gas, which contributes to smog. Another intermediary is the nitrous oxide (N2O) gas. This is considered a greenhouse gas, contributing to global warming. The goal is to make all N2 gas, which ultimately happens. It starts the process all over again. As you have probably surmised, man has contributed directly to greenhouse gases. The use of synthetic nitrogen fertilizers from chemically fixed nitrogen and the burning of fossil fuels has led to a lot of fixed nitrogen in the environment that hasn’t been there before. In addition, the groundwater has a lot of nitrogen in it. Drinking this groundwater with NO2 and NO3 in it (nitrite and nitrate, respectively) increases the cancer risk in humans. It has also led to the coastal fish-kill events from algae blooms in polluted ocean water. This has also led to an increase in NO gas, which is a component of smog and an increase in N2O gas, which is a greenhouse gas. This is where acid rain comes from, which leads to forest death and the decline in forests in parts of the US and Europe.
ECOSYSTEMS All of the different bacteria, animals, plants, and other organisms do not live in isolation. They live together in an ecosystem. An ecosystem, briefly, can be all the organisms living together in a small pond or tide pool; it can also be the entirety of the rainforest or grassland. An ecosystem is the combination of the organisms plus the physical environment. There are many populations or communities within an ecosystem that interact with the environment. The ecosystem is different from the community in that it involves the physical environment itself. A community is the living or “biotic” aspect of the totality of the ecosystem, making the ecosystem a combination of abiotic (environmental) and biotic factors. Ecosystems can be quite small or very large, depending on the circumstances. Ecosystems can be freshwater, marine-based, or terrestrial. The most common ecosystems are ocean ecosystems because oceans cover 75 percent of the earth’s surface. Freshwater ecosystems are the least common, comprising just 1.8 percent of the Earth’s surface. The rest are terrestrial.
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