Miya Ntentabunga-
Suggest how this experiment shows that pigeon droppings represent a realized ecological niche for C. neoformans and a fundamental (but not a realized) niche for C. gattii.
the realised niche is the actual while the fundamental niche is all of the potential
shared fundamental niche shown by equal reproduction on control
C. neoformans reproduces on PD indicating a realised ecological niche
competitive exclusion decreases realized niche of C. gattii
C. gattii reproduces poorly on PD representing a fundamental niche
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State the type of interaction that occurs between Zooxanthellae and reef-building corals.
symbiosis
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State the trophic level of Zooxanthellae.
producers
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When coral is bleached, certain organisms become more common in the ecosystem such as the cnidarian Gorgonia, the echinoderm Diadema, other algae and certain sponges. State the term that is used for organisms whose presence provides evidence of the existence of a particular environmental condition.
indicator species
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A coat of algae builds up on coral reefs as a consequence of eutrophication. Explain the relationship between eutrophication and algal growth.
eutrophication is nutrient enrichment of a body of water
eg: nitrates
nutrients serve as fertiliser for the algae promoting growth
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Explain how an excessive growth of algae on coral reefs can be controlled by top-down factors
top-down factors refer to predation/herbivory/trophic level above another onewhich limit/control population growth
eg: parrotfish
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biotic factors, other than wolf predation or culling, that could affect the elk population
A. relative rates of natality;
b. disease/lack of food;
c. competition for the same resources;
d. immigration/emigration/migration;
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Outline a method that could have been used in this study to measure the numbers of sea urchins per 0.25 m2.
a. with quadrats (of 0.5 m side / 0.25m2);
b. (quadrats) position determined at fixed distance by transects
c. random sampling / capture-recapture;
d. average number calculated;
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Sea otters are considered keystone species in this environment. Suggest how the presence of sea otters could affect the algae population.
a. sea otters (feeding on sea urchins) limit sea urchin population;
b. the largest sea urchins are eaten;
c. shown by low biomass/small size (of sea urchins);
d. fewer/smaller sea urchins allow for increase in algae population;
e. sea otters have a top down effect;
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Sea urchins are destroying the giant kelp alga (Macrocystis pyrifera) marine forests of South East Australia. Suggest a reason that sea urchins might be an invasive species in this environment.
the sea urchins’ limiting factors in their original habitat are missing
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Define fundamental niche.
the potential/full range of conditions under which an organism can live
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Outline a reason for organisms seldom occupying their entire fundamental niche
competition for resources/named resource
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Describe the relationship between Zooxanthellae and reef-building coral species.
a. endosymbiotic/mutualistic relationship
b. zooxanthellae/photosynthetic algae/dinoflagellates live in coral tissues
c. coral provides protection for algae/dinoflagellates
d. algae/dinoflagellates provide minerals/products of photosynthesis/oxygen/sugars to coral
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Distinguish between fundamental niche and realized niche.
fundamental niche is all potential conditions a species could live in whereas realized niche is actual conditions under which the species live
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Outline the characteristics of keystone species in an ecosystem.
a. keystone species has a strong/disproportionate effect on a community/food web/ecosystem
b. absence of keystone species would completely alter the ecosystem
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Outline one example of mutualism.
a. oxpecker (bird) and zebra
b. oxpeckers/bird on zebras eat parasites getting food while zebra get pest control
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Explain how nutrients can have a positive or negative bottom-up effect on seagrass.
a. the positive bottom up effect is due to availability of nutrients
b. nutrients increase abundance/plant growth rates
c. the negative bottom-up effect as excess of nutrients causes a bloom in algae growth/eutrophication/competition
d. limited nutrients have negative effect on seagrass growth
e. excess algae cause seagrass to die/decompose/replenish nutrients
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State one advantage of this in situ conservation method.
organisms remain in their own habitat
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Suggest one reason for leaving natural corridors between different natural reserves.
increases edge effect and thus biodiversity
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State what a high value of Simpson’s reciprocal index of diversity suggests about an ecosystem.
