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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

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Tolerance limits Figure 3.2

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Figure 50.3 A climograph for some major kinds of ecosystems (biomes) in North America

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World biome map Figure 5.3

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Figure 50.9 The distribution of major aquatic biomes

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Figure 50.13 Zonation in the marine environment Figure 50.8 Lake stratification and seasonal turnover

Figure 50.10 Zonation in a lake Currents

Aquatic Biomes •  Temperature •  Currents •  Nutrients •  Salinity •  Oxygen •  Depth •  Sunlight

•  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.

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Biodiversity “hot spots” Figure 5.20

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Natural medicinal products

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Biodiversity

•  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??

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Human disturbance

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Extinction

Natural extinction •  Extinction is a natural process. As

earth changes, so does it’s flora and fauna.

•  Periods of mass extinctions and radiations (diversity)

•  Extinction has to keep up w/ speciation. (~1 per 1000 yrs.)

Extinction

Human accelerated extinction •  Most major mass extinction in the last 65 mill yrs

is now (cretaceous), by us. •  40-100 sp. going extinct every day: unparalleled •  1000-10000 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

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Extinction 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

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Mass extinctions

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Extinction

What makes a species extinction prone?

•  Critical population size •  Specialists vrs. Generalists •  Animal size (large) •  Range (small) •  Trophic position (high) •  Tolerance to humans •  Behavioral patterns

Passenger pigeon-now extinct

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Reproductive strategies

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Carbon dioxide Temperature

Sea level Arctic ice

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320 ppm: occasional bleaching 320 ppm: occasional bleaching

CO2 in summary

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 Extinction

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U.S. wetland acreage Figure 5.24

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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.

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Endangered species

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Protected lands Figure 5.33

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