Biology 2483A Study Guide - Final Guide: Tropical Rainforest, Biome, Soil Fertility

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Published on 15 Dec 2017
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Unit 1: Organisms and their Environment
Chapter 3: The Biosphere
Biosphere: zone of life on Earth
oDifferent combinations of climate (moisture availability and temperature) has effects
oSandwiched between the lithosphere (Earth’s surface crust and upper mantle) and the troposphere
(lowest layer of the atmosphere)
Biomes: large-scale biological communities shaped by the physical environment particularly climate
oCategorized by dominant plant forms, not taxonomic relationships
Plants occupy sites for a long time and are good indicators of the physical environment, reflecting climatic
conditions and disturbances (*so are some microorganisms but their size are a downfall)
oAnimals can migrate to avoid exposure to adverse environmental conditions
Terrestrial biomes are characterized by growth forms of the dominant plants & their leaf traits
odeciduousness (seasonal shedding of leaves) or
osucculence (development of fleshy water storage tissues e.g. cactus)
Plant Growth Forms and their Environment
Plant growth forms represent an evolutionary response to the environment, particularly climate and soil fertility
(Sclerophyllous shrubs are often characterized by their leathery leaf texture)
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oReminder that Convergence: evolution of similar growth forms among distantly related species in
response to similar selection pressures
Similar growth forms can be found on different continents, even though plants are not
genetically related
Temperature has direct physiological effects on plant growth form (plants can over heat/ freeze)
Precipitation and temperature act together to influence water availability and water loss by plants (can go into
water stress)
Water availability and soil temperature determine the supply of nutrients in the soil (affects micro-absorption)
Biomes vary with mean annual temperature and precipitation but does not account for seasonal variation
(*Triangle is formed when nine terrestrial biomes are plotted)
oNote for example, not all deserts are hot  dryness defines this biome
oAlso, some info is lost looking at mean values because smaller biomes such as the grasslands may be
more present in the graph if seasons were accounted for
Global Biome Distributions
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oThe biomes are becoming altered and history of biomes has changed
Human land use: conversion of land to agriculture, logging, resource extraction, urban
development
Growing human population e.g. London Ontario no longer “The Forest City”
oThe potential and actual distributions of biomes are markedly different
Global biome distributions are affected by human activities
oMore heavily populated areas have a much larger impact on natural biomes (effect is regional)
Climate diagrams: show characteristic seasonal patterns of temperature and precipitation at a representative
location (should be able to recognize each one for each main biome)
oBlue areas on climate diagram: temperatures below freezing for extended periods
oYellow areas: precipitation curve falls below temp –not enough water for plant growth
The Nine Major Terrestrial Biomes
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