Transcript cycles and biomes1x

The Cycling of Matter
• To understand how matter cycles through
ecosystems, you must understand the cycling of
organic substances in living things.
• The materials stored in living things comes from a
limited amount of matter.
• Therefore, all matter must be recycled. This
recycling of matter involves the carbon, oxygen
and nitrogen cycles as well as the role of
decomposers.
• All matter tied up in the bodies of organisms
must be decomposed and recycled.
• organic substance- compound that always
contains carbon and hydrogen atoms, and
often oxygen and nitrogen atoms. e.g.
proteins, sugars,
– e.g. C6H12O2, CH4
• inorganic substance - compounds that don’t
contain a combination of hydrogen and
carbon.
– e.g. CO2 , H2O
Carbon Cycle
• carbon is the main atom of all living things. In inorganic
form it mainly exists as carbon dioxide gas in the air.
CO2 is also dissolved in sea water.
• plants use carbon during photosynthesis to make
carbohydrates. This takes carbon from its inorganic
state and transforms it into organic compounds. This
carbon then gets passed up the food chain
• carbon is returned to its inorganic state when
organisms digest food to get energy. Consumers use
sugars in a cell reaction process called cellular
respiration.
• Cellular respiration requires oxygen. This reaction
releases energy to the body and gives off inorganic
carbon dioxide to the air.
• Decomposer organisms also release carbon dioxide to
the air
• some carbon has become buried as coal. This carbon is
locked away out of circulation unless humans release it
by burning fossil fuels (gas, oil, coal).
• These fossil fuel deposits, the ocean and boglands are
huge reservoirs of carbon which are released slowly to
the atmosphere.
Human Impact on the Carbon Cycle;
• the level of CO2 in the atmosphere is rising
quickly way beyond normal levels. This is due to:
• 1. carbon released from natural reservoirs faster
than normal due to burning of fossil fuels,
burning forests.
• 2. less CO2 being removed due to removal of
plants to clear land for agriculture, forestry or
building.
• The result has been global warming
Global Warming
• global warming - a warming trend in our climate caused by
excess greenhouse gases such as carbon dioxide.
• Greenhouse gas - any atmospheric gas that traps heat and
adds to the greenhouse effect.
– e.g. carbon dioxide.
• CO2 in the atmosphere provides a natural “greenhouse
effect”. It traps reflected solar energy and warms the earth.
However, since humans have increased the amount of CO2
in the atmosphere, we are causing too much heat to be
trapped and it is changing our weather patterns and
climate. The average global temperature is rising.
Global Warming
• Enhanced Global warming is the term given to describe the
recent increase of the earth’s temperature as a whole.
• The earth’s weather and climate is controlled by energy from
the sun, which warms the surface of the earth as it, in turn,
deflects the energy back into space.
• Some of this deflected energy is retained within the
atmosphere of the earth by greenhouse gases which prevent
the energy from passing into space, thereby preserving heat.
• It is this process that results in the earth having a temperature
which supports life.
• Global warming has occurred since the 1980's, and during this
time, the seven warmest years in global meteorological
history have been recorded.
Global Warming
• If the earth's warming trend continues into the next
decade the earth may enter a period of climate
change unlike any of the past.
• Changes in the concentration of heat-trapping gases
"greenhouse gases" have played a major role,
because these gases trap the heat and does not let it
escape, therefore causing global warming or an
increase in climate temperatures.
Global Warming
• The three primary greenhouse gases which are
responsible for this warming include carbon dioxide,
methane, and nitrous oxide, all of which naturally
exist in the earth’s atmosphere.
• These three gases are required in order for the
natural process of temperature control to occur.
• The problems arise when there is a surplus of these
gases in the atmosphere.
Global Warming
• Causes of excess greenhouse gases include:
• Carbon dioxide is released into the atmosphere by the
combustion of solid waste, fossil fuels, wood and wood
products.
• Methane emissions are a direct result of the production and
transportation of coal, natural gas, and oil. The raising of
livestock, and the decomposition of organic waste also
contribute to the amount of methane emitted into the
atmosphere.
• Nitrous oxide emissions are a result of agricultural and
industrial activities as well as the burning of solid waste and
fossil fuels.
Global Warming
• There are also greenhouse gases which do not occur
naturally, that are generated by human activity.
Examples of these gases include;
chlorofluorocarbons found in refrigeration devices,
hydrofluorocarbons, and perfluorocarbons.
• Each varies in their heat trapping ability and
combined with those gases originally present in the
atmosphere, serve to retain a sufficiently larger
amount of heat then would naturally be retained.
Global Warming
• Many people today may be unaware of the drastic
effects which global warming can have on our
environment,
• These people are ignorant to the facts about this
issue, and what these changes will mean to people
all over the world.
• Because of the projected increase of the overall
global temperature, climates around the world will
likely to be affected.
• This could cause major disruptions to the
environment.
Global Warming
• A major issue which is causing concern is that of our own
health.
• Throughout the world, the occurrence of particular diseases
and other threats to human health depend largely on the local
climate. For example:
• extreme temperatures can directly cause the loss of life
(although it has the greatest toll on very old and very young
people),
• many severe diseases are only found in warm areas,
• and as well warmer temperatures have been shown to
increase air and water pollution.
