topic C Flashcards
what is the distribution of species affected by?
limiting factors
define limiting factors
the factor that is most scarce in relation to an organism’s needs
Limiting factors can be either
biotic (living) or abiotic (non-living):
- Biotic factors include interactions between organisms – either intraspecific (within species) or interspecific (between species)
- Abiotic factors include environmental conditions – such as light, temperature, salinity, rainfall, wind velocity, soil pH, etc.
describe the law of tolerance
According to the law of tolerance, populations have optimal survival conditions within critical minimal and maximal thresholds
As a population is exposed to the extremes of a particular limiting factor, the rates of survival begin to drop
The distribution of a species in response to a limiting factor can be represented as a bell-shaped curve with 3 distinct regions:
- Optimal zone – Central portion of curve which has conditions that favour maximal reproductive success and survivability
- Zones of stress – Regions flanking the optimal zone, where organisms can survive but with reduced reproductive success
- Zones of intolerance – Outermost regions in which organisms cannot survive (represents extremes of the limiting factor)
draw a normal distribution curve (labelled) for the distribution of a species
what can we use to correlate the distribution of a plant or animal species with an abiotic variable?
- line transects: a tape is laid along the ground between two poles. sampling can be confined to describing all of the organisms that touch the line or distance of samples from the line
- belt transects: where sampling is carried out between two lines separated by a fixed distance
- point transects, used mostly in studies of bird populations: researcher stands at randomly selected points and makes observations within a certain radius
describe the niche concept
each species plays a unique role within a community because of the unique combination of its spatial habitat, how it obtains food, and its interactions with other species
define the competitive exclusion principle
two species cannot survive indefinitely in the same habitat if their niches are identical.
describe what would happen in the case of completely overlapping niches
- the two species cannot coexist in the same habitat
- either one species will lead to the decline and extirpation of the other, or one or both of the competitors will narrow their niches to avoid competition
describe the difference between fundamental and realised niches
the fundamental niche of a species is the potential mode of existence, given the adaptations of the species. it refers to the broadest range of habitats it can occupy and roles it can fulfil. The realised niche is the actual mode of existence, which results from the combination of its adaptations and competition with other species
give 5 types of interspecific interactions
herbivory: primary consumers feeding on producers
predation: a consumer feeding on another consumer
parasitism: when one organism feeds off another but does not normally kill it
mutualism: two species live in a close association where both organisms benefit from the association
commensalism: one organism benefits and the other is neither harmed nor helped.
describe the symbiotic relationship between zooxanthellae (photosynthetic algae) and reef-building coral reef species
- the coral provides the alga with a protected environment and a substrate that can hold it in place for photosynthesis to occur
- the zooxanthellae provide the coral with molecules such as glucose and amino acids
define a keystone species and its effects
a keystone species is one which has a disproportionate effect on the structure of an ecological community
fundamentally supports the whole structure and prevents it from collapsing
give 3 ways keystone species may influence a community
Predators – they can exert pressure on lower trophic levels to prevent them from monopolising certain resources
Mutualism – they can support the life cycle of a variety of species within a community (e.g. pollinators / seed dispersal)
Engineers – they can refashion the environment in a manner that promotes the survival of other species
most species occupy —— trophic levels in —— —— ——-
different; multiple food chains
what does a food web do?
it shows all the possible food chains in a community
from what may we be able to predict the type of stable ecosystem that will energy in an area?
from the climate
describe how temperature may affect the distribution of organisms
- influences rates of cell respiration, photosynthesis, decomposition, transpiration
- impact on productivity
describe how precipitation may affect the distribution of organisms
- influences rates of photosynthesis (the photolysis of water is essential for non-cyclic photophosphorylation) and decomposition
- impacts productivity
what depends on respiration rate?
the percentage of ingested energy converted to biomass
give the equation for net production value
net production= gross production - respiration
define gross production
the total amount of organic matter produced per unit area per unit time by a trophic level in an ecosystem
define net production
the amount of gross production remaining after subtraction of the amount used for respiration by the trophic level.
describe how gross production, total biomass, and total community respiration vary including a graph
Early stages of primary production:
- high availability of sunlight=> high gross production
- little biomass=> low total amount of respiration.
