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L01 Ecosystems-what are they


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L01 Ecosystems-what are they

  1. 1. Ecosystems – what are they ? (Refer to Essentials of Ecology, G. Tyler Miller)
  2. 2. Ecosystems <ul><li>Levels of organization </li></ul><ul><li>Individual/Organism </li></ul><ul><li>Population </li></ul><ul><li>Community </li></ul><ul><li>Ecosystem </li></ul><ul><li>Biosphere </li></ul><ul><li>an Ecosystem consists of all of the organisms living in a community (or communities) together with the abiotic factors with which they interact </li></ul>
  3. 3. Rocky Shore community – an example <ul><li>the mix of barnacles, algal mats, herbivorous snails on rocks etc. </li></ul><ul><li>the physical environment (dessication, temp, wave action) leads to a vertical zonation pattern </li></ul><ul><li>predation and competition influence distribution eg. snails grazing algal spores, predatory snails eating herbivores </li></ul><ul><li>disturbance opens spaces, allows establishment of new species </li></ul><ul><li>different communities result in different locations </li></ul>Rocky Shore community
  4. 4. <ul><li>Structure of a community is usually the result of many interactions </li></ul><ul><li>results from: </li></ul><ul><ul><li>many competitive interactions </li></ul></ul><ul><ul><li>complex mutualisms </li></ul></ul><ul><ul><li>predators increasing and decreasing </li></ul></ul><ul><ul><li>variety of disturbances through time </li></ul></ul><ul><ul><li>environmental fluctuations and more! </li></ul></ul>
  5. 5. Biomes – ecosystems & communities on a global scale ( Miller Ch 4 Fig 4.8) <ul><li>vegetation structure in different parts of the world is similar in similar environments - even though species are different </li></ul><ul><li>biomes are communities with similar structure </li></ul>Biosphere (ecosphere) - the biosphere (i.e. all ecosystems on earth) is an additional level of organization
  6. 6. <ul><li>Existence of life depends upon </li></ul><ul><ul><li>an energy source (the sun) </li></ul></ul><ul><ul><li>oxygen, carbon, nitrogen and other elements, all of which are part of worldwide geological and chemical cycles </li></ul></ul><ul><li>All ecosystems on Earth are linked via global biogeochemical cycles. </li></ul><ul><li>an ecosystem is all of the organisms living in a community (or communities) together with their abiotic factors </li></ul>
  7. 7. Ecosystem function through <ul><li> Energy flow </li></ul><ul><li> Cycling of materials </li></ul><ul><li>A systems approach attempts to understand </li></ul><ul><ul><li>the way energy is passed through the system </li></ul></ul><ul><ul><li>how nutrients are cycled </li></ul></ul><ul><li>Individual organisms or species can be considered in terms of the function they perform </li></ul>
  8. 8. What does biodiversity actually do ? biological diversity allows the different ecosystem functions to be carried out the primary ecosystem functions are to <ul><ul><li>Capture </li></ul></ul><ul><ul><li>Store </li></ul></ul><ul><ul><li>Transfer </li></ul></ul><ul><ul><li>Energy </li></ul></ul><ul><ul><li>Carbon dioxide </li></ul></ul><ul><ul><li>Nutrients </li></ul></ul><ul><ul><li>Water </li></ul></ul>
  9. 10. Miller Ch 4 Fig 4.6 Flow of energy and materials through an ecosystem Systems approach to ecosystem function
  10. 11. Essential characteristics of ecosystems 1. Energy flow <ul><li>Energy flows in a unidirectional way (it does not cycle!) fig 4.13 Miller Ch 4 </li></ul><ul><li>This requires a continuous input of energy into an ecosystem </li></ul><ul><li>Energy source autotrophs heterotrophs </li></ul>
  11. 12. Essential characteristics of ecosystems 1. Energy flow <ul><li>Autotrophs </li></ul><ul><li>(e.g. plants, algae) organisms capable of synthesizing all their required organic molecules from simple organic substances and an energy source </li></ul>