stable/balanced ecosystem
ecosystem not under stress
absence of changes
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Explain how the shape and size of a protected area may influence its success in protecting the organisms and ecosystems within it.
a. size and shape determine the length of perimeter/edge
b. perimeter determines importance of edge effect
c. greater edge effect results in increased biodiversity
d. large areas can conserve a greater number of habitats
e. large areas make it easier for poachers to go undetected.
f. corridors promote movement between habitats
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Feed conversion ratio (FCR) is the mass of animal feed in kilograms required for farmed animals to produce one kilogram of edible mass. For example, the FCR for salmon is 1.2 and for chicken is 2.2. Deduce the implication of these ratios for sustainability.
a. higher FCR implies less sustainability
b. salmon based diet is more sustainable/chicken is less
c. salmon diet would have lower energy losses/chicken diet higher energy losses
d. salmon diet will produce less waste/chicken more
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Evaluate the use of food webs to represent ecological communities.
a. food webs summarise all possible food chains in the community
b. realistic representation
c. some communities/ecosystems are too complex to represent
d. only shows qualitative information/not quantitative data
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Distinguish between mutualism and parasitism, providing another example of mutualism and another example of parasitism.
a. in parasitism only one organism benefits whereas in mutualism both benefit
b. eg parasitic: human tapeworms
mutualism: bacteria in human digestive tract
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Define indicator species.
organism used to assess a specific environmental condition
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Indicator species may be affected by biomagnification. Discuss biomagnification using a named example of a pollutant
a. eg: mercury
b. substance accumulates in fat tissue/not excreted when consumed
c. contaminated organisms consumed in large quantities by higher level consumers
d. pollutant becomes more concentrated at each higher trophic level / through the food chain
e. some pollutants are more likely to be biomagnified accumulate in fat tissue
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Determine whether islands are open or closed ecosystems.
closed because islands do not exchange matter/nutrients with surroundings
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Distinguish between tropical rainforest and taiga in terms of nutrient stores, nutrient flows and climate. Gersmehl diagrams can be used to support your answer.
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A coat of algae builds up on coral reefs as a consequence of eutrophication. Explain the relationship between eutrophication and algal growth.
a. eutrophication is nutrient enrichment of a body of water
b. example of nutrients eg: nitrates
c. nutrients serve as fertiliser for the algae promoting growth
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Construct a Gersmehl diagram on the outline provided, to show flows of nutrients between stores in tropical rainforests.
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State the property that makes the mesocosms open ecosystems.
there is exchange of matter/energy
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Assuming that the populations of bacteria are under bottom-up control, identify the mesocosms in which the bacterial populations will be highest.
soil and no fish «mesocosm» AND soil and fish «mesocosm»
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Outline top-down effects on the bacteria in the four mesocosms.
zooplankton feed on bacteria reducing their numbers
fish feed on zooplankton therefore increasing bacterial population
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Suggest advantages of undertaking this experiment in the sea rather than in the laboratory
conditions closer to levels experienced naturally by the organism
natural variation of abiotic variables
more natural behaviour/interactions
not harm organisms by removing them from natural habitat
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State one abiotic factor that will determine the type of ecosystem in a succession.
temperature
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Predict the process of succession that takes place on exposed bare ground as the glacier retreats.
a. (bare ground) colonized by microorganisms/pioneer species
b. thin soil forms from rock fragments / decomposing organisms
c. soil retains water from melting permafrost/ice
d. grasses/small plants/herbaceous plants/moss grow
e. (larger plants) create habitat for animals
f. weather/climate may limit plant size/biodiversity
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Compare and contrast food chains and food webs.
