Biomagnification
- Toxic chemicals have recently been found in fish
- Toxic form of Mercury (Methylmercury). Chronic exposure
damages kidneys, liver, and nervous system. In pregnant women,
it can affect the development of the fetus’ brain.
- Mercury is known as a resistant chemical, which means that it
resists the decomposition by microorganisms and environmental
conditions; leaving them to remain in the environment for
decades.
- Most mercury found in the environment is from improper
disposal. (batteries, fluorescent lamps, burning hospital waste,
burning coal for fuel.)
- Naturally, mercury is found in rocks.
- Micro-organisms in aquatic systems convert elemental mercury to
methylmercury, which is easily absorbed by plants and animals.
- Methylmercury accumulates in the tissues of aquatic organisms,
thus biomagnification.
http://www.youtube.com/watch?v=xRqAS4Eow-c
Cycles of matter
- Organic matter: contains hydrogen and carbon. (proteins,
sugars, fats)
o Broken down and rebuilt to continue cycle of matter
- Matter has to be recycled
o Food is organic matter
 Digestion breaks down complex organic
molecules into simpler molecules
 Cells use simple molecules to build more
complex molecules your body structure needs
 Organic molecules are held in living things and
are released into the environment after death by
decomposers. They break down organic
molecules into inorganic molecules that pass
through soil and water to be reused at a later
time
Water cycle (Hydrological cycle)
Figure 2.2: page 35 (know this diagram)
http://www.youtube.com/watch?v=0_c0ZzZfC8c&feature=related
- Water is a polar molecule (The
oxygen end has a slight negative
charge, and the hydrogen end
has a slight positive charge)
- Because of this bonding of the hydrogen and oxygen,
water molecules interact through hydrogen bonding
o One hydrogen bonds to a nearby oxygen molecule
- Water is able to remain a liquid over a large temperature
range and it is able to dissolve and transport substances
because of the hydrogen bonds.
- Hydrogen bonds are weak individually. However, within
water molecules, they form, break, and re-form
frequently.
- Hydrogen bonds require energy to break the bonds. Only
when the bonds are broken, can water undergo a phase
change from a liquid to a gas.
- Cohesion: the attraction of water molecules to each other
o Responsible for surface tension (why insects can walk
on water)
o Also keeps organic debris on the water surface
http://www.youtube.com/watch?v=NVtPAaPRB3w&feature=list_related&playnex
t=1&list=AVGxdCwVVULXcN_oMbBuiFyh-hT_3DkTOQ
- Adhesion: the attraction of water molecules to molecules
of other substances
o Provides an upward force on water and counteracts
the pull of gravity
o Using cohesion and adhesion, water can travel from
the roots of a tree up to its leaves against the force of
gravity.
- Water also has a high heat capacity because of its
hydrogen bonding
o Allowing water to heat up more slowly, and hold that
temperature for longer periods
Seasonal Variations in Canadian Lakes
In Canada, the changing of the seasons causes significant
changes in the abiotic factors in freshwater ecosystems
found in our lakes. As water cools, it becomes denser,
just like other substances.
However, as water cools below 4°C a strange thing
happens – it starts becoming less dense. When water
freezes, it expands because hydrogen bonds hold the
water molecules in an open crystal structure. This is why
ice floats, forming a layer on top of cold water, and why
the lowest layer of water in a lake often has a
temperature of 4°C.
When ice melts at 0°C, its solid, crystalline structure
begins to break down. The loosened molecules pack
more closely together and fill in the space in the
collapsing solid structure. This increases the density of
water, until water reaches its greatest density at 4°C.
Again, this is why water at the bottom of a lake has a
temperature of 4°C.
Water’s density characteristics have key consequences
for life and the cycling of nutrients. In the spring, as
water is melting, it becomes denser as it warms until it
reaches 4°C. The denser water sinks below the less
dense and cooler water, leaving the cooler water at the
top to warm and subsequently sink.
Similarly, as winter approaches and the water
temperature cools towards 4°C, the cooler water
becomes denser and sinks below the warmer water.
When the warmer water cools, it sinks until it reaches its
maximum density at 4°C.
As water sinks and rises, nutrients and dissolved oxygen
are cycled with it.
Assignment:
Read page 35-40
Question 1 – 5 on pages 35 -40
Section 2.2 – Biogeochemical Cycles (Class Presentations)
Section 2.1 Review Questions #’s 2 - 9 on p. 40
Section 2.3
The overgrowth of algae, called an algal bloom, produces
large amounts of organic matter. As decomposers break
down the organic matter, they use up the oxygen in the
water, resulting in the death of fish and other aquatic
life.
Factors that contribute to algal blooms:
 Nutrients in the soil exposed by deforestation can be
washed into rivers by rain.
 Sewage that is discharged into bodies of water can
contain large amounts of phosphate and nitrates
which promote the growth of algae.
 Surface run-off and snow melt carrying manure from
livestock operations can add phosphate and nitrate
to bodies of water.
 Run-off from fertilized agricultural field and enter
bodies of water.
http://www.dailymotion.com/video/x21ifq_algalblooms_shortfilms
Read as a class pages 53 to 61 Complete p. 61 #’1-8
Assignment
Phytoremediation
 Read p.62 Complete 1-6 (Hand in)