Nutrient Cycling: Nitrogen and Carbon

• Nutrient flow occurs in an ecosystem

Nitrogen Cycle

• Major pathways include: nitrogen fixation, nitrification, ammonification, assimilation, and denitrification

Carbon Cycle

• The carbon cycle is the movement of carbon from the atmosphere into organisms and back
• The carbon cycle can exist in different compounds in plants, animals, rocks, liquids, sediments, and air
• Oceans are the major reservoir of CO2, containing as much as 50 times more carbon than the air
• Carbon can be stored in oceans as bicarbonate mineral deposit on the ocean floor
• The ocean regulates the CO₂ levels in the atmosphere
• The carbon cycle operates through CO2 exchange among the atmosphere, biosphere, and the oceans
• Green plants take in carbon in the form of CO2 as a raw materials for photosynthesis
• Green plants output carbohydrates and other organic substances
• A portion of carbon is deposited as fossil fuel, like coal or oil
• Carbohydrates and other organic substances move through the food chain
• CO₂ is liberated back into the atmosphere from burning fuel, respiration, volcanoes, and decomposition of organic waste

Water Cycle

• Many processes are involved in the movement of water
• Evaporation is the process of surface water vaporising into the atmosphere
• Transpiration occurs when water vapour escapes through the stomata to the atmosphere
• Evaporation and transpiration contribute to a large percentage of water in the atmosphere
• Sublimation occurs when snow or ice changes directly into water vapour without becoming water
• Condensation occurs when the water vapour cools down due to low temperatures at high altitudes
• Condensation leads to vapours becoming tiny droplets of water and ice, eventually forming clouds
• Precipitation is condensed water droplets in the atmosphere falling back to the ground as rainfall
• Infiltration/percolation is when precipitated water (rainwater) gets absorbed into the ground through the process of infiltration
• Runoff is rainwater which is not absorbed flowing down the sides of hills and mountains, eventually forming rivers

Ecological Factors

• Two categories of factors affect an organism in its ecosystem or habitat: Biotic and Abiotic
• Biotic factors affect living organisms e.g. competition, predation, pollination, parasitism, diseases, immigration, emigration
• Abiotic factors are non-living factors, including edaphic and physical factors
• Edaphic factors include factors which have to do with soil structure, soil types, soil conditions, and topography
• Physical factors include temperature, light, humidity, rainfall, turbidity, and wind

Temperature Measurement

• Temperature is the degree of coldness or hotness of a body
• Temperature affects the distribution of organisms in both aquatic and terrestrial habitats
• Temperature affects the physiology of organisms
• Temperature measured by mercury, soil, or maximum-minimum thermometers

Rainfall Measurement

• Rainfall affects the vegetation, animals and is important in all habitats
• The amount of rainfall is measured by a rain gauge

Light Measurement

• The source of light in an ecosystem is the sun
• Light affects both plants and animals in aquatic and terrestrial habitats because photosynthesis is involved
• Light intensity is measured by a photometer
• The amount of light is measured by a light meter

Relative Humidity Measurement

• Humidity is also known as, the concentration of water vapor in the atmosphere
• Relative humidity is the amount of water vapor in the atmosphere, expressed as a percentage of moisture that can be retained by the atmosphere
• Relative humidity is measured using a hygrometer

Wind Measurement

• Wind affects rainfall, moisture, temperature and consequently drives the distribution of organisms in habitats
• The direction of wind is indicated by a wind-vane
• The speed of wind is measured using an anemometer

Pressure Measurement

• Climatic and osmotic pressure places physiological constraints on organisms which fly and respire at high altitudes, or dive to deep ocean depths
• Air pressure is measured using a barometer (e.g. aneroid barometer)

Turbidity Measurement

• Turbidity is the amount of suspended particles in a water body
• Turbidity affects the transparency of water
• The clarity or haziness of water affects light penetration and the types of organisms in the aquatic environment
• Turbidity is measured using a secchi disc