Download The Biosphere

(1) WHAT IS THE BIOSPHERE?
- The living layer which includes all organisms & their habitat, that is:
lithosphere
(solid layer:
sediments & soil)
+
hydrosphere
(water layer: ice, glaciers,
seawater, freshwater)
+
atmosphere
(air layer)
(2) BIOGEOCHEMICAL CYCLES
- occurs when a life sustaining substance (ex. C, H2O, N, & P) cycles throughout the planet in an
expected way creating a perpetual multi step loop
- A biochemical cycle incorporates biological cycle (ex. photosynthesis, digestion…), geological
processes (ex. erosion, sedimentation…), & chemical processes (ex. synthesis, oxidation…)
- 3 cycles in this chapter: (1) carbon, (2) nitrogen, (3) phosphorous
2.1 CARBON CYCLE
- Carbon: element common to all living beings; building block for carb’s, prot’s, & fats; found in
import. gases (CO2, CH4); during cycle C travels through living & dead beings, atm., rocks, soil, &
ocean
- Fossil fuel has upset the natural C cycle balance, esp. since the beginning of the industrial era,
increasing CO2 & CH4 production in atm.
Carbon Cycle Components (reminder: all cycles loop; therefore there is no beginning or end just
movement)
1. Photosynthesis
-Pl. (producers) use CO2 from the atm. combined with solar ener. to produce glucose, used for
pl. cell development
2. Ingestion
-Herbivores & carnivores assimilate (eat) carbon in order to grow
3. Respiration
-Organisms exhale which releases some C (in the form of CO2) to the atm.
4. Decomposition of waste
-C not released through respiration is found in excretions (urine, feces, sweat) & in the form of
dead animals; these are broken down by decomposers which emit CO2 & CH4 in the process
5. Forest fires
-Combustion of wood transforms the C found in leaves & branches into CO2
6. Shells & skeletons
-Some of the CO2 that dissolves in oceans reacts with calcium forming calcium carbonate
(CaCO3) a building block of marine organism skeletons & shells
7. Carbonate rock
-CaCO3 found in skeletons & shells of dead & decomposing marine organisms form marine
sediments which are compacted over time yielding carbonate rock; through tectonic activity,
some of this rock is brought back to the surface
8. Volcanic eruption
-During volcanic eruptions certain carbonate rocks can be melted by hot magma transforming
some of the C in the rock into atmospheric CO2
9. Fossil fuels
-Dead organisms decompose & get compacted under layers of sediments; over hundreds of
millions of yrs (thus considered nonrenewable) fossil fuels form from these decomposed
residues
CAN YOU PLACE NUMBERS 1-9 IN THE DIAGRAM? (text p.256)
If something is missing add it to the diagram.
2.2 NITROGEN CYCLE
-N is needed by living beings to produce protein and DNA, both of which are found in their cells
- Bacteria is needed to change N in the atm. into either ammonia (NH3), ammonium (NH4+),
nitrites (NO2-) or nitrates (NO3-) since N2 cannot not be absorbed directly by most organisms
-Natural factors such as relative humidity, T, and pH affect N cycle
-Human activities such as the use of fertilizers (rich in NH3, NH4+, and NO3-) to boost crop
growth or the discharge of N rich wastewater by industries in waterways greatly affect the soil
and the environment, offsetting the N cycle’s balance
- In a nutshell: atmospheric N enters the earth, undergoes several modifications, & is later
released back into the atm.
Nitrogen Cycle Components
1. Nitrogen fixation
-Specialized bacteria harness N from the atm. and convert it to ammonia (NH3); on contact with
H some of the ammonia is converted to ammonium (NH4+)
2. Nitrification (process by which a nitro grp. is added to an organic cmpd, i.e., a cmpd with O2)
- Some bacteria oxidize ammonium (NH4+) to form nitrites (NO2-)
-Other bacteria oxidize nitrites (NO2-) to form nitrates (NO3-)
3. Nitrogen absorption by plants & animals
- Pl. can absorb ammonium (NH4+) or nitrates (NO3-) from the soil or the water
- Herbivores take in their needed N by eating pl.’s
-Carnivores take in their needed N by eating herbivores or other animals which have N in their
tissues
4. Decomposition of waste
-Specialized bacteria or fungi decompose pl. and an. waste (dead pl.’s & an.’s, feces, urine…) and
convert it to ammonia (NH3) which dissolves to form ammonium (NH4+)
5. Denitrification (opposite of nitrification)
- N returns to the atm. as certain bacteria breakdown nitrates (NO3-) into elemental N
CAN YOU PLACE NUMBERS 1-5 IN THE DIAGRAM? (text p.259)
If something is missing add it to the diagram.