As succession proceeds:
- biomass increases=> increasing respiration
Later:
- all spaces for stems become filled=> gross production declines
- equilibrium reached:
total community production: total community respiration = 1
what is the effect of disturbance to an ecosystem?
it influences the structure and rate of change within ecosystems
define secondary succession
the progression of communities where a pre-existing climax community has been disturbed but the soil is already developed
what is secondary succession initiated by?
by a change in conditions
describe the effects of disturbance on an ecosystem
- close to time of disturbance, rate of system respiration, productivity, and species diversity increase rapidly and there is an accumulation of biomass
- as succession proceeds, the pace of change slows.
describe primary succession
Occurs when communities develop on entirely new land without any established soil (ie at river deltas, glaciers, sand dunes or on exposed rock)
- organisms which first colonise the region are called pioneer species and typically consist of lichen or moss
- as the lichen and moss die, they decompose, which creates the first organic soil capable of sustaining plant growth
- as plant species colonise the area, the litter produced by their growth and their decomposing remains will cause soil depth, mineral content, and water retention to increase
- this will allow for the growth of larger plants, which will reduce erosion through the binding action of their roots
- larger plants will eventually outcompete smaller shade intolerant plants
give 5 examples of aspects of an ecosystem that you could investigate
- species diversity
- nutrient cycling
- water movement
- erosion
- leaf area index
closed system
energy but not matter is exchanged with the surroundings
isolated system
theoretical; exchange neither matter nor energy with their surroundings
open system
exchange matter and energy with their surroundings
define feed conversion ratios
the quantity of dietary input in grams required to produce a certain quantity of body mass in livestock or fish.
give an example of how humans interfere with nutrient cycling
agriculture
- phosphate is mined, converted to fertiliser and used.
- nitrogen is produced from gaseous N2 in the Haber process has increased inputs into the n cycle
- these are added to the soil so that agriculture can occur.
construct and explain a gersmehl diagram for taiga
check
construct and explain a gersmehl diagram for desert
check
construct and explain a gersmehl diagram for tropical rainforest
check
what is a gerhsmehl diagram?
a model of nutrient storage and flow for terrestrial systems
tropical rainforest
- most nutrients stored as biomass; litter is rapidly decomposed and vast roots quickly draw nutrients from soil
- there is a fast rate of transfer between stores; hot and wet weather conditions promote precipitation, runoff, weathering, and leaching
taiga
- most nutrients stored as litter; low temperatures slow decomposition which delays nutrient transfer to soil and biomass
- there is little nutrient gain from precipitation or weathering due to low levels of rainfall (cold temperatures produce snow)
- there is little nutrient loss via leaching (due to low rainfall) but surface runoff may be high at certain times (if the snow melts)
desert
- most nutrients stored in the soil (few plants exist to store nutrients as biomass or produce litter)
- there is little nutrient gain from precipitation and little nutrient loss via runoff due to very low levels of rainfall
- the amount of weathering and leaching is negligible
what is the problem with alien species being introduced?
they can escape into local ecosystems and become invasive.
endemic species
species native to an area
alien species
species that are not native but are introduced by humans
what is an invasive species?
a species that increases in number and spreads rapidly
why are many alien species invasive?
because the normal limiting factors in their original habitat are missing (eg predators, diseases, competitors).
give 2 examples of harmful impacts of alien species
- excessive predation of native species
- interspecific competition due to niche overlap with native species
—– —— and the —— – —— can lead to a reduction in the numbers of endemic species when alien species become invasive
competitive exclusion; absence of predators
define the competitive exclusion principle
two species with overlapping niches cannot continue occupying overlapping niches indefinitely
give 2 possible effects of competition between endemic and alien species
- either or both species may occupy smaller realised niches
- the ability of a new ecosystem to resist an alien species can prevent it from becoming invasive
define bioaccumulation
the build up of toxins in the body of organisms
when is bioaccumulation most likely to happen?
when the toxin is fat-soluble and not easily excreted
define biomagnification
the process by which chemical substances become more concentrated at each trophic level
why does biomagnification happen?
at each stage in a food chain, the predator consumes large quantities of prey during its lifetime and bioaccumulates the toxins that they contain.
