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TOPIC 4: Ecology, Explain how natural selection can lead to speciation.,…
TOPIC 4: Ecology
4.4 Climate change
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Other greenhouse gases are methane /produced by methanogenesis and nitrogen oxides. these have less impact on the warming effect because they are less abundant.
o2 and n2 are not greenhouse gases because they do not absorb long wave radiation.
the impact of a gas depends on its ability to absrob long wave radiation as well as its concentration in the atmopshre.
ch4 has a larger weaming effect but has lower atmospheric concentratinos.
the warmed surface of the Earth absorbs short-wave energy from the sun and then re-emits it, but at much longer wavelengths. most re-emitted energy is infrared and has long wavelengths.
- greenhouse gases retain and absorb long wave radiation to heat the atmopshre and keep the erath warm.
Longer wave radiation is absorbed by greenhouse gases that retain the heat in the atmosphere.
most short wave radiation is absorbed by the atmopshere before reaching the earths surface.
most solar radiation is absrobed by ozone (uv rays), the rest reaches the earths surface and converted to heat. (70%)
long wave radiation is re emitted by the surface of the earth and absorbed by greenhouse gases. the energy is retained to keep the earth warm.
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There is a correlation between rising atmospheric concentrations of carbon dioxide since the start of the industrial revolution 200 years ago and average global temperatures.
the industrial revolution increased the amount of fossil fuels being burned. the burning of fossil fuels releases co2 as a by product which increased co2 concentrations.
- trends are revealed when comapring co2 concentrations and global temperatures
- strong position correlation between the burningn of fosill fuels since the industrial revoliution and co2 conc.
- most co2 is absorbed by carbon sinks and the rest remains in atmosphere.
correlation does not imply causation.
Recent increases in atmospheric carbon dioxide are largely due to increases in the combustion of fossilized organic matter.
since the industrial revolution increasing number of coals and fossil fuels are being burned as a source of heat, this has increased co2 emissions. increased relaiance on co2 emissions has increased co2 concentrations, leading to higher global temperatures.
threats to coral reefs from increasing concentrations of dissolved co2.
Ocean acidification refers to a reduction in the pH of the ocean over a long period of time, caused primarily by uptake of carbon dioxide (CO2) from the atmosphere.
increasing co2 emissions are having effects on oceans. since the start off the industrial revilutiuon, co2 levels have icnreased in ocens. co2 reacts with water to form carbonic acid, this decreases the pH of oceans.
ocean acidiciation will become more severe as co2 concentrations increase.
marine animals like reef-building corals deposit calcium carbonate in their skeletons and must absorb carbonate ions from seawater.
carbonate ion concentrations are low becauyse they are not very soluble, increasing oceanic temperatureds is decreasing their solubiilut.
h+ ions are reacting with co3 2- (carbonate ions), threatening the life of reef building corals (mollsucs).
Evaluating claims that human activities are not causing climate change: evidence
NO SCIENTIFIC CONCESUS = 98% climate experts agree that humans are causing climate change.
GLOABL TEMP ARE DECREASING = global temps are on the rise
ANTANRTICA IS GAINING ICE = it is loosing ice and a fast rate
rising co2 levels also icnreases h20 vapor, increasing the global warming effect
global warming is making extreme weather events more frequent.
4.2 Energy flow
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light energy is converted into chemical energy in carbon compounds by photosynthesis. producers absorb sunlight using chlorphyll and other photosynthetic pigments. this energy is used to synthesises organic compounds. producers can release energy from their carbon compounds by cell respiration. energy released is lost to the environment as waste heat
Chemical energy in carbon compounds flows through food chains by means of feeding.
A food chain shows the linear feeding relationships between species in a community
Trophic levels are the position an organism occupies within a feeding sequence.
producers always occupy the first trophic level in a feeding sequence. primary consumers feed on producers.
consumers obtain energy from the carbon compounds in the irganisms in which they feed. the arrows in a food chain indicate the direction of energy flow.
Energy released from carbon compounds by respiration is used in living organisms and converted to heat.
living organisms need energy for cell activiy such as DNA synthesis in replication. ATP supplies energy for these activities. All cells can produce ATP from cell respiration. Not all energy in organic compounds is transferred via heterotrophic feeding. Some chemical energy is lost by being excreted or remaining unconsumed.
in cell respiuration, carbon compounds are oxidised. oxidation reactions are exothermic and therefore the energy is released to the environment.
energy transformations are never 100% efficient, some of the energy from respiration and oxiadtion are converted to heat and not ATP. energy from ATP may reside for a long time, but when the molecules are digested the energy is released as heat.
Living organisms cannot convert heat to other forms of energy. organisms can convert light, electrical, chemical and kinetic energu into heat energy. but they cannot convert heat energy into any other form of energy.