Global Warming
• Increasing temperatures may also increase the risk of
infectious diseases, which only occur in warm areas,
such as malaria, dengue fever, yellow fever, and
encephalitis.
• These diseases which are spread by mosquitoes and
other insects could become more common if warmer
temperatures allowed these insects to inhabit places
farther north.
Your Turn
• Do questions p. 65, # 1, 2, 4, 6, 7 (a) (b) (c)
The Nitrogen Cycle
• Nitrogen is needed by all organisms to make proteins
(tissue) and DNA. 79 % of the air is nitrogen gas but plants
and animals cannot get their own nitrogen from the air.
• Only plants can use inorganic forms of nitrogen such as
nitrates, NO3 , found in the soil or dissolved in water, and
extract - the nitrogen in them to use in making their own
plant proteins.
• All consumers must consume other organisms to get their
proteins.
• When organisms die, the nitrogen present in the proteins
of living things gets recycled back into inorganic forms such
as ammonia, nitrites and nitrates by the processes of
decomposition and denitrification.
• Nitrogen - fixation stage
• nitrogen fixation - the process of converting free atmospheric
nitrogen into nitrates.
• Nitrogen gas in the atmosphere gets converted into nitrates, NO3 .
These are absorbed by the - roots of plants. This can occur in two
ways:
• (1) lightning in the atmosphere - causes nitrogen in the air to react
with oxygen to form nitrates.
• (2) Nitrogen - fixing bacteria - give off nitrates as a waste product.
Some nitrogen fixing bacteria are free - living but many live in the
roots of certain plants called legumes. They supply the legume
plants with a steady supply of nitrogen in return for shelter in the
roots and food. Legumes include beans, alfalfa and clover - type
plants
Man’s Impact on the Nitrogen Cycle;
• We are adding extra nitrogen to many
environments in the form of fertilizers and
pollution wastes from many industries.
• Human sewage is often released into rivers with
little treatment(e.g. Montreal into the St.
Lawrence River) and act as fertilizer.
• Normally, there is a balanced amount of nitrate in
an aquatic ecosystem. However, in areas near
agricultural lands where lots of fertilizers are
used, runoff into rivers have caused the levels of
nitrate in lakes to get too high.
• this causes a process called eutrophication - pollution
making a lake richer in nutrients.
• If the level of nitrate gets too high, an algal bloom can
occur. This is where the algae population grows out of
control, scumming over much of the lake’s surface.
• The algae, too many in number, block much of the light
from reaching other plants growing underwater.
• Also, when the algae die, the decomposer bacteria in
the water have lots of food. This causes their
population to increase.
• All this extra decomposition uses up much of
the dissolved oxygen in the water. This is very
unhealthy to the ecosystem.
• It has a bad effect on many species, causing
their numbers to decline. Fish and other
aquatic animals may begin to die.
Decomposition stage
• Decomposer bacteria decay dead organisms.
They break down the proteins in the dead
organisms to produce ammonium.
• Other bacteria in the soil convert ammonium
into nitrites. Another type of bacteria convert
the nitrites into nitrates, becoming available
again for plant use.
Denitrification stage
• Some of the nitrates in the soil is converted
back into free nitrogen gas by certain bacteria
called denitrifying bacteria. This returns
nitrogen to the atmosphere.
Your Turn
• Do -questions, p. 69, # 1 - 4 and p. 71, # 3,4
Question 1
• Explain why nitrogen is important to
organisms.
• Organisms require nitrogen to produce
proteins and nucleic acids.
Question 2
• Nitrogen must be converted to nitrates before
it can be used by organisms
• If the soil lacks nitrogen – fixing bacteria this it
has few nitrates for the plants to take in
Question 4
• The bacteria convert nitrogen to nitrates from
the plants and the plants provide sugar from
photosynthesis for bacteria
Question 6
• Aerating lawn exposes denitrifying bacteria to
oxygen and so reduces the breakdown of
nitrates to nitrogen.
• The soil is able to retain the nitrates that
would otherwise be lost
Question 10
• Clover grows in the older lawns because of the
abundance of denitrifying bacteria. The
bacteria in clover roots would benefit the
lawn by providing more nitrates.
Question 3
• Algae blooms occur in spring as a result of
spring runoff containing nitrates and nitrites
• Algae blooms promote an increase in
herbivorous plankton and other organisms
that can eat plankton. When the algae die the
resulting increase in decomposers can cause
oxygen depletion that can kill fish
Question 4
• High nitrate levels in drinking water can pose a
problem for infants because their stomachs
are not a s acidic as those of adults. Bacteria
that convert nitrates to nitrites in the
intestines and enter an infants less acidic
stomach. The nitrates can inter the blood
stream and bind to the hemoglobin.
The Oxygen Cycle
• Oxygen is cycled between the atmosphere and living
(biotic) things. Oxygen is used in the process of cellular
respiration by both plants and animals. Carbon is
released in the form of CO2 as a waste product of this
reaction.