——– AND ——- have accumulated in marine environments
microplastic; microplastic debris
describe the causes and effects of plastic accumulation in the ocean
causes:
- direct disposal from ships and platforms
- litter being blown into water systems
effects:
- degradation of the plastic at sea releases persistent organic chemicals that can bioaccumulate/magnify
- plastics absorb other persistent organic chemicals and thus concentrate these toxins
- animals eat/become tangled in plastic
give two examples of when biological control can go wrong
Cane toad
- introduced to Australia to control the cane beetle
- has become a generalist predator and competitor for food resources
- big ecological impact on predator that consume the toad (as it is lethal to consume)
Zebra mussel:
- invasive species of the North American Great Lakes system that is native to the Black/Caspian Sea.
- brought by empty cargo ships
- populations can grow so dense that they block pipes, municipal water systems or interfere with hydroelectric power generation
define biological control
involves using a living organism (or a virus) to control an invasive species
define eradication programmes
involve application of herbicides or selective harvesting of invasive plants, and trapping/culling of invasive animals
describe the uses, benefits and risks of DDT
Insecticide used to control vector diseases and in agriculture.
- DDT pollution is biomagnified up food chains, and leads to birds of prey having thin-shelled eggs and failing to reproduce successfully.
- in humans it can cause reduced fertility, genital birth defects, cancer, damage to developing brains, and its metabolite, DDE can block male hormones
- accumulates in body fat/breast milk and persists in the environment for decades.
It is very good for malaria vector control- when the use of DDT was discontinued for malaria vector control, malaria rates climbed.
Give 2 case studies for plastic pollution
Laysan albatross:
- nests on islands found in the North Pacific gyre, where large amounts of plastic debris is found
- feeds by skimming the ocean surface with their beak, causing them to ingest large quantities of plastic
- adults can regurgitate the plastics they have swallowed, but chicks are unable to – as such it fills up their stomachs
- mortality rate is high
Sea turtles:
- commonly mistake plastic bags for jellyfish
- ingestion of the plastic can be fatal – the plastic can become lodged in the esophagus and cause future feeding problems
- debris can also become wrapped around the turtle, restricting movement and developmental growth
define an indicator species
an organism used to assess a specific environmental condition
why are certain species good indicators?
because they only occur when specific environmental conditions are present
how can we calculate the value of a biotic index?
by using relative numbers/frequencies of indicator species
state the equation for biotic index
check
A high biotic index indicates
the presence of many pollution-sensitive organisms, denoting an unpolluted environment
A low biotic index indicates
a relative abundance of pollution-tolerant organisms, denoting a polluted environment
define in situ conservation
measures involving endangered species remaining in the habitat to which they are adapted
in situ conservation may require
active management of nature reserves or national parks, eg:
- controlled grazing
- removal of shrubs and trees
define ex situ conservation
measures involving removal of organisms from their natural habitat.
state a case study of the captive breeding and reintroduction of an endangered animal species
Peregrine falcon
- became endangered because of the widespread use of DDT
- conservation workers collected eggs from nests and replaced them with porcelain replicas , then incubated them
- this ensured a greater frequency of hatching
state the two components of biodiversity
richness and evenness
define richness
the number of different species present
define evenness
how close in numbers each species is
give the formula for Simpson’s reciprocal index of diversity
check
what does the Simpson’s reciprocal index of diversity do?
it quantifies biodiversity by taking richness and evenness into account
the higher the value of D, the higher the biodiversity.
—— ——- can affect species diversity
biogeographic factors
analyse the impact of island size on diversity
Biodiversity is proportionate to island size
Larger islands:
- support a greater range of habitats (and hence more available niches for species to occupy)
- sustain higher population numbers for each species (increases species evenness)
- greater productivity at each trophic level, leading to longer and more stable food chains
analyse the impact of edge effects on diversity
Edge effects occur at ecotones (where two habitats meet and there is a change near the boundary). More species exist at ecotones as species from different habitats converge leading to increased predation and competition.
However certain species may not be able to thrive under these conditions and instead must occupy more central regions.
