ENV100Y5 Lecture Notes - Lecture 14: Myostatin, Estuary, Water Cycle
Module 2: May 22-June 1
Date: Thursday, May 24
SESSION 15: EVOLUTION, BIODIVERSITY, AND POPULATION ECOLOGY (I)
Readings: Chapter 4
Humans Affect the Carbon Cycle
● Carbon mobilization
○ Burning fossil fuels (moving from geosphere to atmosphere)
○ Deforestation, burning of biomass (moving from biosphere to atmosphere)
○ Cattle and rice production (moving from biosphere to atmosphere
● Livestock produce 18% of greenhouse gases - more than the transportation section
● 1.5 billion cattle worldwide - impact of intensive livestock farming on the environment is
massive
● Atmospheric carbon dioxide reservoir: largest in the past 650,000 years
● Missing carbon sink: 1-2 billion metric tons of carbon are unaccounted for
● Plants or soils of northern temperate and boreal forests? Global warming is not evenly
distributed.
The Nitrogen Cycle
● Complex; many forms (species) of nitrogen
● N^2 - elemental, 80% of what you breath, 72% of atmosphere, but is biologically inert
● NH^3 (ammonia); nitrous oxides: NO2 (nitrite), NO3 Nitrate
● Largest reservoir is atmosphere; some in sedimentary rocks
Bacterially-Mediated Processes are Important in the Nitrogen Cycle
● Bacteria in the soil that live in plants → by eating plants or something that has eaten the
plants
● Nitrogen fixation = N2 → NH3 (ammonia) by nitrogen-fixing bacteria (chemical reaction)
Nitrification & denitrification
● Nitrification = ammonium ions → nitrite ions → nitrate ions
● Plants take up these ions; N enters food chain
● Denitrification = bacteria convert nitrates to N2, releasing it back into the atmosphere
● N is often limiting in ecosystems
Progressive Nitrogen Limitation Hypothesis
● Increasing carbon dioxide in the atmosphere may stimulate NPP, but soon soil depletion
of N will be a limiting factor
Humans Affect the Nitrogen Cycle
● Emissions of N-containing greenhouse gases & smog precursors from fossil-fuels →
acidified water and soils (HNO3 = nitric acid)
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ENV100Y5 Full Course Notes
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Document Summary
Session 15: evolution, biodiversity, and population ecology (i) Burning fossil fuels (moving from geosphere to atmosphere) Deforestation, burning of biomass (moving from biosphere to atmosphere) Cattle and rice production (moving from biosphere to atmosphere. Livestock produce 18% of greenhouse gases - more than the transportation section. 1. 5 billion cattle worldwide - impact of intensive livestock farming on the environment is massive. Atmospheric carbon dioxide reservoir: largest in the past 650,000 years. Missing carbon sink: 1-2 billion metric tons of carbon are unaccounted for. N^2 - elemental, 80% of what you breath, 72% of atmosphere, but is biologically inert. Nh^3 (ammonia); nitrous oxides: no2 (nitrite), no3 nitrate. Largest reservoir is atmosphere; some in sedimentary rocks. Bacterially-mediated processes are important in the nitrogen cycle. Bacteria in the soil that live in plants by eating plants or something that has eaten the plants. Nitrogen fixation = n2 nh3 (ammonia) by nitrogen-fixing bacteria (chemical reaction) Nitrification = ammonium ions nitrite ions nitrate ions.