2.3 PHOSPHORUS CYCLE
-P is a building block of DNA; P also enters in the composition of shells, bones, & teeth
-Phosphates (PO43-), a form of P cycles constantly through living beings, the lithosphere, & the
hydrosphere
-Human activities such as the use of phosphate rich fertilizers or residential & industrial wastes
containing phosphate residues from soaps & detergents greatly offset the balance of the natural
cycle
-Runoff from these activities leach into waterways & eventually end up in lakes where cultural
eutrophication occurs, thus depriving lakes of life sustaining O2
Phosphorus Cycle Components
1. Erosion
- P is naturally occurring in rocks
-Wind & rain slowly erodes P from rocks, pieces of which contain phosphates
2. Absorption by living organisms
-Pl.’s will readily absorb phosphates & make it part of their tissues; herbivores & carnivores will
in turn get theirs from eating pl.’s or other animals
3. Decomposition of waste
- Phosphates digested by animals return to the soil in the form of feces & urine
-When specialized bacteria breakdown dead pl.’s & an.’s, phosphates are released to the
environment
4. Proliferation of plankton & sedimentation
- Phosphates released in #3 eventually make their way to the oceans
- Some phosphates will boost plankton growth; plankton are tiny marine organisms which are
either of pl. origin: phytoplankton or of animal origin: zooplankton; plankton is at the base of
marine food chains & it is necessary for their equilibrium
- Some phosphates will sink to the bottom of the ocean where they become part of the sea floor
sediments; over millions of years the mixture will compact forming rock beginning the cycle
once again
(3) BIOMES
- are vast regions of the planet that have their particular flora, fauna, & climate
- 2 types: (1) terrestrial biomes & (2) aquatic biomes
3.1 FACTORS DETERMINING BIOME DISTRIBUTION:
these conditions dictate where beings can live; they limit the distribution of spp.
-Import. factors for terrestrial biomes:
1. Latitude
2. Altitude
3. Precipitation
4. Soil type
5. Am’t of solar ener.
6. Winds
7. Proximity to water
- Import. factors for aquatic biomes:
1. Salinity
2. Turbidity (am’t of suspended particles in water)
3. T
4. Conc.’s of O2 (respiration) & CO2 (photosynthesis)
5. Am’t of solar ener.
6. Nutrients (type, availability …)
7. Depth of water
3.2 TERRESTRIAL BIOMES
- Land biomes; T & precipitation are very import.
-TROPICAL FORESTS
- Situated bet. the Tropics of Cancer (23 ½ °N of Equator) & Capricorn (23 ½ °S of Equator)
- fig. 8.8, p.264
- Mean annual T bet. 20°C & 34°C
- Occupy only 10% of the Earth’s landmass but home to 50 to 80% of the planet’s spp.
- Holds the greatest biodiversity & contributes to climate regulation because of its high biomass
density; tropical forests represent an immeasurable environmental wealth
- threatened due to clearage for farm use & for timber; in 30 yrs millions of hectares
(1 hectare = 2.471 acres or 10,000 m2) have been sacrificed in the name of economic profit,
changing the landscapes & causing even more climate change
-2 types of tropical forests:
(1) Seasonal tropical forest: mainly in Africa; dry & rainy seasons alternate;
(2) Evergreen tropical forest (rainforest): mainly in South America & Asia; rainy season only, up
to 10m of rain yearly
-BOREAL FORESTS
-Make up more than 25% of the world’s forests; forming a
vast green arc under the Arctic Circle
-Made up conifers (esp. black spruce – Xmas tree),
marshland, lakes, & rivers
-Although acidic, shallow, & lacking in nutrients, the soil
sustains an impressive quantity of spp.
-In summer sunlight can be up to 18 hrs long; promoting
growth
-Source of timber; an import. raw material
-Although devastating at times, fire, pests, & disease are
part of this biome’s natural cycle; of greater threat is the
excessive logging, the damages caused by this industry, &
the poorly designed restoration plans
-- The boreal forest spans across Canada, parts of northern
Europe, & Russia
- A huge area of the boreal forest has been destroyed & mismanaged which is unfortunate &
even somewhat baffling since it is considered a renewable resource; other areas have been
cleared for habitation; the map above shows the original extent of the boreal forest 8,000 yrs
ago
- The Sleeping Like a Log campaign, from the Aux Arbres Citoyens conservation group, aims to
inform & desensitize the public & a petition can be signed online
- http://ondortcommeunebuche.citoyenpourlanature.com/en/petition/index.asp
-TEMPERATE FORESTS
-Found in southern Canada, US, Europe & in parts of Asia
-In upper levels this forest consists of a mixture of deciduous (broad leaf; esp. maple, beech, &
birch) & coniferous trees, while in lower levels the forest contains mostly deciduous trees
-Covers the Great Lakes & the St. Lawrence Valley; mean annual T: bet. 8°C & 10°C
-The soil is very rich due to nutrient rich decomposing leaves; soil is able to sustain various spp.
such as moss & grass at ground level, bushes at an intermediate level & final trees at a higher
level; this rich pl. life provides the perfect ecological niche for many animals
-A substantial portion of the temperate forest in Canada was lost to important urban centers
such as Toronto & Montreal the reason being that this forest is found in proximity to major
waterways which were at the root of city development
-Areas of primary forest (a forest that has never been cut) are extremely rare
-ARCTIC TUNDRA
-An arc of green surrounding the North Pole that is sandwiched bet. the Arctic Circle & the
boreal forest; covers the Canadian Far North (Baffin Island, northern Quebec…)
-6% of the world’s landmass; more than 8,000,000 km2
-Grasses, moss, lichen, & dwarfed bushes in the tundra offer enough nutrients & adequate
reproduction sites for many migratory birds (ex. snowy owl – the official bird of Quebec, eiders,
geese…)
-Pl. growth diminished by long cold winters & very short summers that offer 24 hr daylight
-A layer 1m deep thaws by the summer sun where the aver. T is 10°C; lower permafrost layer
does not thaw
-Also home to permanent spp.: arctic fox, lemmings, caribou (picture), arctic hare…
-Extremely fragile to climate change where global warming is happening at twice the rate