how can phosphate be lost from agricultural land?
leaching
run off
removed by harvesting of agricultural crops
effects of changes in world rock phosphate production.
phosphorus is important as a fertilizer
a drop in phosphate could lead to less agricultural output
less food available for increasing population
gersmehl diagram
models nutrient stores and flow in an ecosystem
competitive exclusion
two species that occupy a similar niche in the same location cannot coexist
one of the two competitors will always have an advantage over the other
leads to extinction/displacement/evolution of the second competitor
the niche of one or both competitors becomes narrower
keystone species
they have a disproportionate effect on the biological community (removal of one, leads to more the one below, leading to a reduction of the one below the second)
capture-mark-release
a species is captured and marked
release back into the ecosystem and allowed to mix
a second sample is captured
sufficient time given between the first and second capture to let them mix
area of habitat determined
assumes there is no emigration/immigration/death of snails
assumes the marking of the snails doesnāt affect their survival
assumes there is no misidentification of species
assumes marked species do not lose their markings
invasive species
overlap with native speciesā niches
indicator species
need particular environmental conditions
change in population over time shows effect of environmental conditions
used to calculate biotic index
high index number (10) indicates totally unpolluted
exponential growth phase
ideal environment/unlimited resources/below carrying capacity
little disease/few predators
high natality rate and immigration, greater than mortality and emigration
carrying capacity
maximum population size that an environment can support
population growth fluctuates as the carrying capacity is reached
example of captive breeding
Giant panda
endangered due to loss of habitat/hunting for fur
bred in zoos/ex situ/China
programme was carried out by breading/raising in captivity
relative success re-introducing to the wild
use of fertilisers on crops and their effect on other ecosystems
adding fertiliser increases nitrogen/ phosphate in soil
adding fertiliser increases crop yield
commercial fertilisers may release compounds more rapidly but not stay in the soil for as long as organic fertilisers
nutrients run off into water
high concentrations of nitrogen/phosphate causes eutrophication and algae to multiply rapidly
algae die and are decomposed by bacteria
bacteria require oxygen from water (high BOD)
if oxygen levels drop too low, aquatic organisms die
evaluate the methods used to estimate populations of marine organisms
sampling does not count every organism so it may not be a true estimate
highly mobile marine organisms are unevenly distributed so difficult to estimate
quadrants used to calculate stationary organisms
useful on rocky shores, beaches
capture-mark-release for mobile organisms in restricted environments
fish maybe estimated this way
echolocation to estimate fish populations
echolocation cannot distinguish between species
discuss how crop plants obtain the phosphorus that they need to grow and whether the supply of phosphorus to crops is sustainable
plants absorb phosphorus from the soil by the roots
soil phosphorus comes from weathered rocks
phosphorus is a limiting factor in plant growth
phosphorus cycle is too slow
it is replenished by fertilisers
mined from rocks
rocks are non-sustainable
increased demand for food increases demand for fertilisers
runoff of fertilisers decreases potential supply for crops