Class Notes (1,015,231)
CA (583,803)
McMaster (47,567)
ENVIRSC (405)
Lecture 3

ENVIRSC 2EI3 Lecture Notes - Lecture 3: Cellular Respiration, Biochemical Oxygen Demand, Nitrogen Cycle

8 pages32 viewsFall 2016

Department
Environmental Science
Course Code
ENVIRSC 2EI3
Professor
Luc Bernier
Lecture
3

This preview shows pages 1-2. to view the full 8 pages of the document.
Module #3: Ecosystems and Matter Cycling
Unit #1: Biogeochemical Cycling of Matter
What is Matter?
Earth’s supply of energy = infinite
Earth’s supply of matter = limited to what now exists
Law of Conservation of Matter: Cannot be created or destroyed
o Atom: exhibits characteristics of an element
o Subatomic particles: Each have different electrical charges
Protons
Neutrons
Electrons
Molecules = more than one atom joined together
o Compound = When two or more come together
Four Major Compounds: Make up living organisms
o Fatty Acids
o Carbohydrates
o Proteins
o Nucleic Acids
Matter exists in 3 types of states:
o Solid
o Liquid
o Gas
Matter can transform states by changes heat and/or pressure
Matter Cycling in the Ecosphere
Most critical environmental challenges facing earth = cycles of disturbances,
global warming, acid deposition, and spread of oceanic dead zones
Understanding nature of biogeochemicals = necessary to be able to fully
appreciate the nature of these problems and potential solutions
What are Biogeochemical Cycles?
Paths taken by matter while is has been cycling among: the different
components of the ecosphere
The biological, chemical and geological processes and components by which
materials cycle through ecosystems
o Generalized models of these cycles and help understand complexity of
Earth’s processes
o Nutrients = stored in compartments, often large, slow moving abiotic
pole and will move between compartments leading to rapid
interactions between abiotic and biotic components as part of these
exchange pools
You're Reading a Preview

Unlock to view full version

Only half of the first page are available for preview. Some parts have been intentionally blurred.

What are Nutrients?
Matter cycles through components of the ecosphere
o These cycles = essential to life
o Involve nutrients which are elements necessary for life
Macronutrients = needed in large amounts by all organisms
Micronutrients = required in small amounts by most species
Biogeochemical Cycles
Ecosystems vary substantially in terms of the speed of cycling and the
proportion of nutrients in each compartment
Ex: Compare temperate forest to tropical forest
o Speed of cycle may change depending on seasonal changes and the
type of nutrient
o May take 300 years for an atom of carbon to pass through the entire
carbon cycle
Residence time = the typical length of time something stays in
one compartment (ex: carbon dioxide stays in the atmosphere
an average of 5-7 years)
Detritus food chains are the main means in which nutrients in the biotic
component of the atmosphere are recycled, to the abiotic component for
future re-use
o Decomposer organism = fungi, earth worms, slugs, snails, beetles,
termites, ants
Atmospheric Reservoir
o Under natural conditions recycling rates between components
achieves a balance over time where inputs and outputs are equal
o Many pollution problems result from human induced accumulation in
one or more components of a cycle that is too great for natural
process to dissipate
Gaseous Cycles
Have most of their matter in the atmosphere
o Cycles can be classified according to the main source of their matter
Sedimentary Cycles
Have most of their matter in the lithosphere
Tend to recycle more slowly than those in gaseous cycles
Elements may be locked in geological formations for millions of years
Cycles mobilize materials from the lithosphere to the atmosphere and back
to the lithosphere
Unit #2: Phosphorus and Sulfur Cycles
Sedimentary Cycles: Phosphorus (P)
Phosphorus = macronutrient
You're Reading a Preview

Unlock to view full version

Only half of the first page are available for preview. Some parts have been intentionally blurred.

o Incorporated into many organic molecules
o Essential for metabolic energy use
o Critical that phosphorus cycles efficiently through compartments
Often the dominant limiting factor in fresh water aquatic ecosystems and for
plant growth in terrestrial soils
Main determinant of global futures
Availability of Phosphorus in the soil is influenced by acidity gets bound into
insoluble compounds under very acidic and basic conditions, therefore acid
precipitation limits phosphorus availability
Rocks in the earth’s crust are the main reservoir of phosphorus
o Animal waste and decomposition are also a large source of
phosphorus to soils
Bacteria mineralizes phosphorus in soil back into inorganic phosphate
making it available to plants and transported through water
o Transport of phosphorus or other nutrients by streams into lakes and
oceans increases the productivity of estuaries and other coastal
ecosystems and enter the food chain by uptake from phytoplankton
o Guano = Marine bird droppings
Returns phosphorus from marine food chain back to land
Main source of phosphorus for use of fertilizers
Mining
o Humans interfere in the phosphorus cycle by mining phosphorus-rich
rocks for fertilizers and detergents leading to excess phosphorus in
run off
Erosion
o Removing biomass leading to erosion and phosphorus in run off
Animal Wastes
o Concentrating organisms that produce phosphorus in waste like cows,
pigs and ourselves, leading to waste and phosphorus in run off
o By removing phosphorus from oceanic systems through fishing
leading to more inputs of phosphorus to fresh water and ultimately to
marine systems again
o Result = Eutrophication from excessive phosphorus accumulation on
fresh water systems
Sedimentary Cycles: Sulphur (S)
Differs from phosphorus in two ways
o Has atmospheric component and better recycling potential
o Has strong dependencies on microbial activity
Necessary component for all life and the building component of proteins
Not available in lithosphere but is stored over long periods in oceans
o Must be transformed into sulphate by bacteria to be absorbed by
plants
The form of sulphur in soils depends on the conditions
You're Reading a Preview

Unlock to view full version


Loved by over 2.2 million students

Over 90% improved by at least one letter grade.