Component 1 Flashcards
(22 cards)
Define and describe planetary boundaries.
. A planetary boundary is a threshold value for a global process affected by human development. Crossing these boundaries could result in the causation of abrupt and irreversible environmental changes.
. There are 2 core planetary boundaries - climate change and biodiversity.
. Climate change:
. Caused by the greenhouse effect and global warming, due to combustion of fossil fuels and deforestation, leading to the release of greenhouse gases into the atmosphere.
. Consequences are rising sea levels and low level flooding, melting ice caps and habitat loss, and changes in ocean currents and weather patterns - e.g - extreme rainfall.
. Possible remedies include the reduction in combustion of fossil fuels and deforestation, or use of sustainable biofuels.
. Biodiversity:
. Loss of biodiversity due to overhunting/overfishing, non-contiguous species, and pollution leading to loss of genetic diversity. And habitat destruction e.g - through deforestation, leading to reduced carrying capacity.
. Rapid environmental change caused by human intervention, has led to greater selection pressures and extinction due to species not being able to adapt quickly enough to a changing environment.
. Remedies include monitoring of biodiversity, conservation strategies and education of how to better conserve biodiversity, international cooperation, and preventative legislation to prevent overhunting or mass deforestation.
Define conservation and describe strategies used to conserve biodiversity.
. Conservation is the sensible management of the biosphere and enhancement of local biodiversity.
. Conservation strategies protect existing wild gene pools that provide captive species with adaptive traits. Without these traits, captive species released into the wild will not survive.
. Conservation strategies also protect keystone species e.g - bees, that support entire ecosystems, and plant species that are used in human medicine.
. Strategies include:
. Habitat protection through nature reserves and SSSIs (sites of specific scientific interest), which are protected through legislation.
. International cooperation restricting illegal trade of endangered animal products and reducing overhunting.
. Breeding programmes in zoos and reintroduction of species into their natural environment.
. Sperm banks and seed stores provide a wider gene pool for species and insurance against habitat loss.
. Use of environmental countermeasures to prevent reduction in an area’s biodiversity in the future e.g - re-routing roads to avoid areas of high biodiversity.
Provide examples of agricultural exploitation and strategies to combat this.
. Forestry and mass deforestation:
. Leads to habitat loss and reduced carrying capacity of inhabitant species.
. Also contributes to global warming and climate change through the greenhouse effect - mass deforestation and combustion of trees releases CO2 into the atmosphere, less trees results in less photosynthesis across an area, and CO2 remains in the atmosphere.
. Selective cutting involves only harvesting certain trees each harvest. This protects tree numbers and species’ habitats, also preserving soil nutrients and the microclimate within the soil. However results in less timber being collected each harvest and therefore less economical benefits.
. Coppicing involves cutting a tree to leave a stool, where shoots emerge and form poles. This allows for the tree to regenerate, preserving tree numbers. This also allows for light to reach the forest floor and enhance growth of biodiversity. However, coppiced trees can be considered not aesthetically appealing and poles take time to grow.
. Long rotation times between harvests allow for the regeneration of the soil microclimate after a harvest and the adaptation of inhabitant species. However, this can raise economic issues.
. Methods such as reducing pest intervention on trees and spacing out planted trees to reduce intraspecific competition can ensure a higher quality timber collected and therefore less need to harvest as many trees.
. Crop farming:
. Monoculture involved the dedication of an entire field to growing the most profitable crop. This allows machinery to be used more efficiency, extending profit margins. However, artificial fertilisers and pesticides are required to preserve soil nutrients and prevent pest infestations.
. Artificial fertilisers allow for monoculture by preserving the nutrients that the profitable crop strips from the soil. However, leaching if soluble nitrates into water sources leads to eutrophication and a loss of biodiversity.
. Pesticides allow for monoculture as they reduce the likelihood of specific pests devouring the profitable crop. However, they can also kill off animals, weeds and pollinators supported by the crop, and natural predators of the pests. This reduces biodiversity.
. Removal of hedgerows allows for machinery to be used more efficiently, however this results in species becoming non-contiguous as hedgerows act as wildlife corridors. Therefore groups of a species do not have enough genetically diverse individuals and inbreeding results in the production of an unhealthy population and the eventual extinction of the species.
