Because you CARE....

This is the homework that I was supposed to be doing during my first post. Now I'm just spamming my own blog to make it look like I actually have a life - which I don't.

Biogeochemical Cycles, the Greenhouse Effect, & Ozone Layer Depletion

Carbon Cycle

Carbon
· resides in atmosphere as CO₂

· is taken from atmosphere for use in photosynthesis

→ plants, cyanobacteria, algae

→ carbon from plants etc. passed up the food pyramid when plants are eaten by primary consumers, which are eaten by secondary consumers, and so on.

· is released back into atmosphere as CO₂ by plants etc. as a byproduct of ACR

· is released back into atmosphere as CO₂ by consumers who have eaten plants, or consumers who have eaten other consumers, as a byproduct of ACR

· is released back into atmosphere as CO₂ when wood and fossil fuels are burned.

→ fossil fuels formed from dead plant matter (coal, eg.)

· is released back into atmosphere as CO₂ when dead plant & animal matter is digested by detritivores (bacteria, eg.)

Nitrogen Cycle
Nitrogen

· resides in atmosphere as N₂

· enters ecosystems as NH₄⁺ and NO₃^- (only 5-10% of usable nitrogen) by the process of atmospheric deposition

→ dissolved in rain, or as fine dust

· enters ecosystems through nitrogen fixation (as ammonia – NH₃)

→ done by specific bacteria – symbiotic (in/near roots of plants – legumes especially) & nonsymbiotic (free-living, in soil)

→ ammonia picks up an H⁺ to become ammonium (can be used by plants directly)

→ most ammonium is used by bacteria as an energy source through nitrification, which oxidizes it to nitrite, and then to nitrate

· can be fixed into nitrate during a lightning strike

· is taken up by plants as nitrate

· is consumed by animals via plants

· is returned to soil by the decomposition of dead plant and animal matter by detritivores

· can then undergo ammonification, which returns it to ammonium

· also undergoes denitrification, which returns it to the atmosphere

Water Cycle
Water

· resides in atmosphere as water vapor

→ condenses to form clouds

· falls as rain/other precipitation from clouds

→ drains into soil, lakes, & rivers which in turn drain into the ocean

· is taken up from soil by plants

· reenters atmosphere through transpiration in plants

· is taken up from rivers & plants by animals

· reenters atmosphere through respiration in plants & animals

· reenters atmosphere through evaporation from lakes, rivers, the ocean, puddles, ponds, etc.

Phosphorus Cycle
Phosphorus

· resides in soil and rocks – does not have a gaseous form, unlike carbon & nitrogen

→ weathering of rocks adds phosphorus to soil

· is taken up from soil by plants to be incorporated into organic molecules such as DNA

· is taken up from plants by consumers

· is returned to soil by the excretions of animals and the action of detritivores on dead plant and animal matter

· leaches into the water table

· accumulates in sediments in rivers & oceans

→ can be returned to ecosystems through geological uplifting etc.

→ rocks formed are weathered, which returns phosphorus to the soil

Combustion of Fuels

Combustion of fuels

· releases CO2 into the atmosphere

· CO2 is a known greenhouse gas

· therefore there is a risk that global warming may occur as a result of human manufacturing and burning of fuels

· CO2 concentration in 1958=316 ppm

· current CO2 concentration=387 ppm

· Note: increasing CO2 levels increases the rate at which most plants will grow – except C4 plants.

→ this could have a major effect on many environments/plant populations

· CO2 is used in photosynthesis, then given off during respiration

→ release of CO2 into the atmosphere

· Dead/decaying plant & animal matter become fossil fuels, which are burned, or plant material is burned directly as wood

→ release of CO2 into the atmosphere

Greenhouse Effect
· The atmosphere is formed of many gasses (78% nitrogen, 21% oxygen, 1% argon, 0.04% carbon dioxide, among others)

· Greenhouse gasses = gasses in the atmosphere that absorb and emit infrared radiation (water vapor, carbon dioxide, ozone, and methane, eg.)

· The greenhouse effect is a change in the temperature of a moon or planet by the addition of an atmosphere which contains greenhouse gasses.

· The net effect of greenhouse gasses = to warm the surface of a planet or moon

· Levels of CO₂ in human-caused emissions have caused concerns about global warming

→ the greenhouse effect, which keeps Earth warm, may cause overheating if there's too much CO₂ in the atmosphere

Ozone Layer Depletion

· (O₃)

· resides mainly in a layer in the stratosphere

· protects the surface of the Earth from harmful UV radiation

· the ozone layer is becoming thinner as a result of the release of CFCs (chlorofluorocarbons), which reduce the O₃ to O₂

→ CFCs can affect up to one hundred thousand molecules of O₃ before their own degradation

→ even if all production of CFCs ceased immediately, they would continue to influence the ozone layer for another hundred years

· potential consequences of a thinning ozone layer include skin cancer, cataracts, negative effects on crops and communities of organisms