An ecosystem is a collection of all the organisms that live in a particular place, together with their nonliving environment (Miller, 2003). A simple way it can defined is that it is a system containing a living community and a non living community (Kraus, 1999). All ecosystems have to include a source of energy, abiotic factors, biotic factors, a constant energy flow, material cycles, decomposers, and biodiversity. In a balanced ecosystem, a source of energy would would be sunlight. The amount of sunlight that reaches the Earth, which is less than 1 percent, is used by living organisms (Miller, 2003).
In some ecosystems, the main source of energy is not sunlight. Some organisms rely on energy stored in inorganic chemical compounds. Sources of energy play an enormous role in an ecosystem, since living systems cannot function without a constant source of energy. Abiotic and biotic factors also are vital in a balanced ecosystem. Abiotic factors matter in an ecosystem because organisms depend on them as much as the biotic factors in an ecosystem.
Some examples of abiotic factors are temperature, water, soil, gravel, and pH. Temperature effects an ecosystem because in an ecosystem where there is more heat than other places, it could result in different life forms that colder environments. Also, the biochemical processes of life are very dependent on temperature. Water is an important abiotic factor in an ecosystem because many life activities take place in the medium of water. In addition, without water, many life processes that occur in organisms to maintain homeostasis would not occur.
Soil is an important abiotic factor to an ecosystem because soil is the basic medium for almost all land ecosystems. Both plants and animals use it to grow and thrive. In addition, many inorganic elements that organisms need are found in soil. Gravel is an abiotic factor because it is a mixture of sand, clay and small pieces of rock, and it is used as a base, like soil. It is used to filter out substances in fish tanks and the sort (Sitko, 2003). The amount of pH found in an ecosystem is also considered an abiotic because if an ecosystem has a very high pH, than the acidity will affect the organisms in the environment somehow because a high pH can be poisonous to organisms.
Biotic factors in an ecosystem are important as well because it includes all the living organisms in an environment. Producers and consumers are examples of biotic factors. This leads to the topic of energy flow through feeding relationships. Producers, or autotrophs, use energy from the environment to turn inorganic compounds into complex organic molecules. These organic materials then produce living tissue. Basically, producers, which can obtain energy from sunlight or from chemical energy, are essential in the process of energy flow. Next on the energy flow process comes organisms called heterotrophs. Heterotrophs, also known as consumers, rely on other organisms for their energy and food supply. There are many different types of heterotrophs. Some are herbivores, which obtain energy by eating only plants. Some are carnivores, which only eat other animals. Some are omnivores, which eat both plants and animals. Finally, some are detritivores which feed on dead matter. An important part of heterotrophs are decomposers which break down organic matter. Energy flows through an ecosystem in one direction. Energy basically goes from the sun or inorganic compounds to autotrophs to different heterotrophs. Some ways to describe a feeding relationship is a food chain and a food web. A food chain is a series of steps in an ecosystem in which organisms transfer energy by eating and being eaten. A food web is a network of complex interactions formed by the feeding relationships among the various organisms in an ecosystem (Miller, 2003). The flow of energy in a food web or in a food chain is different in biogeochemical cycles since matter is recycled within and between ecosystems. Since every living thing need nutrients to carry out essential life functions, nutrients are passed between organisms and the environment through biogeochemicals.
Three nutrient cycles play important roles in the biosphere, the carbon cycle, the nitrogen cycle, and the oxygen cycle. Recycling nutrients are extremely important because it keeps ecosystems functioning and it helps from reaching concentrations that would be toxic.
The Carbon cycle is extremely important to all living organisms. There are 4 processes associated with carbon, the biological processes, the geochemical processes, the mixed biogeochemical processes, and human activity. The Oxygen cycle is extremely important because without it organisms couldn't breathe. Oxygen is created when plants use the process of photosynthesis. Oxygen is let out as waste and is used by all living things. Plants also use oxygen during cellular respiration. The Nitrogen cycle is also extremely important since Nitrogen is needed to make amino acids to build proteins. Nitrogen gas makes up 78 percent of the atmosphere, and it can be made through the processes of nitrogen fixation and denitrification. In addition, in an ecosystem there has to be biodiversity. Since biodiversity is the sum total of the genetically based variety of all organisms in the biosphere, ecosystem biodiversity is the inclusion of the variety of habitats, communities, and ecological processes in the living world (Miller, 2003). However, an ecosystem has to have a carrying capacity. Carrying capacity is the largest number of individuals of a population that a given environment can support. An ecosystem also has to have ecological succession which is the gradual change in living communities that follows a disturbance. There are 2 types of succession, primary and secondary. Primary takes place on land that is almost lifeless and secondary occurs in an existing community that has been partially destroyed. The problem this experiment was to construct a soda bottle miniature ecosystem. The hypothesis was that a self sustaining miniature ecosystem can be created in a soda bottle with all the biotic and abiotic features needed to survive.
In this experiment the materials used were a 2 liter bottle with cap, a pencil, one water snail, 2 guppies, gravel, paper towels, forceps, a funnel, a popsicle stick, newspaper, Elodea, a gallon of aged water, shrimp eggs, pH paper, rulers, a triple beam balance, and a thermometer. First, the bottle was rinsed with aged water in order to remove any foreign substances from it. Next, about 500 grams of gravel was washed with aged water. After that, the washed gravel wash was poured into the soda bottle until it reached up to an inch inside the bottle. The amount of gravel put in the bottle should measure about 390 grams. Next, aged water was poured into the bottle until it filled up 34 of the bottle. After that, the water snail was picked up using the forceps and dropped into the bottle. Next, the guppies were placed into the bottle through a funnel. Then, 3 Elodea plants were inserted into the bottle. After that, a popsicle stick was used to pick up shrimp eggs from a container and insert them into the bottle. Next, the temperature of the water was measured and recorded. After the temperature was measured and recorded, the pH of the water was measured and recorded. Finally, the bottle was closed with the cap to prevent any pathogens or microorganisms from entering the ecosystem. The bottle was kept in room temperature with a sufficient amount of sunlight so that the Elodea could survive and perform the process of photosynthesis. The pH and temperature were recorded for 5 days total. As the temperature and pH were recorded, 3 observations were made and recorded each day about the current status of the bottle.