These effects depend on the particular abiotic conditions.
what is the use of sampling techniques?
estimating population size- involves determining the population size in a small area and using this to estimate the entire population
describe how the Lincoln index is used
capture-mark-release-recapture used to estimate population size
- capture as many individual as possible in area occupied by animal population using netting, trapping or careful searching
- mark each individual, without making them more visible to predators
- release all the marked individuals and allow them to settle back into their habitats
- recapture as many individuals as possible and count how many are marked and how many unmarked
- calculate estimated population size by using Lincoln index
Lincoln index
n1 x n2
/ n3
n1- no caught and marked initially
n2- no caught on second occasion
n3- no recaptured
draw and describe time-number population curve for fish, and sustainable yield curve as well
page 644
evaluating methods used to estimate the size of commercial stock of marine resources - random sampling
most fish species are highly mobile and unevenly distributed
evaluating methods used to estimate the size of commercial stock of marine resources - capture-mark-release-recapture
useful in lakes and rivers, but the numbers of recaptured fish are usually too small in the open ocean for reliable estimations
evaluating methods used to estimate the size of commercial stock of marine resources - fish can be temporarily stunned then counted with an electric shock
possible in lakes and rivers but not in oceans
evaluating methods used to estimate the size of commercial stock of marine resources - echo sounders
can be used to estimate size of shoals of fish, but many species do not form shoals
evaluating methods used to estimate the size of commercial stock of marine resources - data obtained from fish catches
age structure of landed fish can be used to estimate population size - spawning rates can be deduced, from which estimates of the total c an be made. however, violators of regulations designed to control the age of fish landed do not report what they land
draw and describe a J shaped population growth curve
exponential growth pattern than occurs in an ideal, unlimited environment §
draw and describe an S shaped population growth curve
when a population colonises a new habitat, there will be a low level of environmental resistance initially, causing the population to grow exponentially. as the environment begins to offer resistance, the population reaches a transition point where the growth rate begins to slow until it reaches the carrying capacity
annotate an S curve
- exponential phase- natality exceeds mortality
- transitional phase- mortality rates begin to increase until natality rate approaches mortality rate. This is due to limiting factors
- carrying capacity reached
4 factors that influence population size
- natality
- mortality
- immigration
- emigration
k
the variable that represents the maximum size of a population that an environment can support - carrying capacity
how are booms or busts brought back to normal
higher rates of mortality will return the population to the carrying capacity of the environment or the population may crash well below this
Limiting population factors can exert their influence via either
top down or bottom up control
top down control
Top down factors are pressures applied by a higher trophic level to control the population dynamics of the ecosystem
The top predator either suppresses the abundance of its prey or alters its behaviour to limit its rate of population growth
Top down control results in an oscillating trophic cascade (suppression at one level increases numbers at the next level)
Keystone species commonly exert top down control by preventing lower trophic levels from monopolising essential resources
bottom up control
Bottom up factors are pressures that limit the availability of resources to lower trophic levels (e.g. producers)
A lack of resources at lower trophic levels suppresses the abundance of organisms at higher trophic levels
Population growth will be reduced for all higher levels as the suppression of the ‘bottom’ restricts energy supply to the ‘top’
Human activity can often limit resource availability and hence inadvertantly exert bottom up pressure on an ecosystem
bottom up control using algae
Algal blooms can be reduced by limiting the supply of nutrients such as nitrogen and phosphorus in the water
This may involve reducing the use of fertilisers for agricultural practices to limit the nutrient input from surface runoff
Nutrient reduction can be expensive to implement and difficult to police, as it requires a concerted community effort
Top Down Control using algae
Algal blooms can be reduced by introducing piscivorous (fish-eating) fish into the aquatic ecosystem
The piscivores will feed on zooplanktivores – and by reducing their numbers, will increase the number of zooplankton
Zooplankton (such as Daphnia) feed on algae, and hence will reduce the population of algae via herbivory
Introducing piscivores can have unintended consequences on food webs and should be done with caution
describe the nitrogen cycle
- nitrogen fixation: nitrogen gas (N2) in the atmosphere is converted to ammonia (NH3) in the soil by:
- mutualistic nitrogen-fixing bacteria in root nodules (eg Rhizobium)
- free-living nitrogen-fixing bacteria in the soil (eg Azotobacter)
- non-living processes, (eg lightning and the Haber process) - nitrification of ammonia (NH3) to nitrite (NO2-) by the genus of Nitrosomonas bacteria
- nitrification of nitrites (NO2-) into nitrates (NO3-) by nitrifying bacteria (eg Nitrobacter)
- denitrification of nitrates (NO3-) into nitrogen gas (N2) in the atmosphere (eg by Pseudomonas denitrificans)
OR
- Uptake and assimilation of nitrates (NO3-) by plants, and subsequently animals.
