Bio-geo chemical cycles in nature - class-IX

The oxygen cycle describes the movement of oxygen within and between the three main reservoirs of the Earth: the atmosphere, the biosphere, and the lithosphere.

Some bacteria maintain the soil fertility and others enhance it. The fertility of the soil is proportional to the nitrogen content. Nitrogen is an important ingredient in the structure and function of the living beings. Nitrogen-fixing bacteria like Azotobacter, Clostridium live free in the soil and fix atmospheric nitrogen. Rhizobium like bacteria live symbiotically with root systems of leguminous plants and fix from the atmospheric nitrogen. Therefore, the correct answer is option B.

Azotobacter can act both as symbiotically and non symbiotically to increase soil fertility. It Infuse the soil with antibiotic pesticides and inhabit the spread of soil borne diseases like pythium and phytophthora.

The Earth's atmosphere is composed of approximately 78% nitrogen, 21% oxygen, and 1% other gases including argon and carbon dioxide.

Azotobacter is a heterotrophic free living nitrogen fixing bacteria present in alkaline and neutral soils.

Sedimentary cycles involve elements that spend most of their time in the Earth's crust. Both the sulphur and phosphorus cycles are classified as sedimentary cycles, as their main reservoirs are rocks and soil.

Joseph Priestley is widely credited with the discovery of oxygen in 1774 after his experiments with mercuric oxide.

Burning fossil fuels releases large amounts of stored carbon into the atmosphere as carbon dioxide, which directly impacts the carbon cycle.

Nitrification is a two step process of converting ammonia into nitrites and nitrites into nitrates. Bacteria converting ammonia into nitrites includes Nitrosomonas. Bacteria converting nitrites to nitrates includes Nitrobacter.

Plants perform photosynthesis, which consumes carbon dioxide and releases oxygen. Deforestation reduces the number of plants available to produce oxygen.

Ground-level ozone is a secondary pollutant formed by the reaction of nitrogen oxides and volatile organic compounds in the presence of sunlight, both of which are primarily emitted by fossil fuel combustion.

Phosphorus is a critical component of ATP, which is the primary energy carrier in cells, and it is essential for the process of photosynthesis in plants.

Chlorofluorocarbons (CFCs) were widely used as refrigerants, propellants, and foam-blowing agents before they were phased out due to their ozone-depleting properties.

Acidification of water bodies, often caused by acid rain, increases the solubility of aluminum, which is toxic to fish like brook trout by irritating their gills.

In the ocean, carbon dioxide dissolves in water to form carbonic acid, which then dissociates into bicarbonate and carbonate ions, with bicarbonate being the most abundant form.

Tropospheric ozone is a pollutant formed by the reaction of nitrogen oxides and carbon monoxide in the presence of sunlight.

Natural sources of carbon monoxide include volcanic eruptions, forest fires, and the oxidation of methane in the atmosphere.

The consumption of carbon dioxide by plants is influenced by various factors including the leaf boundary layer, stomatal conductance, and the energy balance (radiation exchange).

The air in our atmosphere is composed of molecules of different gases. The most common gases nitrogen  (78%), oxygen (about 21%), argon (almost 1%) and carbon dioxide (0.03%). Other molecules are present in  the atmosphere as well, but in very small quantities. Composition of air is measured in percent by volume,  at sea level at 15C and 101325 Pa.

Photochemical phase includes photolysis of water and production of assimilatory power (ATP and NADPH). It liberates O2  during photolysis of water. 

The formation of hydrocarbons from organic matter (kerogen) in sedimentary rocks occurs through a process called catagenesis, which is driven by elevated temperatures and pressures over geological time.