Heat is lost from ecosystems. : Heat from cell respiration makes living organisms warmer. Heat passes from hotter bodies to cooler bodies, so heat produced by organisms is eventually lost to the abiotic environment.
Energy losses between trophic levels restricts the length of food chain and the biomass at higher trophic levels.
- biomass is the total mass of a group of organisms, composed of all organic compounds.
- most of the energy absorbed by an organism is used in respiration, released as heat,
excreted as faeces or unconsumed.
- thus not all parts of food ingested in a food chain are digested and absorbed.
- some materiall cannot be digested and is excreted as faces. energy in facees does not pass through the food chain.
- uneaten material stores enegry that is
because of these energy losses only a small portion of energy in the biomass of organisms in one trophic level will be passed to the next trophic level.
- as the losses occur at each stage in a food chain there is less energy available to each succesgive trophic level.
- after a few stages the amount of energy avilable would not be enough to support another trophic level, restricting the length of trophic levels.
energy flow (6)
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producers eaten by primary consumers, these by secondary consumers, (these by tertiary consumers)/energy moves up trophic levels;
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Pyramids of energy. A pyramid of energy is a graphical representation of the amount of energy at each trophic level of a food chain. They are never inverted because energy is lost upong transfer. energy transofrmtions are never 100% efficient, only 10% of energy is trnasfered along the food chain.
4.1 Species, Communities and Ecosystems
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Species have either an autotrophic or heterotrophic method of nutrition (a few species have both methods).
Autotrophs obtain inorganic nutrients from the abiotic environment and synthesise their own organic molecules. energy for this process is derived from the sun by photosynthesis.
AUTOTROPHS ARE PRODUCERS AND WILL HAVE THE FIRST TROPHIC LEVEL IN A FOOD CHAIN.
- most plants and algae are autotrophic, they make their organic compounds from co2 and their environment.
- autotrophs that cannot photosyntehsise may grow on other plants and cause harm, they are said to be parasitic.
Consumers are heterotrophs that feed on living organisms by ingestion.
Heterotrophs obtain organic molecules by feeding on other organisms.
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consumers feed off other organisms: (1) still alive (2) have been dead for a short time. Consumers take in undigested material from other organisms. they digest it and absorb the products of digesiton. Consumers are divided into trophic levels according to their method of nutrition.
Detritivores are heterotrophs that obtain organic nutrients from detritus by internal digestion.
dead matter from organisms is used as a source of nutrition by heterotrophs (leaves)
Saprotrophs are heterotrophs that obtain organic nutrients from dead organisms by external digestion.
saprotrophs release digestive enzymes and then absorb the external products of digestion.
saprotrophs release digestive enzymes and then absorb the external products of digestion. they are decomposers because they break down carbon compounds in dead organic matter and release elements into the ecosystem for use.
A community is a group of populations living together and interacting with each other within the same area. species are dependent on their relationship with other spcies for long term survival. groups of populations live together because species cannot live in isolation.
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living organisms depend on their abiotic environment. their environment exerts a powerful influence over the organisms.
Ecosystems have the potential to be sustainable over long periods of time.
Something is sustainable if it can continue indefinitely (human use of fossil fuel is unsustainable)
Natural ecosystems are sustainable if they have (1) nutrient availability (2) detoxification of waste products (3) energy availabilities.
The supply of inorganic nutrients is maintained by nutrient recycling. = elements that living organisms need are constantly recycled.
chemical elements can be recycled. organisms absorb the elemnts that they require as inorganic nutrients from the abiotic environemt, they use them and return them to the environment.
autotrophs and hetertrophs obtain inorganic nutrients from the abiotic environment.
1) autotrophs obtain inorganic nutrients from the air, soil/water (abiotic environment) and convert them to organic products.
2) heterotrophs feed off the organic compounds produced by autotrophs
3) when organisms die, saprotrophs decompose the remains and free inorganic material into the soil.
4) the return of inorganic material to the soil ensures the continual supply of raw materials for autotrophs.
Setting up sealed mesocosms to try and establish sustainability.
Mesocosms are enclosed environments that allow a small part of a natural environment it be observed under controlled condtions.
H0 = no statisical relationship H1 = there is an association
Quadrants are square sample areas. Quadrant sampling involves placing a quadrant frame at random positions in a habitat and recording the number of organisms present at each time.
A statistical test called the chi-squared test determines whether there is a significant difference between the observed and expected results in an experiment
if p < 0.05, we can say that there is a statistically insignificant relationship between the two variables. u need to be able to interpret the results.
4.3 Carbon cycling
Autotrophs convert carbon dioxide into carbohydrates and other carbon compounds. Autotrophs reduce co2 concentration in the atmosphere. co2 concentration will be low in photosynthetic organism and higher in the atmosphere. This establishes a concentration gradient, ensuring that co2 passively diffuses into the autotrophic organism as required.