Similarities:
a. in both food webs and chains organisms are arranged by trophic levels/feeding positions
b. both represent the transfer of food/energy in an ecosystem
c. both include producers and consumers
Differences:
d. one species could occupy different trophic levels in a food web but not in a food chain / converse
e. food chain represents one possible feeding option for each organism but food web represents more possible feeding relationships/trophic levels
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Outline what is represented by the arrows in the Gersmehl diagram.
nutrient flow
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Explain how the amount of litter in a tropical rainforest would differ from the taiga’s and how this would be represented in a Gersmehl diagram.
the circle would be relatively smaller
warmer weather favours the decomposition of litter
more rainfall favours the decomposition of litter
greater number of saprophytes
nutrients would be stored in biomass/biomass circle would be larger
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Predict one example of macroplastic pollution that is likely to be found
plastic bottles
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State two possible effects on organisms of microplastic pollution.
a. ingestion can reduce feeding
b. microplastics absorb toxins from water
d. biomagnification
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Outline the effect of wind on the distribution of plastic pollution in this lake.
a. microplastic density higher along the north»western shore than the eastern shore
b. wind causes currents which moves the plastics
c. macroplastic pollution less affected by wind than microplastic pollution
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Suggest changes in the management of the national park that could reduce the amount of macroplastic pollution.
a. improve city waste disposal
b. recycling programs
c. place litter containers/garbage cans close to camping sites
d. fines for those causing pollution
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Describe how invasive species such as F. silvestris can have a significant impact on native species.
a. cats/invasive species compete with native species for food/habitat/resources
b. invasive species/cats may reduce/endanger native populations
c. invasive species/cats may change the structure/balance of the food web/chain
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Suggest a method to limit the impact of F. silvestris on native species.
a. control population/sterilization «of cats»/culling/hunting
b. keep household cats indoors
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State the role of an indicator species.
a. early warning system
b. provide information on environmental conditions/ecosystem
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Identify possible approaches to maintain the population of P. sandwichensis.
a. ex-situ/zoos/captive breeding
b. control predators
c. in-situ/management of natural reserves/breeding habitats/parks/resources/clean-up pollution
d. education
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Outline three issues arising from the release of pollutants into the environment.
a. reduction in biodiversity
b. biomagnification occurs
c. change in abiotic conditions
eg: loss of soil quality/loss of ozone layer
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Evaluate the impact of the introduction of a namedinvasive alien species into an environment.
Eg gray squirrel
take over the niche of other organisms
e. can reproduce more than native species
f. relationship with predators
g. reduction in the numbers of endemic species / decrease in biodiversity
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Define invasive alien species.
organisms that are introduced (accidentally or deliberately) and negative environmental consequences
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Discuss the global impacts of invasive alien species.
a. inter-specific competition/alien species may out-compete native species
b. lack of predators may allow alien species to thrive / reproduce more rapidly
c. alien species may utilize areas/ resources that native species cannot
d. predation by invasive species can cause loss of biodiversity
e. can lead to species extinction
f. alien species may introduce new diseases
g. global shipping/air travel allows rapid transfer of alien species to new ecosystems
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outline biological control of an invasive alien species.
a. rabbits introduced into Australia
b. controlled by release of myxomavirus / myxomatosis (from South America)
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consequence of marine plastic pollution.
a. organisms may get tangled in plastic debris
b. animals accidentally eat plastic mistaking it for food/feed plastic pieces to offspring
c. (floating) plastic debris can block sunlight preventing photosynthesis
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Explain the consequences of biomagnification.
a. chemicals (non-degradable) accumulate along the food chain becoming more concentrated at each successive trophic level
b. negative effects of organisms high in food chain
c. toxic effects/death/ thin egg shells/other valid example
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Phosphate can be lost from agricultural land in several different ways. State one of these.
run-off/removed by the harvesting of agricultural crops
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Describe how the changes in world rock phosphate production after 1985 may have affected world food supplies.
phosphorus is important as a fertilizer
b. a drop in phosphate could lead to less agricultural output
c. «this could mean» less food available for increasing population
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Distinguish between ex situ and in situconservation of endangered species.
ex situ is in artificial environment, in situ is in natural environment
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Outline how plastic ingestion may lead to biomagnification in these marine species.
