Water, Carbon, Nitrogen, & Phosphorus Cycles

Water, Carbon, Nitrogen, & Phosphorus Cycles

Also called Hydrologic cycle.

Heat from the Sun “drives” the cycle.

Precipitation: snow, rain, sleet, hail

Evaporation: liquid to gas (from lakes and oceans to form clouds)

Condensation: gas to liquid (water vapor in clouds increases to form rain…)

Water Vapor

Most comes from oceans; a major greenhouse gas.

Also comes from trees and plants from transpiration.

Transpiration

Loss of water vapor from the leaves of plants.

Water vapor increases to also form clouds and eventually rain.

Respiration

NOT respiration as in breathing.

Cellular level - when organisms break down food, water is a by-product which is released.

Recycles Hydrogen and Oxygen

Transfers from living and nonliving parts of the ecosystem

All organic

material

contains

carbon

Decomposition

Recycles carbon

Decomposers (microorganisms) break down organic matter (carbon) and returns it to the environment

Food

Food that we eat is broken down and the carbon is stored or used to build tissues.

Also is used for energy or released as methane.

Combustion

Important part of the cycle.

When wood or fossil fuels are burned, carbon dioxide is released.

Weathering

Rocks that contain carbon include “carbonates” such as limestone.

Weathering of limestone releases carbon.

Photosynthesis: CO2 sugar (C6H12O6)

Respiration: sugar (C6H12O6) CO2

Decomposition: carbon compounds returned to environment

Digestion: from food – stored in tissues or released

Combustion: burning wood or fossil fuels CO2

Weathering: breaking down some rocks like limestone releases

carbon

Nitrogen is important for your body: a part of DNA; in amino acids which make up proteins

Air

About 78% of the air we breath is nitrogen but we can’t directly use this.

Nitrogen gas has to be “fixed” first.

Nitrogen Fixation

Combining nitrogen in the air with other elements to form useful compounds.

Some microorganisms can do this; also can be done by lightning.

Nitrogen Fixation

Can occur in some bacteria in soil.

Mostly occur in bacteria found in “nodules” on legumes (peanut, peas, alfalfa and bean plants).

Nitrogen Fixation

Nitrogen-fixing bacteria get food from the plants. Bacteria combine nitrogen gas with hydrogen to form ammonia and then nitrates that are used by the plants.

Nitrogen Fixation

When we eat plants we get a usable source of nitrogen which we can use.

Denitrification: release of nitrogen gas back into the atmosphere by breakdown of nitrogen compounds and ammonia by other bacteria.

Lightning

Plays a minor role in the nitrogen cycle.

Intense heat of lightning causes nitrogen to combine with oxygen to form nitrogen oxides. Falls to Earth in rain and is absorbed by plants.

Nitrogen Cycle Summary

Air = 78% Nitrogen, can’t use it

Nitrogen Fixation – microorganisms make unusable nitrogen into compounds we can use

Animals eat plants to get nitrogen

Decomposers: break down dead organisms, return nitrogen to soil

Mainly held in rocks and released from weathering.

Plays a major role in plant growth.

Is confined only to a local ecosystem.

Is not recycled globally.

Important in body components such as DNA and in energy molecules (ATP).

A MAJOR

energy

molecule

Taken up by plants

Plants eaten by animals

Decomposition: returns phosphorus to soil

When removed from area, phosphorus is depleted (moving food to cities, runoff, etc.)