  12. 13. Essential characteristics of ecosystems 1. Energy flow <ul><li>Heterotrophs </li></ul><ul><li>(e.g. animals) </li></ul><ul><li>organisms that cannot synthesize complex organic compounds and must feed on organic material formed by other organisms to obtain energy and necessary molecular building blocks for metabolism and growth </li></ul>
  13. 14. Essential characteristics of ecosystems 2. Cycling of materials <ul><li>Materials (e.g. carbon, nitrogen, phosphorus) are cycled from the abiotic environment, through living organisms, and back to the abiotic environment </li></ul><ul><li>This results from metabolic activities of plants and animals, and organisms such as bacteria and fungi that break down organic matter </li></ul>
  14. 15. Energy in ecosystems <ul><li>All organisms require energy </li></ul><ul><ul><li>maintenance, growth, reproduction, (and movement) </li></ul></ul><ul><li>The energy driving the biosphere (and all ecosystems) is solar radiation, captured via photosynthesis by autotrophs </li></ul><ul><li>about 1% of visible light converted to chemical energy </li></ul><ul><li>about 120 billion tonnes of new organic material produced each year </li></ul><ul><li>about 99% of all organic matter in the biosphere is autotrophs (i.e. mostly plants) </li></ul>
  15. 16. Sunlight - the source of energy for the biosphere Miller Ch 4 Fig 4.14
  16. 17. Photosynthesis <ul><li>Photosynthesis </li></ul><ul><li>6 CO 2 + 12 H 2 O C 6 H 12 O 6 + 6 O 2 + 6H 2 O </li></ul><ul><li>Respiration </li></ul><ul><li>Energy (from photosynthesis) is released and used by the organism when the complex molecules are subsequently broken down during metabolism </li></ul>(+ solar energy)
  17. 18. Productivity in ecosystems ( Refer to David T. Krohne ;Pg 358-366) <ul><li>Primary productivity - the rate at which solar radiation is converted into chemical energy by autotrophs (plants) (amount of material or energy per unit time, e.g. g/m 2 /yr) </li></ul><ul><li>Secondary productivity - the rate at which heterotrophs (animals) convert the chemical energy of their food into new tissue </li></ul>
  18. 19. Productivity in ecosystems <ul><li>However, not all of the energy is converted into new living tissues </li></ul><ul><ul><li>respiration (metabolism) accounts for a large part </li></ul></ul><ul><li>Gross primary productivity - energy fixed in photosynthesis per unit time </li></ul><ul><li>Nett primary productivity - energy fixed in photosynthesis minus energy used in respiration (that is, it is the amount available for harvest at next level) </li></ul>
  19. 20. Productivity in ecosystems <ul><li>A measure of nett primary productivity is the change in biomass per unit time (but be aware of what may have been lost) </li></ul><ul><li>Biomass - the weight of living tissue per unit area (e.g. kg/ha) </li></ul>
  20. 21. What limits primary productivity? <ul><li>(The factors that limit rate of photosynthesis limit production) </li></ul><ul><li>light </li></ul><ul><li>water </li></ul><ul><li>temperature </li></ul><ul><li>nutrients (N, P, trace elements) </li></ul><ul><li>all are essential - the resource in shortest supply will be the one limiting biomass production </li></ul>
  21. 22. Which are the most productive ecosystems on Earth?
  22. 23. Which are the most productive ecosystems? <ul><li>Ecosystem Nett primary World primary </li></ul><ul><li>production production </li></ul><ul><li>(g/m 2 /yr) (billion t/yr) </li></ul><ul><li>Tropical rain forest 2200 37.4 </li></ul><ul><li>Woodland/shrubland 700 6.0 </li></ul><ul><li>Temperate grassland 600 5.4 </li></ul><ul><li>Desert and scrub 90 1.6 </li></ul><ul><li>Swamp and marsh 2000 4.0 </li></ul><ul><li>Open ocean 125 41.5 </li></ul><ul><li>Upwelling ocean zones 500 0.2 </li></ul><ul><li>Algal beds and reefs 2500 1.6 </li></ul>
  23. 24. Productivity through time <ul><li>Primary productivity will vary seasonally depending on environmental conditions </li></ul><ul><li>- ‘growing season’ in agriculture - tropical vs temperate forests </li></ul><ul><li>Productivity may change with the age of an ecosystem (regenerating vs older) Young ecosystems - often a greater proportion of young actively growing tissue </li></ul>