a. plastic broken down into microplastics to be able to enter the food chain
b. plastic/microplastics become more concentrated at each trophic level
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Describe the use of indicator species in monitoring environmental change
a. presence/absence indicate environmental conditions
b. changes in the environment affect these species
c. relative numbers of individuals/indicator species can be used to calculate a biotic index
d. changes monitored over time
e. changes can lead to measures to protect the environment
f. e.g. Tubifex for sediment pollution
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Describe one method that could have been used to estimate the population size of a given tree in a forest after fire damage had occurred.
a. transect through a given area
b. trees counted on transect
c. calculation of total population considering area
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Outline how the edge effect can affect diversity in forests.
a. edge effect are the changes in community structures that occur at the boundary of two habitats
b. areas with small habitat fragments exhibit especially pronounced edge effects
c. edge species will always have a habitat
d. if patches of forest are too small the non-edge species cannot find a habitat
e. overall non-edge biodiversity is lower
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Define indicator species.
organism that is present/absent when specific environmental conditions exist
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Discuss two advantages of ex situ conservation measures.
a. raise awareness / gain widespread public/political support for conservation actions
b. education/research opportunities
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State the two components needed to calculate the biodiversity of an area.
a. number of organisms of each species present
b. total number of species
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Explain biogeographic factors that increase the effectiveness of nature reserves.
a. large area can support greater range of habitats / longer food chains / higher population numbers
b. low edge effect with circular reserves
c. intact / unbroken areas represent less disturbance on habitats
d. fragmented areas linked by corridors
e. (proximity of fragmented areas) allows for animal movement / genetic exchange
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Suggest reasons for the differences in predation.
a. the marmots have experience with/recognise predators
b. parents shield them from predators
c. those born in the wild are favoured in natural selection
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Distinguish between ex situ and in situconservation of endangered species.
ex situ is in artificial environment, in situ is in natural environment
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Outline a named example of the captive breeding and reintroduction of an endangered animal species.
eg Giant panda
eg loss of habitat/hunted for fur
eg in zoos/ex situ/in situ/China
eg bred/raised in captivity
eg relative success re: introducing to wild/some reproduction in zoos
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State two bottom-up factors affecting algal blooms.
minerals
phosphorus
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Explain how top-down factors control algal blooms.
a. the herbivores/first consumers regulate algal bloom
b. predators of the herbivores help regulate algal bloom/reduce herbivore abundance
c. overfishing/death of predators/decreased reproduction of predators decreases algal bloom as herbivore population increases
d. habitat degradation can decrease algal bloom
e. pathogens of algae will decrease algal bloom
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Discuss the factors affecting population growth that can result in an exponential growth curve.
a. exponential growth occurs in ideal/unlimited environment
b. population growth determined by natality, mortality, immigration and emigration
c. natality / births / reproduction increases population
d. as long as natality is higher than mortality
e. low mortality leads to exponential growth
f. absence of limiting factors will lead to exponential growth
g. limiting factors could be competition for resources/habitat / presence of predators/diseases
h. higher mortality and/or emigration compared to natality and/or immigration cause population to decrease/rate of growth to slow
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Explain how nutrients can have a positive or negative bottom-up effect on seagrass.
a. the positive bottom up effect is due to availability of nutrients
b. nutrients increase abundance/plant growth rates
c. the negative bottom-up effect as excess of nutrients causes a bloom in algae growth/eutrophication/competition
d. limited nutrients have negative effect on seagrass growth
e. excess algae cause seagrass to die/decompose/replenish nutrients
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Explain how the population of snails in an ecosystem could be estimated by capture-mark-release-recapture, identifying the limitations in the method.
a. snails in the ecosystem are captured and marked
b. they are released back in to the ecosystem and allowed to mix
c. a second sample of snails are captured in the ecosystem and those that are marked are counted
d. sufficient time given between first and second sample to allow for mixing
e. the ratio of the first sample size to those recaptured marked = the ratio of the number in the second sample to the population/formula
f. area of habitat determined
g. assumes sample size is large enough to be significant
h. assumes there is no emigration/immigration/death of snails
i. assumes the marking of the snail does not affect their survival
j. assumes no misidentification of species
k. assumes marked snails do not lose their marks
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Explain the factors that can contribute to the exponential growth phase in a sigmoid population curve.