. Overfishing:
. Overfishing results in loss of marine biodiversity due to the small mesh sizes used in nets causing juvenile fish to be caught before they can sexually mature and breed, and loss of prey for predators, leading to a decline in predator species.
. Exclusion zones prevent fishing in breeding areas during breeding season. This allows for the continuation of marine species and preservation of marine biodiversity. This also conserves predator species. However, this damages the livelihood of fisherman who cannot see a reduction in earnings.
. Removing subsidies provides less encouragement for fisherman to overfish.
. Fishing quotas reduce the volume of fish that fisherman can catch, helping to combat overfishing and preserving marine biodiversity.
. Larger mesh sizes prevent juvenile fish from being caught, maintaining genetic diversity amongst marine populations.
. Fish farming helps to combat overfishing by supplying demand for fish and relieving pressure on fisherman to overfish. Fish farming also produces a lower carbon footprint than traditional agricultural and can combat food demand more sustainably.
. However, fish are packed together leading to rapid spread of disease. These fish may enter the surrounding environment and spread disease to wild fish, or outcompete wild species. This reduces marine biodiversity.
Fish farming can lead to eutrophication of surrounding water due to leaching of soluble nitrates in fish food into the surrounding water.
Describe phases of population growth and factors affecting population growth.
. The lag phase:
. Population growth is slow due to a limited number of individuals to reproduce, individuals are also acclimating to their environment, bacteria and yeast are synthesising new proteins and undergoing cell division at a slower rate.
. The log/exponential phase:
. Population growth is exponential due to a lack of density dependent limiting factors, e.g - Intraspecific competition, and environmental resistance. There is plenty of individuals to reproduce, resulting in birth rate being higher than death rate. Bacteria and yeast undergo cell division at the highest rate due to comfortable access to nutrients.
. The stationary phase:
. The population has reached equilibrium. Birth rate is equal to death rate. Carrying capacity has been reached. Density dependent limiting factors e.g - intraspecific competition, limit population growth.
. The death phase:
. Death rate is greater than birth rate. There is a buildup of toxins die to anaerobic respiration in yeast and bacteria populations.
Define succession and describe stages of succession in an ecosystem.
. Succession is the change in composition and structure of species within an ecosystem over time.
. Each stage of succession is called a sere.
. For succession to progress, Intraspecific competition must be present within all seres, seeds must migrate to form a grassland community, secondary succession must be facilitated by optimum environmental conditions established by previous inhabiting species.
. Primary succession:
. Occurs in a habitat never previously before colonised e.g - bare rock.
. The first sere involves colonisation of a habitat by pioneer species, or extremophile species adapted to survive in extreme conditions e.g - lichens.
. The second sere involves the formation of a grassland community - decomposition of pioneer species allows for the development of soil capable of sustaining low growing herbaceous plants and grasses - seeds are transported to the grassland community through the wind.
. The third sere in succession involves shrubs outcompeting grasses and low growing herbaceous plants for nutrients in the grassland community, their growth preventing sunlight from reaching these plants.
. The final sere is the climax community, dominated by trees but with a variety of plant and animal species. An equilibrium within the community has been reached and species composition remains stable.
. Secondary succession:
. Involves species repopulation of a previously colonised habitat.
. Much quicker than primary succession due to the prescence of a previously established soil microclimate to facilitate growth, presence of roots remaining within the soil for plants to regrow, a previously established seed bank present in the soil for quicker growth of plant species.
Define abundance and distribution of organisms in a habitat and ways of measuring this.
. Abundance:
. The number of of individuals in a species in a given area.
. Quadrat method to measure plant species abundance - measures species density - the mean number of individuals of a species in several quadrats in a given area. Estimates species percentage cover in species with individuals that are difficult to distinguish. Estimates percentage species frequency. Randomise quadrat sampling through generating coordinates randomly on a computer.
. Transect method to measure plant species abundance e.g - a belt transect - measures abundance of a species that lie on a line at measured intervals. Quadrats are positioned alongside the belt at regular intervals, providing readings for density, percentage frequency and area cover.
. Capture-mark-recapture to estimate animal species abundance - individuals are caught, tagged and returned to their environment. Species abundance is measured through the Lincoln index, assuming there is no migration within the population, no births or deaths during the observed time, marked individuals distribute themselves evenly within the population, and marking does not damage survivability.