- Ammonification into ammonia (NH3) by decomposers, (mainly bacteria and fungi)
describe the mutualistic relationship between rhizobium and roots
- plant cannot carry out nitrogen fixation by itself but it is vital for the production of amino acids
- plants passes carbohydrates produced during photosynthesis to the bacteria as an energy source
what are chemoautotrophs? give two examples
they derive energy from inorganic compounds
- nitrobacter
- nitrosomonas
when do denitrifying bacteria reduce nitrate in the soil, releasing gaseous nitrogen as a product?
in the absence of oxygen
give 2 impacts of water logging on the nitrogen cycle
- eutrophication, if the excess water flows off the field and enters water courses as a runoff
- loss of bioavailable nitrogen through denitrification by Pseudomonas denitrificans
oxygen is in —– supply in waterlogged soils
short
state an adaptation of plants living in wetlands and explain the need for it
wetlands have permanently waterlogged soils and would therefore have nitrogen-deficient soils
an adaptation of bog plants is to become insectivorous and obtain nitrogen through the extracellular digestion of animals
what is phosphorous required for in living things?
to produce molecules such as ATP, DNA, RNA, maintain skeletons, and form a component of cell membranes
define the rate of turnover
the amount of phosphorous released from one stock to another per unit time
phosphorous has a relatively —— turnover rate in comparison to nitrogen
low
why does phosphorous have a low turnover rate?
it is only slowly released from rocks into soil/ecosystems by weathering and erosion.
how can amount of phosphorous in the phosphorous cycle be changed?
- added by application of fertiliser
- removed by the harvesting of agricultural crops
how is fertiliser made?
by mining of phosphorous and conversion to phosphate-based fertiliser
how will availability of phosphate resources affect agriculture in the future?
the availability of phosphate will limit agriculture; there is a depletion of phosphate resources that can be mined. without fertilisers, famine would result as yields would plummet
describe eutrophication
- rain can result in the leaching of water-soluble nutrients from agricultural land into bodies of water
- the nutrients favour the growth of algae leading to algal bloom, blocking the light to the plants below
- when the algae and plants below them die, it leads to loss of oxygen due to bacterial activity on the dead organic matter (high BOD)
- fish die
healthy lead
deep green and glossy
leaf from plant with nitrogen deficiency
yellows down the mid vein
leaf from plant with phosphorous deficiency
turns red-purple along the leaf margins
leaf from plant with potassium deficiency
firing and yellowing along the leaf margins
assessing the nutrient content of a soil sample
soil quality assessment kit:
- add chemical to sample
- colour is produced that can be compared to the key or quantified in a colorimeter
compare and contrast exchange of energy with nutrient cycling in ecosystems
both
- flow through ecosystems
- both used for metabolism and growth
energy:
- source is the sun
- lost as heat between each trophic level
- is not recycled
nutrients
- source is soil/rocks
- escape food chains as litter/feces
- recycled
causes of eutrophication
- excess nutrients in an aquatic system
- natural runoff from soil/erosion/weathering of rocks
- runoff of fertilisers
- partially treated sewage
explain what information a pyramid of energy provides about an ecological community
shows the amount of energy at each trophic level measured over a given period of time. The units are energy per area per time. The width/size of each bar represents the amount of energy the bottom level represent the producers, and subsequent levels represent consumers. Each level should be roughly one tenth of the size/10 % of the preceding
level as the energy that enters a community is ultimately lost as heat/in
respiration.
