classnotes20 - Biomes: Before discussing communities, we...

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Biomes: Before discussing communities, we want to spend a little time describing the different kinds of habitats that can be found on our planet. - As mentioned on the first day of class in 103, all life on the planet can be considered to be in the “biosphere”. - Your text is not terribly generous here - it starts with the Himalayas on one end and oceanic trenches on the other. - Life (bacteria, pollen, spores, etc.) extends much higher up in the atmosphere than the Himalayas - While oceanic trenches are about as deep as things go, bacteria have also been found in rocks several miles under the surface! But it's kind of hard to talk about the “biosphere” and get a good picture of life. Let's go down a level to what are called biomes. - These are large areas with similar environments. They don't have to be in the same area. - Some biomes are a bit arbitrary, and most certainly don't have hard boundaries, but they do give us a way to talk about different environments. - In the water, biomes are defined by such things as temperature, salinity and depth. - On land, it's mostly rainfall and temperature (though other things such as amount of sunlight and wind can be important). Aquatic biomes: An obvious division is fresh vs. salt water. Fresh water environments vary quite a bit: streams, rivers, lakes, ponds, swamps, deltas, estuaries are all a bit different (deltas and estuaries can be saline). In salt water, light levels are also very important [Fig. 34.6A, p. 688] - Starting with intertidal zones, oceans can get to 10,000 m deep. Light levels continue to drop until they become non-existent around 1,000 m
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classnotes20 - Biomes: Before discussing communities, we...

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