Key POINTS The Biosphere WHAT IS THE BIOSPHERE? - The living layer which includes all organisms & their habitat, that is: lithosphere + hydrosphere + atmosphere (solid layer: (water layer: ice, glaciers, (air layer) sediments & soil) seawater, freshwater) (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) • 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 • 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: - Import. factors for aquatic biomes: • 1. Latitude 1. Salinity • 2. Altitude 2. Turbidity (am’t of suspended particles in water) • 3. Precipitation 3. T • 4. Soil type 4. Conc.’s of O2 (respiration) & CO2 (photosynthesis) • 5. Am’t of solar ener. 5. Am’t of solar ener. • 6. Winds 6. Nutrients (type, availability …) • 7. Proximity to water 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: • 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 ArbresCitoyens 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