explain why viral diseases cannot be treated using antibiotics
- viruses are not living
- viruses lack metabolism
- antibiotics target metabolic pathways
describe the origin of eukaryotic cells according to the endosymbiotic theory
a. mitochondria and chloroplasts are similar to prokaryotes ✔
b. host cell took in another cell by endocytosis/by engulfing in a vesicle ✔ Allow “taking in” in place of “engulfing”
c. but did not digest the cell/kept the ingested cell alive, developing a symbiotic/mutualistic relationship between engulfed and host cell ✔
d. chloroplasts and mitochondria were once independent/free-living organisms ✔
e. DNA loop in chloroplast/mitochondrion
g. double membrane around chloroplast/mitochondrion ✔
h. 70s ribosomes in chloroplast/mitochondrion ✔
outline a reason in which reef building corals are affected by increasing atmospheric carbon dioxide
- corals have exoskeletons made of calcium carbonate
- CaCO3 shells dissolve in acidic conditions
- high co2/acidic conditions reduce availability of CaCO3 for forming shells
explain how aphid stylets can be used to study the movement of solutes in plant tissues
a. aphids tap into phloem with their stylets «to use sap as a food source»
b. plants grown in radioactive CO2/14CO2 incorporate it into carbohydrate
c. phloem contents/sap/fluid flows through the stylet
d. aphid body severed/cut from stylet «after stylet inserted into phloem»
e. analyze «sap/fluid exuded from stylet» for solutes/carbohydrates
OR
radioactive-labelled carbon can be detected «in the phloem sap»
f. stylets at different parts of the plant can show sequence/rate of movement
explain the effects of auxin on plant cells
a. increases cell elongation/growth/enlargement OR has effect on rate of mitosis
b. changes the pattern of gene expression
promotes transcription of some genes
c. changes the pH of the extracellular environment/cell wall and
increases activity of proton pumps
d. breaks cross links/connections between cellulose fibres in cell wall
e. increases cell wall plasticity
f. «varying» auxin concentrations have different effects in different parts of
the plant
explain changes in biomass for the biomass-respiration graph
- initially there is low competition for sunlight/resources
- photosynthesis allows accumulation of biomass
- biomass rises as larger plants replace smaller plants
- in later stages biomass increase limited due to competition for resources
- biomass stabilizes as climax community reached
explain why biomass continues to increase after the respiration levels plateau
a. development of mature trees requires xylem/wood
b. xylem/wood contributes to biomass but not respiration
c. photosynthesis/production greater than respiration
d. photosynthesis/production continues to accumulate biomass
OR
accumulated biomass remains/increases
what do ocean currents do to plastic debris
they concentrate them
outline the requirements for sustainability within a sealed mesocosm
- photosynthetic organisms/autotrophs/plants as producers;
- light (as energy source) for photosynthesis;
- nutrient/water recycling (by saprotrophs);
- decomposers/saprotrophs to breakdown (toxic) wastes;
outline primary succession
colonization of areas that were barren/not previously inhabited/not occupied by organisms;
outline processes that must occur over time to produce deeper soil
- weathering of rock accumulates matter (allowing pioneer species to grow);
- death/decomposition of organisms increase organic matter/detritus/litter;
- increased soil allows larger/more plants to grow / roots preventing erosion;
- as more plants are decomposed, soil depth/amount of soil available increases;
explain how levels of PCBs increase so greatly over trophic levels
- as producers/algae take in nutrients, they also collect/absorb PCBs;
- consumers can take in PCBs directly from the water;
- PCBs are not digested/metabolized;
- PCBs build up in cells/tissues / bioaccumulate;
- PCBs pass on to higher level consumers or
organisms in the higher trophic levels accumulate more; - At each trophic level there is biomagnification;
explain how biogeographic factors affect the richness and evenness of biodiversity
- biogeographic features are combinations of species, habitats and physical features
- richness is the number of different species present (in an area)
- evenness refers to relative abundance of the different species (in an area)
- large nature reserves/large islands have greater biodiversity
- large areas have more species/populations/habitats/richness
- connected areas/nature reserves have more diversity than isolated ones/corridors between areas increases biodiversity
- the greater the surface:perimeter ratio, the greater the biodiversity
- edges are transition areas
- circular shape has more biodiversity than rectangular shape;
- biodiversity measured by Simpson’s / diversity index;
Suggest changes in the management of a national park that could reduce the amount
of macroplastic pollution.
- recycling programs
- place litter containers/garbage cans close to camping sites
- fines for those causing pollution or pass littering laws
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.
