiting phyloplankton growth off the south shore of long island new York. One explanation of this work is in preventing alagal blooms created by excess nitrogen runoff that fertilizes phyoloplankton. The macronutrients nitrogen and phosphorous are not the only limiting factors that limit aquatic production. Several large areas of the ocean have low phytoplankton densities despite high levels nitrogen concentration. The Sargasso Sea a region in the Atlantic Ocean, has some of the clearest water because of the lack of plankton. Nutrient enrichment shows that this is because of the availability of iron that limit production. Area of upwelling, nutrient rich water that circulate to the ocean surface have high primary production. Because upwelling stimulate growth of phytoplankton that from the base of marine food webs, upwelling area typically host highly productive diverse ecosystems. In freshwater, nutrient limitation is common. Scientist showed that the sewage and fertilizer runoff from farms and lawns adds considerably nutrients to lakes, promoting the growth of primary producers. When the primary producers die, detritivore decompose them depleting the water or much or all of its oxygen which is eutrophication. to control this, scientist need which nutrient is responsible. Whole lake experiment shows that phosphorus availability limit cyanobacterial growth.
1. Distinguish among populations, communities, and ecosystems
Population are a group of one species. Communities are a group of populations. Ecosystems: the sum of all the organisms living in a given area and the abiotic factors with which they interact. An ecosystem can encompass a vast area, such as a lake, forest, or island or a microcosm, such as the space under a fallen log or a desert spring. As with populations and communities, the boundaries of ecosystems are not always discrete.
4. Explain which ecosystems are most productive and what accounts for their high productivity.
Primary production: the amount of light energy converted chemical energy in the form of organic compounds by autotrophs during a given time period. These photosynthetic products are the starting point for most studies of ecosystem metabolism and energy flow. The intensity of the solar energy striking Earth varies with latitude, with the tropic receiving the greatest input. Most solar radiation is absorbed, scattered, or reflected by clouds and dust in the atmosphere. The amount of radiation that ultimately reached Earth's surface limits the possible photosynthetic output of ecosystems. Only a small fraction of the sunlight that reaches the earth's surface is actually used in photosynthesis. Tropical Rain Forest are the most productive terrestrial ecosystems and contribute a large portion of the planet's Net Primary Production. Net primary production is equal to gross primary production minus the energy used by primary producers for their autotrophic respiration. It's the energy per unit of time or the bio mass per unit of time. This represents the storage of chemical energy that will be available to consumers in the ecosystem. Also, the NNP is the amount of new biomass added in a given time. NNP is not the total biomass of photosynthetic autotrophs present. A forest can have a large standing crop, its NPP may actually be less than that of some grasslands, grassland don't not accumulate as much biomass as forest because animals consume the plants rapidly and because grasses and herbs decompose more quickly than the trees do. Net Ecosystem Production (NEP) is the measure of the total biomass accumulation during that time. It is defined as gross primary production minus the total respiration of all organisms in the system not just primary producers. It can be useful because it value determines whether an ecosystem is gaining or losing carbon over time. Ecologist do this by measuring the flux of CO2 of O2 entering or leaving the ecosystem. If more CO2 enters than leaves, the system is storing carbon. Also if a system is giving off more O2 it is storing Carbon.
2. Distinguish energy flow from nutrient cycling, and describe why they are different.
Two key ecosystems processes cannot be fully described by population or community phenomena: energy flow and chemical cycling. Energy enters most ecosystems as sunlight. It is converted to chemical energy by autotrophs, passed to heterotroph in the organic compounds of food and dissipated as heat. Chemical elements such as carbon and nitrogen are cycled along abiotic and biotic components of the ecosystem. Photosynthetic and chemosyntatic organisms take up these elements in inorganic form from the air, soil, and water and incorporate them into their biomass which is consumed by animals. Both energy and matter are transformed in ecosystems through photosynthesis and feeding relationships. But unlike matter, energy cannot be recycled. An ecosystem must be powered by a continuous influx of energy from an external source, like the sun. Energy flows through the ecosystem, whereas matter cycles within and thru them. Conservation of Energy Some information is above, but... The first law of thermodynamic states that energy cannot be created or destroyed but only transformed or transferred. Plants and other photosynthetic organisms convert solar energy to chemical energy, but the total amount energy will not change. The second law of thermodynamics that every exchange of energy increases the entropy of the universe, they energy conversion are inefficient. Since the energy flowing through ecosystems is ultimately dissipated into space as heat, most ecosystems would vanish if the sun were not continuously providing energy to Earth. Conservation of Mass Matter also cannot be created or destroyed. Chemical elements are continually recycled within ecosystems. a carbon atom in CO2 is released from soil by a decomposer, taken up by a grass through photosynthesis, consumed by a grazing animal, and then returned to the soil in the animal's waste. Most elements are not gained or lost on a global scale, but Most element are not gained or lost from a particular ecosystem. In a forest, most mineral nutrients, the essential elements from plants obtain from soil - typically enter as dust or as solute dissolved in rainwater or leached from rocks in the ground. For losses, some elements return to the atmosphere as gases, and others are carried out of the ecosystem by moving water or by wind.