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Carbon dioxide diffuses from the atmosphere or water into autotrophs. Carbon dioxide is produced by respiration and diffuses out of organisms into water or the atmosphere.
cell respuration produces co2 as a by product. all these organisms undergo respiration and therefore release co2.
- if theres more net photosynthesis occurring in the biosphere, co2 levels will drop.
- if there's more respiration than photosynthesis, co2 levels will rise.
Methane is produced from organic matter in anaerobic conditions by methanogenic archaeans and some diffuses into the atmosphere or accumlates underground.
methanogens are archaen microorganisms that produce ch4 as a by product of anaerobic respiration. archanes produces ch4 from co2 and hydrogen. co2+h2--> ch4+h20
some ch4 is diffused into the atmosphere or accumulates underground.
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ch4 is oxidised to co2 and water in the atmosphere methane is naturally oxidised in the atmopshere so it is not an abundant atmospheric gas, high amounts are produced by methanogens but concentrations are low
Peat forms when organic matter is not fully decomposed because of acidic and/or anaerobic conditions in waterlogged soils.
Peat is formed from dead plant material
b. formed in waterlogged sites/bogs/mires/swamps
c. where bacteria/fungi/saprotrophs are not active.
d. organic matter not fully decomposed
e. «occurs» in acidic conditions
f. «occurs» in anaerobic conditions
«very» slow process/takes a long time
ANAEROBIC CONDTIONS NOT RESPIRATION
in many soils saprotrophic bacteria will decompose dead organisms and return nutrients to the soil for cycling. decomposition requries oxygen.
- waterlogged soils lack oxygenated air spaces within the soil and therefore posses anaerobic conditions.
- anaerobic condtions results in acetate, saprotophs cannot decompose in acidic conditions, preventing decomposition.
- carbon rich molecules remain in the soil as peat. When deposits of peat are compressed under sediments, the heat and pressure forces out impurities and remove moisture.
- The remaining material has a high carbon concentration and develops into coal.
Peat is formed when partially decomposed organic matter is compressed in anaerobic waterlogged soils to form a brown soil like carbon rich matter.
Carbon dioxide is produced by combustion of biomass and fossilized organic matter.
When organic compounds are heated in the presence of o2 they undergo a combustion reaction that is exothermic. complete combustion of carbon compounds releases co2 and water into the atmosphere. crude oil and coal are sources of combustion which are burned as fuels.
Partially decomposed organic matter from past geological eras was converted either into coal or into oil and gas that accumulate in porous rocks.
carbon compounds are very stable and can remain unchanged for millions of years.
- deposist of carbon from past geological eras are the result incomplete decomposition of organic matter found in sediments that became rock.
- coal is formed when deposits of peat are buried under other sediments and compressed.
- oil and natural gas are formed at the bottom of oceans and lakes under anaerobic conditions, from incomplete decomposition. chemical changes occurs to peat taht propduces liquid or gaseous carbion compound (natural gas/coal/crude oil).
Animals such as reef-building corals and Mollusca have hard parts that are composed of calcium carbonate and can become fossilized in limestone.
Mollusc shells and hard corals contain caco3. when the organisms die their soft parts decompose. in acidic conditions the caco3 dissolves, but in basic condition it forms desposits on the sea bed/precipitates in water.
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carbon fluxes describe the rate of exchange of carbon between carbon sinks and reserves. mesocosms are used to estimate carbon fluxes.
co2 concentrations affect photosynthetic rates and the pH of seawater/global temperatures too and the sea level.
the carbon cycle is a cycle whereby carbon is exchanged between different spheres of the earth (biosphere/hydrosphere/lithosphere) carbon is exchanged in a variety of forms, such as gases, organic material and oceanic carbonates.
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plants/producers and animals/consumers linked to carbon in air/CO2 with arrow labeled (cell) respiration;
plants/producers and animals/consumers linked to decomposers/bacteria/fungi with arrow labeled death;
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decomposers/bacteria/fungi linked to fossil fuels/coal/oil/natural gas with arrow labeled (partial) decomposition;
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A carbon sink is a part of the carbon cycle that takes up and stores carbon, e.g.
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Outline the roles bacteria play in the carbon cycle:
a. decomposition of dead organic material «by saprotrophic bacteria»
b. «decomposition» leads to CO2 formation/regeneration due to respiration
c. «saprotrophic bacteria only» partially decompose dead organic matter in acidic/anaerobic conditions in waterlogged soil
d. results in peat formation in bogs/swamps
e. photosynthetic bacteria/cyanobacteria fix CO2 in photosynthesis
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