. Distribution:
. The area in which organisms of a species are found.
. Marking the outermost plants on a map and measuring the area in which they are found.
. Direct observation of animals within an area e.g - nest sites, faecal deposits.
Describe the difference between GPP and NPP.
. GPP, or gross primary production is the rate at which producers produce chemical energy through photosynthesis. On average GPP is 0.2 % of global sunlight energy.
. NPP, or net primary production is GPP minus energy used up by producers during processes such as respiration (lost as heat) or metabolic processes. Therefore NPP represents the energy available to primary consumers on the next trophic level. On average, NPP is 0.1% of global sunlight energy.
Describe how photosynthetic efficiency is calculated and why it is so low.
. Photosynthetic efficiency is a producer’s GPP divided by total light energy falling on the plant, times by 100 to gain a percentage.
. This percentage is so low, e.g - crop plants PE = 7-8%, as sunlight misses the leaves, or if hitting the leaves, can pass through via transmission or not be absorbed by photosynthetic pigments.
Describe how to calculate efficiency of energy transfer between trophic levels and why energy is lost between trophic levels.
. Efficiency of energy transfer = energy incorporated into biomass, divided by energy available in biomass before energy transfer.
. Energy is lost in respiration through heat or metabolic processes e.g - digestive processes - energy lost in excretory products such as urea.
. Not all of the tissue containing biomass e.g - bones, is eaten, or if consumed, not digested so appears in excretory products.
Describe the key processes involved in the carbon cycle.
. Photosynthesis - carbon is removed from the atmospheric store by terrestrial plants and removed from the oceanic store by aquatic plants. This results in formation of biosphere carbon stores e.g- carbohydrates or cellulose.
. Respiration - carbon is released back into the oceanic and atmospheric stores by respiring plants and animals.
. Decomposition - CO2 is released from dead organisms by saprotrophs via saprotrophic extracellular digestion.
. Fossilisation - organisms that have not been fully decomposed are fossilised, creating fossil fuel carbon stores e.g - limestone in marine organisms.
. Combustion of fossil fuels releases carbon back into the atmospheric store.
Describe the greenhouse effect and human contribution towards the enhanced greenhouse effect.
. Long wave solar radiation is reflected from the surface of the earth and trapped in the troposphere by greenhouse gases such as carbon dioxide.
. This contributes to the natural warming of the earth.
. A carbon footprint is the amount of carbon produced by an individual’s actions, a service, or a product in one year.
. Deforestation - less photosynthesis through trees results in the limited removal of carbon dioxide from the atmospheric store. Decomposition of dead wood, after trees have been felled, through saprotrophs, contributes to the release of carbon dioxide into the atmospheric store through saprotrophic respiration.
. An increase in methane production due to increased production of rice crops and the anaerobic conditions present in paddy fields - this leads to anaerobic decomposition of organic matter by methane producing bacteria.
. The increase in cattle ranching to satisfy food demand has also contributed to increased methane emissions as cattle belch methane produced in their stomachs.
. A higher volume of rotting material in landfill sites has also contributed to increased methane emissions.
. Combustion of fossil fuels - CO2 is released back into the atmospheric store during combustion of fossil fuel carbon stores.
. Production of CFCs - CFCs are a more active greenhouse gas than CO2. Produced through aerosols and coolants in freezers and refrigerators.
Describe the processes involved in the nitrogen cycle.
. The nitrogen cycle is the flow of, organic and inorganic, nitrogen containing compounds, within abiotic and biotic components of an ecosystem.
. There are 4 key processes involved: nitrogen fixation, ammonification, and nitrification or denitrification.
. Nitrogen fixation:
. Is where nitrogen molecules in the atmosphere are combined with oxygen or hydrogen molecules.
. This occurs through lightning fixation, industrial fixation, or biological fixation:
. Lightning fixation is where lightning breaks nitrogen molecules so that they can combine with oxygen in the atmosphere and form nitrogen oxides.
Nitrogen oxides dissolve in rain and fall on the soil as nitrogen ions.
. Industrial fixation occurs through the Haber process, where atmospheric nitrogen is combined with hydrogen under extreme pressure and temperatures, to form ammonia or ammonium ions.
