Biomes. Biomes 12/1/10. Animals and plants have narrow ranges of tolerance to abiotic factors

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1 Biomes What defines a biome? Where are the lines drawn? What are the major controlling factors? What about aquatic biomes Biomes Animals and plants have narrow ranges of tolerance to abiotic factors This in part determines the biotic components of biomes. These are broad geographic regions determined by temperature and rainfall, and described by their plant communities Tolerance limits Figure 3.2 Figure 50.3 A climograph for some major kinds of ecosystems (biomes) in North America 3-1 World biome map Figure 5.3 Figure 50.9 The distribution of major aquatic biomes 5-1 1

2 Figure Zonation in the marine environment Figure 50.8 Lake stratification and seasonal turnover Figure Zonation in a lake Currents Temperature Currents Nutrients Salinity Oxygen Depth Sunlight Aquatic Biomes Physical as well as chemical boundaries Some Key Points Animals interact with biotic and abiotic factors in ways which shape their survival and distributions Biomes are delineated by abiotic factors, but biotic factors play a role too. Biomes are described by plant communities which are controlled by temperature and precipitation Oceans are different: currents and salinity/oxygen distribution have a major impact - productivity Organisms have tolerance ranges to abiotic factors - both long term and short term effects. 2

3 Biodiversity hot spots Figure 5.20 Natural medicinal products Biodiversity Human disturbance Species diversity: number of different species Genetic diversity: ensuring a healthy gene pool-problems with bottlenecks Ecological diversity: numbers of habitat types - relates directly with species diversity But WHY is it important?? 5-9 Natural extinction is a natural process. As earth changes, so does it s flora and fauna. Periods of mass extinctions and radiations (diversity) has to keep up w/ speciation. (~1 per 1000 yrs.) Human accelerated extinction Most major mass extinction in the last 65 mill yrs is now (cretaceous), by us sp. going extinct every day: unparalleled times natural background rate - what s cause? possibly 20% of current species extinct in next 30 yrs - more than have been named yet! Fastest moving aspect of global change Irreversible 3

4 What causes extinctions? Natural events - climate change, etc. Habitat loss and disturbance Commercial hunting and poaching Predator and pest control Pets/decorative plants Introduction of non-natives Population growth, affluence and poverty Mass extinctions 5-8 Reproductive strategies What makes a species extinction prone? Critical population size Passenger pigeon-now extinct Specialists vrs. Generalists Animal size (large) Range (small) Trophic position (high) Tolerance to humans Behavioral patterns 3-10 Carbon dioxide Temperature Sea level Arctic ice 4

5 CO 2 in summary U.S. wetland acreage Figure ppm: occasional bleaching 345 ppm: sporadic mass bleaching 387 ppm: inevitable long-term decline 450 ppm: rapid decline, reefs cease to be biodiverse 600 ppm: acidification affecting all biota 800 ppm: mid Eocene extinction conditions 1000 ppm: reefs only geological structures. Sixth Mass 5-10 Refugia and habitat fragmentation Some organisms CAN survive in these refugia, but may never get out, or may emerge quite changed Life on Earth Living things cause change Living things respond to change Living things change their environments Living and non-living components of our Earth interact Processes like global warming/climate change follow large-scale patterns, but it is the composition of life on earth that can affect those patterns Ecological systems exist in balance - that balance can be disturbed, and its evolution from there can be difficult to predict. Endangered species Protected lands Figure