Biogeochemical cycle human development of environment

Human development

1. BIOGEOCHEMICAL CYCLE NITROGEN CYCLE  Nitrogen is everywhere! In fact,     gas makes up about 78% of Earth's atmosphere by volume, far surpassing the     we often think of as "air" .   But having nitrogen around and being able to make use of it are two different things. Your body, and the bodies of other plants and animals, have no good way to convert    into a usable form. We animals—and our plant compatriots—just don't have the right enzymes to capture, or fix, atmospheric nitrogen . Still, your   and proteins contain quite a bit of nitrogen. Where does that nitrogen come from? In the natural world, it comes from bacteria! Bacteria play a key role in the nitrogen cycle. Nitrogen enters the living world by way of bacteria and other single-celled prokaryotes, which convert atmospheric nitrogen—  —into biologically usable forms in a process called nitrogen fixation. Some species of nitrogen-fixing bacteria are free-living in soil or water, while others are beneficial symbionts that live inside of plants.

2. Nitrogen-fixing microorganisms capture atmospheric nitrogen by converting it to ammonia— —which can be taken up by plants and used to make organic molecules. The nitrogen-containing molecules are passed to animals when the plants are eaten. They may be incorporated into the animal's body or broken down and excreted as waste, such as the urea found in urine.

3. Nitrogen doesn't remain forever in the bodies of living organisms. Instead, it's converted from organic nitrogen back into   gas by bacteria. This process often involves several steps in terrestrial—land—ecosystems. Nitrogenous compounds from dead organisms or wastes are converted into ammonia— —by bacteria, and the ammonia is converted into nitrites and nitrates. In the end, the nitrates are made into   gas by denitrifying prokaryotes. Nitrogen cycling in marine ecosystems: So far, we’ve focused on the natural nitrogen cycle as it occurs in terrestrial ecosystems. However, generally similar steps occur in the marine nitrogen cycle. There, the ammonification, nitrification, and denitrification processes are performed by marine bacteria and archaea.

4. Nitrogen cycling in marine ecosystems So far, we’ve focused on the natural nitrogen cycle as it occurs in terrestrial ecosystems. However, generally similar steps occur in the marine nitrogen cycle. There, the ammonification, nitrification, and denitrification processes are performed by marine bacteria and archaea.

5. Some nitrogen-containing compounds fall to the ocean floor as sediment. Over long periods of time, the sediments get compressed and form sedimentary rock. Eventually, geological uplift may move the sedimentary rock to land. In the past, scientists did not think that this nitrogen-rich sedimentary rock was an important nitrogen source for terrestrial ecosystems. However, a new study suggests that it may actually be quite important—the nitrogen is released gradually to plants as the rock wears away, or weathers.

6. Nitrogen as a limiting nutrient In natural ecosystems, many processes, such as primary production and decomposition, are limited by the available supply of nitrogen. In other words, nitrogen is often the  limiting nutrient , the nutrient that's in shortest supply and thus limits the growth of organisms or populations. How do we know if a nutrient is limiting? Often, this is tested as follows:  When a nutrient is limiting, adding more of it will increase growth—e.g., it will cause plants to grow taller than if nothing were added. If a non-limiting nutrient is instead added, it won't have an effect—e. g., plants will grow to the same height whether the nutrient is present or absent.

7. For example , if we added nitrogen to half the bean plants in a garden and found that they grew taller than untreated plants, that would suggest nitrogen was limiting. If, instead, we didn't see a difference in growth in our experiment, that would suggest that some other nutrient than nitrogen must be limiting. Nitrogen and phosphorus are the two most common limiting nutrients in both natural ecosystems and agriculture. That's why, if you look at a bag of fertilizer, you will see it contains a lot of nitrogen and phosphorus.

8. Human activity affects cycling of nitrogen. We humans may not be able to fix nitrogen biologically, but we certainly do industrially! About 450 million metric tons of fixed nitrogen are made each year using a chemical method called the Haber-Bosch process, in which    is reacted with hydrogen—   —at high temperatures.    Most of this fixed nitrogen goes to make fertilizers we use on our lawns, gardens, and agricultural fields. In general, human activity releases nitrogen into the environment by two main means: combustion of fossil fuels and use of nitrogen-containing fertilizers in agriculture. Both processes increase levels of nitrogen-containing compounds in the atmosphere. High levels of atmospheric nitrogen—other than   —are associated with harmful effects, like the production of acid rain—as nitric acid,    —and contributions to the greenhouse effect—as nitrous oxide,    .                                                                                                                  BY                                                                                         J.SHIVA                                                                        ROLL.NO: 23JJ1A1229                          THANK YOU..