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how can phosphate be lost from agricultural land?

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1

how can phosphate be lost from agricultural land?

  • leaching

  • run off

  • removed by harvesting of agricultural crops

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2

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

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3

gersmehl diagram

models nutrient stores and flow in an ecosystem

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4

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

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5

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)

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6

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 doesnā€™t affect their survival

  • assumes there is no misidentification of species

  • assumes marked species do not lose their markings

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7

invasive species

overlap with native speciesā€™ niches

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8

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

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9

exponential growth phase

  • ideal environment/unlimited resources/below carrying capacity

  • little disease/few predators

  • high natality rate and immigration, greater than mortality and emigration

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10

carrying capacity

  • maximum population size that an environment can support

  • population growth fluctuates as the carrying capacity is reached

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11

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

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12

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

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13

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

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14

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

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15

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