. Biological fixation occurs through nitrogen fixing bacteria on the soil. Another example being Azotobacter, which live freely in the soil and combine nitrogen gas with hydrogen gas to form ammonium ions.
Rhizobium, another nitrogen fixing bacteria, live under anaerobic conditions in root nodules of legumes. In these anaerobic conditions, they credited nitrogen into ammonium ions in a reaction catalysed by the nitrogenase enzyme.
. Ammonification:
. Ammonification involves the decomposition and breakdown of amino acids in dead animals, urine, and faeces by saprotrophs, which convert the amino acids into ammonium ions. This process is called putrefaction.
. Nitrification:
. In an oxidation reaction, aerobic nitrifying bacteria oxidise ammonium and then nitrite ions to form nitrate ions.
Nitrosomonas oxidises ammonium to form nitrite ions, and Nitrobacter oxidises nitrate ions to form nitrate ions.
Nitrate ions can be absorbed by plants through their roots via facilitated diffusion or active transport, and assimilated into organic nitrogen containing compounds e.g- amino acids.
. Denitrification:
. Denitrification is the reduction of nitrate ions back into nitrogen gas by anaerobic bacteria e.g- pseudomonas, who inhabit anaerobic environments such as waterlogged soil.
How can farmers produce and sustain aerobic conditions within their soil ?
. Ploughing - encourages soil turnover, increasing oxygen saturation and growth of nitrifying aerobic bacteria. Discourages growth of anaerobic denitrifying bacteria.
. Drainage systems - reduce water logging and risk of soil conditions becoming anaerobic.
. Growing leguminous plants containing Rhizobium in root nodules to increase nitrogen content of soil.
Describe the adaptations of chloroplasts and angiosperm leaves for photosynthesis.
. Chloroplasts contain photo systems within the thylakoid membranes - photo systems are clusters of photosynthetic antenna pigments - beta carotene, chlorophyll b and xanthophyll, around the primary pigment - chlorophyll a, in the reaction centre.
Photons of light are transferred through the antenna complex before reaching the reaction centre, where they are absorbed by chlorophyll a, and used to power light dependent reactions involved in photosynthesis.
. Chloroplasts contain many different photosynthetic pigments within the thylakoids to absorb a range of different wavelengths of light and reduce chances of reflection.
. Leaves project a large surface area to absorb as many wavelengths of light as possible.
. Leaves are thin and contain air spaces between layers to allow for efficient diffusion of carbon dioxide into the cells.
. The cuticle and epidermis are transparent to allow for light to penetrate the leaf and be absorbed by photosynthetic pigments within the thylakoids.
Describe the light dependent stage of photosynthesis.
. Light dependent reactions occur within the thylakoid membranes and thylakoid cavity.
. They require light energy and water.
. Aim to convert solar energy into chemical energy - ATP and NADPH, for synthesis of sugars using CO2 in the Calvin cycle.
. Using solar energy , ADP is phosphorylated in cyclic or non-cyclic photophosphorylation to produce ATP.
. Cyclic photophosphorylation/chemiosmosis:
. Photons of light are absorbed by photo system 1 and pass through the antenna complex to chlorophyll a in the reaction centre.
. Chlorophyll a is excited and releases high energy electrons - chlorophyll a is oxidised.
. Electrons released pass down the electron transport chain through electron acceptors, before returning to PS1 to be accepted by chlorophyll a, which becomes reduced.
. This produces sufficient energy to synthesise ATP through chemiosmosis.
. Non-cyclic photophosphorylation:
. Photons of light are absorbed by PS1 and PS2.
. Light energy passes through the antenna complex before being absorbed by chlorophyll a in the reaction centre.
. Chlorophyll a becomes excited and releases high energy electrons - chlorophyll a is oxidised.
. High energy electrons pass through the electron transport chain and are accepted by electron acceptors.
. Energy lost from electrons powers proton pumps in the thylakoid membranes and which actively pump H ions across the thylakoid membrane into the thylakoid space.
. H ions accumulate in the thylakoid space, creating an electrochemical gradient for them to diffuse down, via facilitated diffusion, through ATP synthase and into the stroma.
. ATP synthase catalyses the phosphorylation of ADP to synthesise ATP.
. This is called chemiosmosis.
. Lost electrons from PS2 are replaced through photolysis of water, which produces H ions, oxygen, and high energy electrons.