a. ideal environment/unlimited resources/below carrying capacity
b. little disease/few predators
c. high natality/birth rate AND immigration
d. natality and immigration greater than mortality and emigration
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Outline the effect of carrying capacity on the growth of a population.
a. carrying capacity is maximum population size/number of individuals that environment can support
b. population growth slows/fluctuates as the carrying capacity of environment reached
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Explain the technique used to estimate the population size of a named species of organism that is able to move.
A. Woodlice
b. capture and count a sample of the population
d. apply a mark that will not affect the survival of the animal e.g. non-toxic paint spot
e. release the organism into the environment
f. allow time to become randomly dispersed
g. capture a second sample and count the complete sample
h. count the marked individuals in the second sample
i. define formula to estimate the population size N=(n1×n2)/n3 where n1 = first capture, n2 = second capture, n3 = number marked in second capture
j. only estimates could be obtained
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Discuss how crop plants obtain the phosphorus that they need to grow and whether the supply of phosphorus to crops is sustainable.
Natural cycle
a. plants absorb phosphorus from the soil by the roots
b. soil phosphorus comes from weathered phosphate rocks
c. soil/organic phosphorus also comes from humus/plant/animal residues/guano/microorganisms
d. phosphorus is a limiting macronutrient factor in plant growth
Sustainability
e. natural phosphorus cycle is slow/not sustainable with increased crop production
f. phosphorus is replenished in the soil by use of mineral/organic fertilizers
g. phosphorus/phosphate is mainly mined from phosphate rocks
h. rocks are becoming used up/inaccessible so non-sustainable/non-renewable
i. increased demand for food/meat/dairy/grain increases demand for fertilizers
j. runoff/erosion/leaching of fertilizers decreases potential supply for crops
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Some scientists estimate that available phosphorus reserves in the Earth will be completely depleted within approximately 100 years. Discuss the implications of these estimates.
a. production of fertilizers will decrease/price of fertilizers will rise
b. less food production / increase in cost of foods
c. development of alternative methods of agriculture
d. Phosphate needed by living organisms for nucleic acids/ATP so lack will affect growth negatively
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The percentage of phosphorus in an ecosystem that is recycled per year is in most cases very small, and far smaller than the percentage of nitrogen that is recycled. Suggest reasons for this difference.
a. largest store of phosphorus in ecosystems is in marine sediments and minerals/phosphate rock while nitrogen is in the atmosphere
b. main source of release of phosphorous is by weathering of rocks very slow process/ nitrogen is by bacterial action
c. high concentrations of nitrogen/low concentration of phosphorous compounds in living organism
d. phosphorus is not a very soluble mineral
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Suggest how nitrogen and phosphate cycles can be disrupted by humans or extreme weather events.
a. excess rains/floods/irrigation can wash away nutrients/N/P by leaching;
b. excess rains/floods/irrigation can lead to waterlogged soils;
c. waterlogging leads to denitrification due to anaerobic conditions;
d. nutrients are added to the cycles by application of fertilizer;
e. nutrients are removed by the harvesting of agricultural crops;
Nitrogen:f. lightning increases N in soil;
g. planting legumes increases N in soil;
Phosphate:h. mining of P speeds up the P cycle/depletes P reserves;
i. phosphorus is added to waters in detergents;
j. phosphorus is mined/taken from rocks for making detergents/fertilizers;
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Discuss the causes and consequences of eutrophication.
causes:a. excess nutrients/nitrates/phosphates in an aquatic system
b. natural runoff from soil/erosion/weathering of rocks
c. runoff of fertilizers «from agricultural land/golf courses»
d. partially treated sewage/animal waste discharged into waterways
consequences:
e. algal blooms
f. blocks light for photosynthetic organisms
g. dead organisms sink to bottom of water and decompose
h. decomposers/microorganisms increase BOD/use oxygen
i. oxygen/DO availability for other organisms decreases
j. decrease in biodiversity/disappearance of organisms
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Describe reasons that the availability of phosphates may become limiting to agriculture in the future.
