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Chapter 50

Study Notes for all of Ecology (Chapter 50s and 22)

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Biological Sciences
Mary Olaveson

Chapter 52: Ecology and the Distribution of Life 52.1 What is Ecology? N Ecology is the scientific study of the rich and varied interactions between organisms and their environment N Communities are systems embracing all the organisms living together in the same area N Ecosystems are systems embracing all the organisms living together and the physical environment they live in N Biosphere - system that embraces all regions of the planet where organisms live N Environment - encompasses all biotic and abiotic factors N Organisms are both influenced and influence the environment 52.2 How are Climates Distributed on Earth? N Climate - average of the atmospheric conditions found in a region over the long term N Climate is what you expect, weather is what you get N Factors that most strongly affect climates: atmospheric and oceanic circulation patterns N Due to the angle of solar energy arriving at a location, it can cause seasonal variations in temperature, and circulation patterns. (Roughly 0.4 degrees decrease per 110 km away from equator at sea level) N Air temperature also decreases with elevation (rise = expansion = losing moisture) N Global air circulation patterns result from the global variation in solar energy input and the spin of the Earth o N At equator (Tropics), warm air rises, replaced by cool air from 30 North and South. N The coming together of these air masses produces the intertropical convergence zone - where the rising air cools and releases its moisture N The air that moved into the ICZ, is in turn replaced by the air that has risen and cooled N This air warms and heats up and picks up moisture (results in deserts) N At 60 N and S, air rises again and descends at the poles o Rotational speed of Earth at the equator is quite high - air speeds are relatively slower o Rotational speed of Earth at pole is non-existent, air speeds are quite high o Therefore, in the Northern Hemisphere, latitudally moving air masses are deflected to the right; and those in the Southern are deflected left o Air masses moving toward the equator become trade winds (veer to become northeast (coming from north) and south east (coming from south)) o Air masses moving away become Westerly winds N As air masses pass over a mountain, the windward side gets precipitation; the leeward side gets a rain shadow N The air pattern circulation also drives ocean currents N The tradewinds cause a westerly current until a continent is reached (Transfer of heat to high latitudes) www.notesolution.com N The deflection at the continent causes the water to go N or S, where it veers right/left, until another continent is reached - causing a cycle. N Dispersal - movement of an individual to seek new places when local conditions seem unfavourable N Migration - one response to cyclical environmental changes 52.3 What is a Biome? N A biome is a terrestrial environment defined by the growth forms of its plants N The distributions of plants are strongly influcned by annual patterns of termpature and rainfall N Species richness - the number of species present in its communities 1. Tundra N Found in arctic and at high elevations in mountains N Dominated by low-growing perennial plants N Permafrost - soil with water permanently frozen 2. Boreal forest N Found toward equator from Arctic tundra, and at lower elevations in mountains N Long winters, short warm summers N Evergreen trees dominate N Temperate Evergreen forests grow along the western coasts of continents at middle to high latitudes in both hemispheres - winters are verywet and summers are cool and dry 3. Temperate Deciduous Forest N Temperatures fluctuate dramatically though precipitation is relatively evenly distributed N Species rich - insects and amphibians 4. Temperate Grasslands N Dry for much of the year N Precipitation is variant; most plant life converted to agriculture N Mammal rich; plants are adapted to grazing and fire 5. Cold Desert N Found in interiors of large continents in the rain shadows of mountain ranges N Temperature variance is great N Dominated by few shrubs and seed eating animals 6. Hot Desert N More diverse vegetation than cold deserts (Succulent plants) N Rich fauna of rodents, insects, lizards, and snakes 7. Chaparral N Form where cool ocean currents flow offshore N Winters are cool and wet; summers opposite N Lots of rodents supported by abundant annuals 8. Thorn Forest and Tropical Savanna www.notesolution.com N Share same climate N Thorn forests are found on the equatorial sides of hot deserts o Small shrubs and trees that drop their leaves during long, dry winters (Acacia) N Tropical savanna have expanses of grasses and grasslike plants with scattered trees o If not grazed, browsed, or burnt, it typically reverts to a dense thorn forest 9. Tropical Deciduous Forest N Hot lowlands N Most trees are deciduous N Rich soil 10. Tropical Evergreen Forest N Highest species rich of all biomes N Most nutrients are tied up with vegetation - soil is poor 52.4 What is a Biogeographic Region? N Biogeography - the scientific study of the patterns of distribution of populations, species, and ecological communities N Biogeographic regions are based on the taxonomic composition of the organisms living in them N The biotas of biogeographic regions differ because oceans, mountains, deserts, and other barriers restrict the dispersal of organisms between them. N A species found only within a certain region is said to be endemic to the region N Three advances changed the field of biogeography: 1. Continental Drift N Alfred Wegener proposed this in 1912 (continents moved due to plate tectonics) N 280 million years ago, one land mass was present Pangaea N As continents split, evolution occured at different levels N However, some ancestry was present on Pangaea itself, thus accounting for similar species in various biogeographic regions 2. Phylogenetic Taxonomy N Biogeographers transformed phylogenetic taxonomy trees into Area phylogenies by replacing the names of the taxa with where they were found N This allowed the tracking of dispersal and speciation 3. Island biogeography N Developed by Robert MacArthur and Edward O. Wilson to help explain why oceanic islands always have fewer species than a mainland area of equivalent size N Immigration of new species v. Extinction of species (assumption: no speciation occured when accounting for data) N As species arrive from the species pool into the island, the arrival rate decreases when ultimately the difference between species pool and island = 0. N Extinction rates increase as new species enter the island due to biotic and abiotic factors. www.notesolution.com N @ZZ}7 ]L}]L7 ZL]o]]K~Z9>Zo][Z9]L ]o N Due to the limitZ} Z7]Z]o]]K]ZZZ]]LL7][oo}L back - thus maintaining a certain number of species on the island (usually less than mainland due to the abundance of resources) N This model can also be used to predict how species richness differs among islands of different sizes (island large and close to mainland would have lower extinction rates and higher immigration rates - therefore more species; island small and far would have the least) N The most important contribution of the theory is that biogeography could have an experimental component N Vicariant Event - no individuals disperse but are separated by a barrier and then evolve into different populations o Can be analyzed via observing a clade o If the inference is correct, other clades can be affected similarly o Differences though may indicate different responses to the vicariant, or different dispersal stories N Biotic Interchange - when land masses fuse and dispersal occurs N Dispersion, Vicariance, or Biotic Interchange? Pick the most parsimonious one - the one that requires the least number of unobserved events (Vicariant and dispersion) to account for it 52.5 How is Life Distributed in Aquatic Environments? N Oceans may be connected but water temperatures, salinity, and food supplies all change spatially N Where currents meet, the salinity and temperatures change abruptly N Deep ocean water is a barrier to shallow ocean water - dispersion can occur but is limited to the time it takes for larvae to hatch N Freshw
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