Biogeochemistry is the science that studies the chemical processes that take place in the atmosphere and hydrosphere, and more specifically, the flux of elements between them.
Biogeochemical cycles represent the movement of chemical elements between living beings and the planet's atmosphere, lithosphere and hydrosphere.
A fundamental feature of biogeochemical cycles is the fact that biotic and abiotic components are closely related.
Chemical elements are removed from the environment, used by organisms and returned to nature. Life is continually being recreated from the same atoms.
When an organism dies, its organic matter is degraded by beings. decomposers, represented by fungi and bacteria. Thus, the atoms that made up this organism return to the environment and can be incorporated again by other living beings to produce their organic substances.
Without this recycling, the atoms of some chemical elements fundamental to life could disappear.
For the biogeochemical cycle to occur, the existence of a reservoir of the chemical element is necessary. This reservoir could be the earth's crust or the atmosphere. Furthermore, living beings that assist in the movement of chemical elements are needed.
Classification of Biogeochemical Cycles
Biogeochemical cycles can be classified into two basic types, depending on the nature of their abiotic reservoir:
gas cycle: Possess the atmosphere as a reservoir. Example: Nitrogen Cycle and Oxygen Cycle.
Sedimentary Cycle: They have the earth's crust as a reservoir. Example: Phosphorus Cycle and Water Cycle.
The elements necessary for life participate in biogeochemical cycles. They are: water, carbon, oxygen, nitrogen and phosphorus.
water cycle
Water is fundamental to life and can be found in nature in three physical states: solid, liquid and gas. Most are found in liquid form.
The water cycle is basically represented by changes in its physical state, through the evaporation and perspiration.
In short, the water cycle occurs as follows:
- Water present in lakes, rivers and oceans evaporates. And plants release some of the water they absorb through transpiration.
- Water vapor finds the highest layers of the atmosphere. Upon cooling, this vapor condenses and forms clouds, which precipitate as rain.
- Thus, liquid water reaches the earth's surface again.
- The water then infiltrates the soil and is absorbed by the plants. Animals can ingest directly or through food.
Learn more about water cycle.
carbon cycle
O carbon it is the element that makes up organic molecules.
THE photosynthesis and the breathing they are processes that govern the carbon cycle.
The carbon cycle consists of the fixation of this element by autotrophic beings, through photosynthesis or chemosynthesis.
Autotrophic beings fix carbon in the form of organic compounds. Thus, they are available to producers and, consequently, to consumers and decomposers, through the food chain.
the CO2 returns to the environment through respiration, decomposition or burning of fossil fuels.
Learn more about carbon cycle.
Oxygen Cycle
The oxygen cycle consists of the movement of this element between its three main reservoirs: the atmosphere, the biosphere and the lithosphere. O oxygen it is released and consumed by living beings in different chemical forms. These factors make the carbon cycle more complex.
Photosynthesis is primarily responsible for the production of oxygen.
The atmosphere is the main reservoir of oxygen for living beings, where it can be found in the form of O.2 and CO2.
O O2 It is used in aerobic respiration of plants and animals, in which the combination of oxygen and hydrogen atoms form water molecules.
the CO2 is used in the photosynthesis process and its oxygen atoms become part of the organic matter of plants.
Through cellular respiration and decomposition of organic matter, oxygen is returned to the atmosphere, forming part of water molecules and carbon dioxide.
Learn more about Oxygen Cycle.
Nitrogen Cycle
Nitrogen is the most abundant chemical element in the Earth's atmosphere. Found in the form of N2, represents approximately 78% of the atmospheric air volume.
However, the vast majority of living beings cannot assimilate atmospheric nitrogen. For this, they need nitrogen-fixing bacteria.
There are four types of bacteria that participate in the nitrogen cycle:
- Fixing Bacteria: absorb atmospheric nitrogen and transform it into ammonia.
- Nitrifying Bacteria: chemosynthetic bacteria that oxidize ammonia and transform it into nitrite and then nitrate, a form assimilable by plants. Thus, through feeding the animals can obtain nitrogen.
- Decomposing Bacteria: bacteria that act when organic matter decomposes and release ammonia into the environment.
- Denitrifying Bacteria: bacteria that anaerobic degrade nitrogen compounds, such as nitrates and ammonia, and release nitrogen gas into the atmosphere.
Learn more about Nitrogen Cycle.
Phosphorus Cycle
Phosphorus is the genetic material that makes up RNA and DNA molecules. It can also be found in bones and teeth.
In nature it is found only in rocks, in its solid form. When rocks degrade, phosphorus atoms become available in soil and water.
Plants can obtain phosphorus when they absorb it dissolved in water and soil.
Animals obtain phosphorus through water and food.
Phosphorus is returned to the environment by decomposing organisms as a result of the degradation of organic matter in plants and animals. From there, it can be recycled among plants or taken by rainwater to lakes and seas and incorporated into the rocks.
Exercises - Test your knowledge
(PUC-RS-2001) - The nations of the world have discussed the possibility of rich and polluting countries paying taxes to developing countries that maintain and/or plant forests. This would be a way to mitigate the contribution of polluting countries to the "greenhouse effect" (the phenomenon responsible for the Earth warming) because plants, when they grow, remove from the atmosphere the main element responsible for this It is made. The element to which the text above refers is part of the cycle:
a) of nitrogen
b) carbon
c) of phosphorus
d) of water
e) ozone
b) carbon
(UFRGS/2009) - Living beings maintain constant exchanges of matter with the environment through processes known as biogeochemical cycles.
Based on biogeochemical cycles, tick with V (true) or F (false) the following statements.
( ) The atmosphere is the main reservoir of carbon, nitrogen, phosphorus and oxygen.
( ) In the water cycle, evaporation is lower in the oceans, while precipitation is lower on the land surface.
( ) Atmospheric nitrogen (N2) is incorporated into organic molecules through foliar absorption.
( ) All organic molecules of living beings have carbon atoms in their composition, and their return to the cycle can occur through decomposition processes.
The correct sequence for filling the parentheses, from top to bottom, is:
a) V - F - V - V
b) F - F - F - V
c) V - V - F - F
d) F - V - F - V
e) V - F - V - F
b) F - F - F - V
(UDESC/2009) - Regarding biogeochemical cycles, analyze the following statements:
I. In the carbon cycle: carbon chains form organic molecules through autotrophic beings through photosynthesis, in which carbon dioxide is absorbed, fixed and transformed into organic matter by producers. Carbon returns to the environment through carbon dioxide through respiration.
II. In the oxygen cycle: Oxygen gas is produced during the construction of organic molecules by respiration and consumed when these molecules are oxidized in photosynthesis.
III. In the water cycle: solar energy plays an important role, as it allows liquid water to evaporate. The water vapor, in the higher and colder layers, condenses and forms clouds that, later, precipitate in the form of rain, and the water from this rain returns to the ground forming rivers, lakes, oceans or even infiltrating the ground and forming the sheets water tables.
IV. In the nitrogen cycle: one of the steps is nitrogen fixation, in which some bacteria use nitrogen and make it react with oxygen to produce nitrite, which will be transformed into ammonia in the process of nitrification.
Check the correct alternative.
a) Only statements II and IV are true.
b) Only statements I and II are true.
c) Only statements I, III and IV are true.
d) Only statements II, III and IV are true.
e) Only statements I and III are true.
e) Only statements I and III are true.