a. phosphate-rich rocks/resource is limited
b. demand exceeds availability of phosphorus
c. cycling of phosphorus is slow
d. as crops are removed, the phosphate levels within the soil is continually depleted
e. there is no biological/industrial way to replenish the mineral fast enough
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Explain how eutrophication can occur from the excessive use of phosphates.
a. phosphates are leached to lakes/rivers
b. induces incremental growth of plants/bloom/algae
c. algae do not let light go through water so less photosynthesis
d. plants/algae die/decay
e. bacterial decomposition consumes the oxygen
f. creating state of hypoxia
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Explain how an ecological community structure could be affected by the removal of a keystone species.
a. keystone species have a main/disproportionate role in the maintenance of the structure of a community
b. not necessarily top predator
c. may impact a top-down/bottom-up control
d. if removed cause increase in populations of secondary consumers and decrease of primary consumers
e. if removed may cause loss of balance in food chain/community
eg: honey bees
eg: pollinate flowers
eg: plant reproduction is reduced
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Explain how human activities could affect the phosphorus cycle.
a. phosphorus in rock (reserves) enters slowly into the biosphere by weathering
b. mining of phosphorus (-bearing) rocks accelerates the natural cycle/faster than natural erosion
c. (mined) phosphorus is made into fertilizers/animal feeds/other products
d. (phosphorous products) transported to agricultural areas (all over the world)
e. with use of fertilizers phosphorus makes its way into the soil
f. run-off/drainage from farms causes phosphorus to move into aquatic ecosystems
g. use of detergents adds phosphorus to water
h. release of sewage adds phosphorus to water
i. excess phosphorus can lead to over growth of algae and plants in water
j. decomposition of dead plant material (by bacteria) use up all the oxygen in the water/increase BOD
k. eutrophication can kill fish and other plants / is negative for ecosystems
l. phosphorus removed (from ecosystem) by the harvesting of agricultural crops
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Commercial fertilizers are often applied to agricultural land. Discuss the use of fertilizers on crops and their effect on other ecosystems.
a. adding fertilizer increases nitrogen/phosphate in soil/nutrient cycles
b. adding fertilizer increases crop yield
c. commercial fertilizers may not stay in ground as long as organic fertilizers/manure
d. commercial fertilizers release compounds more rapidly than organic fertilizers/manure
e. nutrients run off/leached from land into water/groundwater/lakes/streams
f. high concentrations of nitrogen/phosphate in water causes eutrophication
g. high concentrations of nitrogen/phosphate causes algae to multiply rapidly
h. algae die and decomposed by bacteria
i. decomposers require oxygen from water
j. if oxygen levels drop too low fish/aquatic organisms die
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Describe the major characteristics of a eutrophic lake.
a. normally shallow
b. low water visibility
c. high net primary productivity
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What do nitrogen-fixing bacteria do?
Nitrogen-fixing bacteria convert atmospheric nitrogen to ammonia.
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What is the mutualistic relationship between Rhizobium and roots?
Rhizobium associates with roots in a mutualistic relationship.
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What do denitrifying bacteria do in the absence of oxygen?
In the absence of oxygen denitrifying bacteria reduce nitrate in the soil.
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How can phosphorus be added to or removed from the phosphorus cycle?
Phosphorus can be added to the phosphorus cycle by application of fertilizer or removed by the harvesting of agricultural crops.
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How does the rate of turnover in the phosphorus cycle compare to the nitrogen cycle?
The rate of turnover in the phosphorus cycle is much lower than the nitrogen cycle.
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What could become limiting to agriculture in the future?
Availability of phosphate may become limiting to agriculture in the future.
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What is the consequence of leaching mineral nutrients from agricultural land into rivers?
Leaching of mineral nutrients from agricultural land into rivers causes eutrophication and leads to increased biochemical oxygen demand.
