אקולוגיה של אקוסיסטמות

1. אקולוגיה שלאקוסיסטמות אקוסיסטמההיא חברה של אורגניזמים יחד עם מכלול יחסי הגומלין בינם לבין עצמם ובינם לבין סביבתםהאביוטית אקוסיסטמההיא יחידה בסיסית באקולוגיה

2. Biogeochemical Cycles A biogeochemical cycle is the cyclic movement of a substance (for example, water, carbon, nitrogen, or phosphate) through the biotic (living) and abiotic (non-living) environments. Biogeochemical cycles are a key component of ecosystems ecology.

3. The Carbon Cycle Understanding of the carbon cycle is critical for global climate change, yet it remains incomplete.

4. The Nitrogen Cycle Note the key role of mutualism between nitrogen-fixing bacteria and their plant hosts. Not shown is the huge contribution of anthropogenic (man-made) ammonia and nitrates.

5. Humans Play a Major Role in the Nitrogen Cycle Aerial fertilization (with nitrogen) of sugar beets.

6. Excessive Amounts of Nitrogen Fertilizer Harm Ecosystems A seasonal “dead zone” where virtually all marine life is killed stretches off the Mississippi Delta. Why? About 1.5 million metric tons of nitrogen from fertilizer runoff promotes algal and bacterial blooms that deplete oxygen from the water.

7. The Water Cycle Only about 40% of precipitation on land comes from water evaporated over oceans; roughly 60% comes from transpiration of water through plants.

8. The Percentage of Available Global Freshwater is Very Small

9. Freshwater Is a Precious and Often Scarce Resource

10. We’re in the Driver’s Seat - Human Activities Dominate Many Biogeochemical Cycles

11. How is Energy Moved and Utilized in Ecosystems? Trophic levels are the “steps” in a food chain moving from producers to different levels of consumers. The efficiency of energy transfer between different levels puts a limit on the number of trophic levels.

12. A Food Web Describes the Way Energy is Transferred Within an Ecosystem