Dynamics of Ecosystems

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

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

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

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

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

8. The Nitrogen Cycle • Relatively few types of organisms can fix nitrogen into forms that can be used for biological processes. • Nitrogen fixation: N2+ 3H2 2NH3 • Only symbiotic bacteria fix enough nitrogen to be of major significance in nitrogen production. • ammonification • denitrification

9. Nitrogen Cycle

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. Phosphorus Cycle

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. 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. Trophic Levels

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. 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. 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.