. Hydrogen ions and electrons are used reduce NADP, whilst O2 diffuses out of the plant via stomata.
Describe the light independent stage of photosynthesis.
. Otherwise known as the Calvin Cycle.
. Occurs within the stroma.
. Uses NADPH and ATP produced in the light dependent stage, as well as CO2 that diffuses into the plant via stomata, to synthesise glucose.
. CO2 is fixated when it combines with the 5C compound ribulose bisphosphate to form an unstable 6 carbon molecule. This reaction is catalysed by the RUBISCO enzyme.
. The unstable 6 carbon molecule dissociates into two 3C glycerate-3-phosphate molecules.
. Using energy produced through hydrolysis of ATP and a H ion and electrons donated by NADPH, the 2 glucerate-3-phosphate molecules are reduced to form 2 triose phosphate molecules.
. For every 6 TP molecules produced, 5 are used to regenerate ribulose bisphosphate and the other 1 is used to synthesise glucose or other organic molecules such as carbohydrates, amino acids and lipids.
Outline different plant mineral requirements and the consequences of insufficient mineral quantities.
. Magnesium - required for activation of ATP synthase and manufacture of chlorophyll. Deficits result in chlorosis (yellowing of leaves).
. Nitrogen - required for synthesis of proteins. Deficits results in hindered cell division and therefore growth.
Describe processes involved in anaerobic respiration.
. Glycolysis:
. Occurs in the cytoplasm.
. Glucose is reduced to a form where it is able to enter the mitochondria.
. Enzymes required to reduce glucose aren’t present in the mitochondria.
. Glucose (6C) is phosphorylated through substrate level phosphorylation - used phosphate groups from two ATP molecules, to produce hexose bisphosphate (6C).
. Hexose bisphosphate is more reactive, lowering activation energy required in enzyme catalysed reactions, but also polar, so less likely to diffuse out of the cell.
. Hexose bisphosphate is unstable and dissociates into two 3C triose phosphate molecules.
. The 2 triose phosphate molecules are dehydrogenated by the dehydrogenase coenzyme, which passes the H ions to the hydrogen carrier NAD, which becomes reduced. The two triose phosphate molecules become oxidised.
. The dehydrogenation of the 2 triose phosphate molecules produces 2 pyruvate molecules.
. This also releases enough energy to synthesise 4 ATP molecules through phosphorylation of 4 ADP molecules.
. Per glucose molecule, glycolysis produces 2 ATP molecules, with 2 being used, 2 reduced NAD molecules, and 2 pyruvate molecules.
. Fermentation:
. The aim of fermentation is to continue NAD production, to allow for ATP production to continue in anaerobic conditions through glycolysis, until oxygen becomes available.
. Lactate fermentation:
. Two NADH molecules are oxidised, providing H ions to reduce pyruvate to form lactate.
. Lactate fermentation produces 2 NAD molecules for glycolysis to continue, and lactate.
. Alcohol fermentation:
. Occurs in yeast cells.
. 2 CO2 molecules are removed from 2 pyruvate molecules via the decarboxylase coenzyme to form 2 ethanal molecules.
. 2 NADH molecules donate H ions to reduce the 2 ethanal molecules and produce 2 ethanol molecules.
. The NADH molecules become oxidised.
. Alcohol fermentation forms 2 NAD molecules for ATP synthesis in glycolysis to continue, 2 ethanol, and 2 CO2.
Describe processes involved in aerobic respiration.
. Glycolysis.
. The link reaction:
. Pyruvate (3C) enters the mitochondrial matrix.
. Pyruvate is oxidised by the dehydrogenase co-enzyme which donates the H ion to NAD, which becomes reduced.
. Pyruvate also undergoes decarboxylation by decarboxylase.
. The product is acetate (2C) which joins to co-enzyme A, forming acetyl coA.
. The link reaction produces 2 NADH molecules, 2 CO2 molecules, and 2 acetyl coA molecules per glucose molecule.
. The Krebs cycle:
. Also occurs in the mitochondrial matrix.
. Acetate is offloaded from acetyl coA and combines with 4C oxaloacetate acid to form citric acid (6C).
. Citric acid undergoes decarboxylation via decarboxylase enzyme and dehydrogenation via dehydrogenase enzyme, becoming oxidised, with the H ion passing to the H carrier NAD, which becomes reduced.
