1. 1 Dynamics of Ecosystems Chapter 54-55 Biology Raven and Johnson 7 th Ed

2. 2 Mimicry Batesian mimicry – Palatable insects resemble brightly colored, distasteful species. Mullerian mimicry – Unrelated protected species resemble one another.  predators learn more quickly

3. 3 Mimicry Batesian mimicry – Palatable insects resemble brightly colored, distasteful species. Mullerian mimicry – Unrelated protected species resemble one another.  predators learn more quickly

4. 4 Coevolution and Symbiosis Coevolution involves long-term mutual evolutionary character adjustments of two or more species. – predator-prey interactions – symbiotic relationships  two or more kinds of organisms live together in permanent relationships  commensalism, mutualism, and parasitism

5. 5 Interactions Among Ecological Processes Keystone species – Species that have a particularly strong effect on community composition.  top predators

6. 6 Succession Succession is the process of ecosystems changing from a simple to a more complex structure. – primary succession - occurs in bare or open areas  eutrophication of oligotrophic lakes  Lichens first, then mosses, then larger plants. – secondary succession - occurs following only when soil is already present

7. 7 Carbon Cycle CO2 is formed in many ways, but only photosynthesis can break it down.

8. 8 The Nitrogen Cycle Relatively few types of organisms can fix nitrogen into forms that can be used for biological processes. Nitrogen fixation: N 2 + 3H 2  2NH 3 – Only symbiotic bacteria fix enough nitrogen to be of major significance in nitrogen production. – ammonification – denitrification

9. 9 Nitrogen Cycle

10. 10 The Phosphorus Cycle Phosphates weather from soils into water, enter plants and animals, and are re- deposited in the soil when plants and animals decompose. – Millions of tons are added to agricultural land annually to increase crop production.  Superphosphate- can cause oligotrophication of water sources by “choking”.

11. 11 Phosphorus Cycle

12. 12 Trophic Levels Autotrophs - capture light energy and manufacture own chemical energy – primary producers Heterotrophs - must obtain organic molecules that have been synthesized by autotrophs – consumers

13. 13 Trophic Levels – Primary consumers - herbivores – Secondary consumers - organisms that feed on herbivores – Decomposers - break down complex organic material into simpler compounds – Detritivores - live on refuse of an ecosystem

14. 14 Trophic Levels

15. 15 Trophic Levels Trophic level refers to the feeding level of an organism. – Organisms from each trophic level constitute a food chain.  Interconnected food chains constitute a food web. On average, 10% of the organic matter (energy) transfers from one trophic level to the next.

16. 16 Primary Productivity Primary productivity refers to the amount of organic matter produced from solar energy in a given area during a given period of time. – Gross primary productivity is the total organic matter produced. – Net primary productivity is the amount of organic matter produced that is available to heterotrophs. Secondary productivity - rate of production by heterotrophs

17. 17 The Energy in Food Chains Due to the Second Law of Thermodynamics, food chains are generally limited to three or four steps (trophic levels). – A community’s productivity is ultimately determined by the amount of sunlight it receives. – In northern climates, net primary productivity often increases as the growing season lengthens.

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