- random sampling using quadrats
- trees counted in quadrant
- population calculated using area
when are edge effects especially pronounced?
in areas with small habitat fragments
Explain how top-down factors control algal blooms.
- herbivores regulate algal bloom
- predators of the herbivores helps regulate algal bloom
- overfishing/death of predators decreases algal bloom as herbivore population increases
- pathogens of algae will decrease algal bloom
- habitat degredation can decrease algal bloom
Discuss how crop plants obtain the phosphorus that they need to grow
- plants absorb phosphorous from the soil by the roots
- soil phosphorous comes from weathered phosphate rocks and from plant/animal residues
- phosphorous is necessary for ATP and DNA synthesis
Discuss whether the supply of phosphorous of crops is sustainable
- natural phosphorous cycle is slow and not sustainable with increased crop production
- phosphorous is replenished by use of mineral fertilisers
- phosphorous is mined from rocks
- rocks are being used up and non-renewable
- increased demand for food increases demand for fertilisers
Predict the possible effect of global warming on the nutrient fl ow in a taiga ecosystem.
- increased biomass
- increased uptake of nutrients from soil
- increased decomposition of litter
- increased nutrient composition of soil
- ## increased weathering of rocks
Determine whether islands are open or closed ecosystems.
closed because islands do not exchanged matter/nutrients with surroundings
Discuss two advantages of ex situ conservation measures.
- the protection of endangered species by breeding them in captivity
- education/research opportunities
- raise awareness or gain support for conservation actions
Some scientists estimate that available phosphorus reserves in the Earth will be
completely depleted within approximately 100 years. Discuss the implications of these
estimates.
- production of fertilisers will decrease so their price will rise
- increase costs of foods
- development of alternative measures of agriculture
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.
- largest store of phosphorous is in marine sediments and minerals, whilst nitrogen is in the atmosphere
- main source of release of phosphorous is by weathering of rocks, which is a slow process, whilst nitrogen is by bacterial action
- high concentrations of nitrogen vs low concentrations of phosphorous in living organisms
- phosphorous is not a very soluble mineral
Discuss the factors affecting population growth that can result in an exponential
growth curve.
- exponential growth occurs in an ideal, unlimited environment
- population growth is determined by natality, mortality, immigration, and emigration
- natality increases population as long as it is higher than mortality
- low mortality leads to exponential growth
- absence of limiting factors will lead to exponential growth (eg competition for resources)
- draw a sigmoid curve and label it with exponential growth
Compare and contrast food chains and food webs.
- both represent transfer of food/energy in an ecosystem
- in both, organisms are arranged by trophic levels/feeding positions
- one species could occupy different trophic levels in a food web but not a food chain
Define invasive alien species.
organisms that are introduced and have negative environmental consequences
Using one example, outline biological control of an invasive alien species.
- rabbits introduced into Australia
- controlled by release of myxoma virus from South America
Explain biogeographic factors that increase the effectiveness of nature reserves.
- large area can support greater range of habitats
- reduced edge effect minimises competition
- unbroken/intact areas represent less disturbance on habitats
Outline how reserve size and shape can impact edge effects.
- small reserve has greater edge relative to area, increasing edge effect
- changing shape can change the perimeter for a given area and change the edge effect
identify the assumptions made in capture-mark-release-recapture
- assumes sample size is large enough to be significant
- assumes there is no emigration/immigration/death of snails
- assumes the marking of the snails doesn’t affect their survival
- assumes no misidentification of species
- assumes marked snails do not lose their marks
Natural forests in the area around Mangalore contain hardwood trees such as
teak, Tectona grandis, which are deciduous, shedding their leaves once a year.
Suggest, with a reason, when this might happen.
dry season/Jan/Feb
drop leaves to prevent water loss/transpiration since no rainfall for months
Describe how ingested plastics can cause problems to marine birds.
- fill up the stomachs of birds so they feel full and then starve to death
- block the passage of food, causing starvation
how nitrogen and phosphorous cycles are disrupted by extreme weather events
- excess rain/floods washes away nutrients by leaching and can lead to waterlogged soils
- waterlogged soils lead to denitrification due to anaerobic conditions
- lightning increases N in soil