. The products are a 5C intermediate and reduced NAD.
. The 5C intermediate is decarboxylated via the decarboxylase co-enzyme and dehydrogenated via the dehydrogenase co-enzyme. It becomes oxidised and the H passes to another molecule of NAD which becomes reduced.
. This produces a 4C intermediate, and reduced NAD.
. The 4C intermediate is converted into another 4C intermediate.
. Overall, this releases enough energy to phosphorylate 1 molecule of ADP, forming 1 molecule of ATP via substrate level phosphorylation.
. The second 4C intermediate is oxidised and the H ion is donated to the H carrier FAD which becomes reduced.
. This forms a 3rd 4C intermediate and reduced FAD.
. The 3rd 4C intermediate is further dehydrogenated to regenerate oxaloacetate (4C). This occurs via the coenzyme dehydrogenase, the H ion being donated to NAD which becomes reduced.
. There are 2 turns of the Krebs cycle per molecule of glucose, as acetyl coA is formed from 1 molecule of pyruvate.
. Each glucose molecule results in the production of 6 NADH molecules, 2 FADH molecules, 2 ATP via substrate level phosphorylation, and 4 CO2 through the Krebs cycle.
. The electron transport chain:
. Occurs in the inner mitochondrial membrane.
. Reduced NAD and reduced FAD are dehydrogenated via dehydrogenase enzyme and become oxidised.
. The H ions released are split into high energy electrons.
. The electrons pass down the electron transport chain and are accepted by electron acceptors within the inner mitochondrial membrane.
. This produces energy used to power proton pumps, which actively pump H ions into the inter membrane space, creating an electrochemical gradient for them to diffuse down, through ATP synthase in the inner mitochondrial membrane, and into the matrix.
. ATP is produced through phosphorylation of ADP via chemiosmosis.
. Electrons are finally donated to oxygen, the final electron acceptor. Oxygen also accepts H ions from the mitochondrial matrix, forming water.
. After the electron transport chain, 38 molecules of ATP are produced per molecule of glucose - 4 from substrate level phosphorylation and 34 from oxidative phosphorylation.
Compare staining of gram positive and gram negative bacteria and explain why this difference occurs.
. Gram positive - Purple - the thick peptidoglycan cell wall holds onto the crystal violet stain which is not washed out by ethanol.
. Gram negative - Pink - crystal violet is removed when washed with ethanol along with the outer lipopolysaccharide layer, so a counter stain (safranin) is used which is held onto by the now exposed peptidoglycan cell wall.
Describe the difference between obligate aerobes, facultative anaerobes, and obligate anaerobes.
. Obligate aerobes are bacterial cells that grow and divide in aerobic conditions.
. Obligate anaerobes grow and divide in anaerobic conditions.
. Facultative anaerobes can grow and divide in both aerobic and anaerobic conditions but grow best in aerobic conditions.
Describe the procedures in which bacteria are cultured.
. The agar or nutrient broth must contain a source of carbon, nitrogen, water, vitamins, and mineral salts.
. Optionally, components such as salt blood or starch can be added to produce a selective medium to culture different bacterial types.
. Oxygen can be added to culture obligate aerobes and facultative anaerobes only.
. Antibiotics can be added to grow only resistant bacteria.
. Bacteria must be cultured below 35 degrees celsius (25 in school labs) over a 24 hour period to prevent growth of human pathogens. Petri dishes are sealed with tape also to prevent this.
. Aseptic technique must also be used to prevent spread of bacteria outside of the lab.
. This includes hand washing before and after culturing, sterilising work benches and equipment e.g - under a Bunsen flame, creating a convection current using a roaring blue flame, necks of agar bottles and cultures should be flamed and the lid of the culture should be held off the bench by the little finger.
. A serial dilution is then prepared - 9cm cubed of water is placed in 10 sterile tubes and the culture is added systematically. A gar plates of the dilutions are prepared and bacteria are cultured.
. A viable count follows.
. Viable counts include only living bacterial cells, the number of colonies is counted on the most appropriate dilution Petri dish (one without clumping) and the dilution factor is taken into account to give an estimate of number of viable bacterial cells in the original sample.
. Total counts can be gained through using a haemocytometer, and include living and dead bacterial cells.