In the mini ecosystem, for the first few days, the guppies were thriving and the Elodea leaves were bright and green. According to Tables 2 and 3, the observations show that the guppies were alive and well. It even appears that they had grew since the color of their bodies had gotten darker, according to Table 2. After a day however, all the fish had died, and the leaves appeared to have been nibbled on. The snail was also dead and was floating on top of the water. After the fish had died, the ecosystem kept on deteriorating. On Day 4, which is recorded on Table 5, it was observed that the snail had continued to float on top of the water, but it appeared to be torn up. The Elodea leaves had also turned brown and the bodies of the guppies were nowhere to be seen. The next day, Table 6, the torn up snail which had been floating on the top of the water had now sunk to the bottom, and it laid on top of the gravel. In addition, several brown Elodea leaves had fallen off from the Elodea plant stalks and had sunk to the bottom as well. In the end, nothing had survived in this mini ecosystem that was created. This may have happened since according to Table 1, the temperature of the water had been decreasing and the pH level had been increasing. If the pH, or the acidity, in the water increased that may have caused the guppies to react to the change.
All in all, the experiment was unsuccessful. Even though the experiment included all the components of a balanced ecosystem, something went wrong that caused the mini ecosystem to deteriorate and fail. The question we may now ask is, what went wrong? The mini ecosystem had a source of energy, abiotic and biotic factors, a constant energy flow, material cycles, and biodiversity. The source of energy was sunlight that entered the room. The abiotic factors were temperature, pH, gravel, and water. The biotic factors were the guppies, the Elodea, the shrimp eggs, and the snail. The constant energy flow was that the guppies either ate the shrimp eggs, or nibbled on the Elodea, and that the snail consumed algae or it ate wastes of the guppies. The material cycles that have taken places are the Oxygen cycle and the Carbon cycle.
On the first day, the guppies were alive and well, and the snail was moving around in the water, so it was presumably healthy. The Elodea was also very green, so the conclusion that can be drawn is that the ecosystem was balanced and functioning because it was receiving a sufficient source of energy. The temperature and pH was unchanging and the amount of gravel and water stayed the same. The biotic factors were alive and healthy. The energy flow from producers to consumers must have been functioning correctly. The material cycles were occurring, since the fish were breathing. In addition, in our mini ecosystem, we had enough biodiversity, but we had not yet reached the carrying capacity of the given environment. On the second day, the Elodea leaves had started discoloring since it started turning brown. But, the fish were still alive although they had also appeared to have gotten darker. The snail had also moved from its original position. The source of energy still remained the same. However, the abiotic factors seemed to have changed. The temperature of the water had decreased, while the pH of the water had increased. The gravel amount, and the amount of water had still remained the same though. The biotic factors had gone through little change, although there was no sign of the shrimp eggs. The energy flow remained the same. The material cycles also had no change. Basically, the second day was similar to the first day showing that the ecosystem was functioning. On the third day, both the fish and the snail were dead. The Elodea leaves appeared to have been nibbled at. While the source of energy remained the same, the abiotic factors had changed again. The temperature and the pH both had changed, the temperature having decreased and the pH having increased. The water and gravel levels remained the same. Nearly all the biotic factors were dead, since only the Elodea remained alive. The energy flow had changed because now, only the plant received
energy from the sun, but the plant didn't pass it on to any other organism. The material cycles had also changed because the plant would still be producing oxygen, but it couldn't absorb oxygen since there were no organisms that was actually producing oxygen in the mini ecosystem. After this, the mini ecosystem continued to deteriorate. At the end of Day 5, everything was dead. The guppies may have died because of the loss of nutrients that were provided to them. The reason why the snail died is unknown, but the Elodea died because of the loss of material cycles.
After the fish all died, ecological succession did occur in the ecosystem because the death of all the organisms led to the decomposition of the ecosystem. Since succession is the replacement of one biotic community by another, (Kraus, 1999), the current biotic community with the dead fish, the dead snail, and the dead elodea were being replaced by a biotic community with bacteria and decomposers. The carrying capacity was not achieved because carrying capacity is the largest number of individuals of a population that a given environment can support. (Miller, 2003) Since everything died in the miniature ecosystem, there was no way that the carrying capacity could have been reached. The toxicity of the ecosystem could have been a factor to why everything had died in the ecosystem. Since the final measurement of the pH was 7, we don't know whether a guppy or a snail could havesurvived in that pH.
Some improvements that could have made to the original design of the experiment is that for a miniature ecosystem to sustain itself without any intrusion from outside forces is that the organisms should be given a sustainable amount of nutrition so that it can't run out, so the organisms will not die from starvation. In the original experiment, the organisms may have died from loss of nutrition. So one improvement that we can modify is that we must add a more sustainable supply of food, so that it will not run out. The broader significance of theexperiment is that biotic features depend heavily on abiotic features in order to survive, while abiotic features also depend on biotic components. Also, this shows how biotic features cannot survive without the necessary components of an ecosystem such as a food supply, temperature, oxygen, space, and acidity. The next steps that could be taken from this point is that if this experiment can be done correctly, and a functional ecosystem can be maintained without any disturbances from an outside force, then the same procedure could be applied to ecosystems that are experiencing extreme distress from the loss of the essential factors of an ecosystem.