• Plants take in the inorganic gas CO2 and use it in the
process of photosynthesis to make organic sugars such
as glucose, C6H12O6. Oxygen is released as a waste
product of the photosynthesis reaction.
• The reactions of cellular respiration and photosynthesis
are reciprocals of each other. The reactants of one
reaction are the products of the other reaction.
Photosynthesis:
CO2 (g) + H2O (l) → C6H12O6 (s) + O2 (g)
Cellular Respiration:
C6H12O6 (s) + O2 (g) → CO2 (g) + H2O (g)
• C6H12O6 (s) + O2 (g) → CO2 (g) + H2O (g)
Reaction
Reactants
Products
Photosynthesis
Carbon dioxide + water
CO2 + H2O
glucose sugar + oxygen
C6H12O6 + O2
Respiration
glucose sugar + oxygen
C6H12O6 + O2
Carbon dioxide + water
CO2 + H2O
Human Impact on the Oxygen Cycle
• Deforestation is the major impact by man.
Trees are the earth’s largest oxygen –
producing plants. Plants give off O2 to the
atmosphere through photosynthesis. The
destruction of forests lowers the amount of
CO2 which is being converted into O2. The
reduction in trees is a one of the contributing
factors to global warming.
Ozone
• Ozone is a form of oxygen
• In the atmosphere oxygen is found in three
forms O, O2, O3
• Ozone is formed when a solar ray hits a
molecule of O2 causing it to split apart
• If one of these free atoms hits another O2
molecule then ozone is formed
Ozone
• In the stratosphere oxygen is constantly being
bombarded by UV radiation, resulting in the
formation of ozone
• Ozone serves as a protection layer, filtering
out the harmful UV radiation
• In recent years human activity has led to the
destruction of this layer and to the depletion
of the ozone layer
Ozone
• Ozone's unique properties allow it to act as a
protective layer around the earth
• It acts as a sunscreen, filtering out the
damaging UV rays
• This layer is the thickest at the poles and
thinnest at the equator
• Even though the radiation is strongest at the
poles, stratospheric winds carry the ozone
towards the poles
Ozone Depletion
• Chlorofluorocarbons (CFC’S) account for
approximately 80% of the stratospheric ozone
depletion
• Other compounds that cause ozone depletion
are : halons, carbon tetrachloride, methyl
chloroform, and methyl bromide
• These are called industrial halocarbons
• These compounds are used in refrigerators,
furniture foam and fire extinguishers
Ozone Depletion
• Human activity such as deforestation, fertilizer
use and fossil fuel combustion have also
contributed to the loss of ozone
The Effects of Ozone Depletion
• Not yet fully understood
• We know they are potentially severe
• Ozone warms the stratosphere, but due to
decreasing ozone in the stratosphere, the
stratosphere is cooling
• CO2 in the atmosphere is increasing, trapping
heat in the troposphere, adding to the cooling
effect of the stratosphere
Ozone Depletion and Humans
• Skin cancer
• Eye damage and cataracts
• Immunospuression
Ozone Story
Your Turn
Case Study : The Effects of Deforestation on
Cycling
• p. 72 - 73 do items (b) - (g).
• p. 73, # 1 - 3.
The Biomes of Canada (read pp. 88 92)
• Biome - a collection of ecosystems that are
similar or related to each other, usually by the
types of plants present in the area.
There are 4 biomes present in Canada:
•
•
•
•
1. Tundra
2, Boreal Forest
3. Temperate Deciduous Forest
4. Grasslands
Tundra
Abiotic Factors
Biotic Factors
Very low temperatures for most of year
Rapid flowering plants
Short growing season
Mosses and lichens
Permafrost below soil
Caribou, ptarmigan, lemmings
Low precipitation
Poor soil quality
Active layer – the layer that thaws in summer
to provide nutrients to plants
Slow decomposition due to cold
temperatures
Boreal Forest Biome
Abiotic Factors
Biotic Factors
Warmer than tundra
Coniferous trees
Changeable weather
Seed eating birds, squirrels, deer
Soil contains some water and is acidic
Conifer trees dominate because well
adapted to conditions ( waxy cuticle, small
surface area, slow shedding, pyramid shape
and flexible branches))
Precipitation is 40 cm/year +
Limited food source for animals living on
forest floor thus not great biodiversity
Very acidic soil due to conifer needles
Make up 80% of forests in Canada
Temperate Deciduous Biome
Abiotic Factors
Biotic Factors
Longer grow season than boreal forest
Deciduous trees
Higher temperatures than tundra or
boreal forest thus faster recycling of
materials
Many shrubs and ferns
Fertile soil
Many insects
Precipitation 100cm/year +
Deer, black bear, shrews, mice
Wide ecotone
Shift in types of plants and animals as you
move from north to south
Great biodiversity
Grassland Biome:
Abiotic Factors
Biotic Factors
Longer growing season than boreal forest
Fescue grass
Temperature higher than tundra or boreal forest
Grasshoppers, bison, snakes,
hawks
Rich, fertile soil
One layer thus low biodiversity
Precipitation from 25 to 75 cm/year
Abiotic factors much the same as deciduous
forest except less precipitation
Fires act as decomposers