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BIOL 3450 Final Review.docx

Course Code
BIOL 3450
Beren Robinson
Study Guide

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BIOL 3450 Final Review
Lecture 1 – Water world
Where did our water come from?
o2 theories:
Volcanism: heat-driven chemical reactions in the mantle interior
combined H and O2 to make water that continues to be released at
the surface by volcanism
Approximately 0.1-0.5% of mantle rick is water weight.
This accounts for 3-16x the amount of water in the oceans
right now
Volcanoes (active or not) release 1000s of tons of gases into
the atmosphere per day. 70% of this is water. Over 4 billion
years, this could fill the oceans approximately 100 times
Comet hypothesis: ~ 20 comets of average 10kg mass hit out
atmosphere each minute, equaling 10 million per year. Comets
have a lot of icy water that is deposited into the atmosphere upon
Only about 0.0025mm of water per year, but this could fill
the oceans 2-3x over the lifespan of the earth
oBoth of these processes have contributed to Earth’s water, but their
relative contributions are unknown
Hypsographic curve:
oShows relative proportions of land above and below water
oMean height of continents = 0.8km
oMean ocean depth = 3.7 km
Dynamic flow
oWater on earth isn’t still. 300,000 km3 moves between reservoirs per year
oAmount of water is approximately constant
Hydrological cycle must balance addition and removal

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oAt the surface, wind causes horizontal mixing of waters
oCoriolis effect causes water to move clockwise and counter-clockwise in
the northern and southern hemispheres respectively
This creates oceanic gyres that circulate surface pelagic waters in
the N and S of each ocean basin
oCold seawater sinks  19 million m3/minute of water cools and sinks in the
North Atlantic alone (downwelling)
The cold, dense water moves slowly to the equator
Water in the N. Atlantic eventually resurfaces in the N. Pacific
(1200 years later)
This sinking transports nutrients into the deep waters, warms the
North and cools the equator
oUpwellings of warmed water go to the surface, providing nutrients to the
surface waters. This causes PP blooms from August to October
Water Chemistry
oWater is a great solvent since its covalent bonds are extremely strong
It can ionize other molecules when the strength of its H-bonds
exceeds the strength of the bonds holding the other molecules
Ionizes salts and other compounds into ions in the water (Na+,
Ca2+, Cl-…)
oThe proportions of dissolved materials in world oceans is remarkably
constant, indicating mixing
Conductivity can be used to measure salinity (more salts, more
oWater is constantly disassociating and reassociating itself to.from its ions.
There is a general proportion of H+ and OH- in water at a given time,
which determines the pH. It differs between bodies of water due to many

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Second most important dissolved compounds in water are gases
O2 for respiration, CO2 for photosynthesis
Both come mainly from the atmosphere, but are also
recycles within the water
Diffusion across the air-water boundary is slow
Waves and turbulence increase mixing of these gases
As physical mixing declines, biological activity determines
their concentrations
Temperature, pressure and salinity also affect
Algae blooms or large plant beds raise O2 by day and raise CO2
by night
oTypical pHs
0-2  some volcanic lakes
2-6  many bog lakes
7-10  productive hard-water lakes
8  oceans
>10  few alkaline desert lakes
oOrganism pH preferences
<2  some fungi, bacteria
2-6  fungi, bacteria, some zooplankton
6-9.5  most zooplankton, fish and other animals
>8  most molluscs, most bacteria (low pH dissolves Ca2+ shells
of molluscs)
>10  bacteria, but few multicellular organisms
oSome waters can absorb or neutralize H+ without changing pH
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