ENVIRON 102 Chapter Notes - Chapter 10: Northern Hemisphere, Growing Season, Overgrazing
10 May 2018
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Chapter 10 Geography of Terrestrial Life (all)
10.1 Terrestrial Biomes and Climate
Convergent evolution: notion that similar selective pressures will produce organisms with similar
traits even if there is no close genetic relationship
Biomes: communities of similar organisms found in a particular climate
o Tropical, temperate, and polar
o Defined by latitude and atmospheric circulation
Tropical zone: equator, 25 degrees north and south, Hadley wind cells
o Tropical rain forest, tropical seasonal forest, and tropical savanna
Temperate zone: between 25 and 60 degrees north and south, Ferrel wind cells
o Temperate deciduous forest, temperate evergreen forest, chaparral, and grassland
Polar zone: above 60 degrees latitude north and south, polar wind cells
o Boreal forest and tundra
Desert biomes = in dry areas of these three zones
Factors that influence distribution of biomes:
o Mountain ranges
o Proximity to water
o Annual precipitation and rate of evaporation (determined by temperatures)
o Seasonal variations in temperature
o Soil and fire
Continental climates: areas far away from large bodies of water (large variation in temperatures)
Maritime climates: lands near oceans or large lakes (less variation)
Most biomes fall in the triangular area between cold and dry, warm and dry, and warm and wet
o Cold and wet is rare because cold air cannot hold much moisture
Climatograph: graph that shows the pattern of seasonal changes in temperature and precipitation
for a particular location
o X axis = month; y axis = average temperature and precipitation
o Availability of moisture can be inferred by comparing temperature and precipitation
o When evaporation > precipitation => lack of water
10.2 Tropical Biomes
Tropical Rain Forest
Annual rainfall is greater than 2000 mm year-round
Enormous diversity of plants and animals
o Most animal species than any other biome (mostly insects)
o Diversity = discovery of medicines and pest-resistant food crops
Vertical arrangement of foliage in rain forest – understory, midstory, canopy, and emergents
Canopy of evergreen trees that allow little light to poke through
Highest net primary production due to rapid recycling of nutrients (via decomposition)
High degree of endemism: many species thrive within very restricted geographic ranges
Threatened by deforestation
o High endemism causes many species to go extinct because of deforestation
o Nutrient cycle disrupted
o Erosion of topsoil crop failure
o Reduces ability to take up and store carbon increase in greenhouse gases
o Poverty in tropical zone countries encourages deforestation
Tropical Seasonal Forest
23 degrees north and south of equator
Wet regions – forests with canopy trees; dry regions – scrubby woodlands
find more resources at oneclass.com
find more resources at oneclass.com
Plants thrive during rainy season, but organisms also adapt to drought
During dry season, trees lose leaves to reduce need for water = DROUGHT DECIDUOUS trees
Also face threat of deforestation and transforming the land to agricultural sites
o Disrupt migration for animals
Tropical Savanna
Rainfall is highly seasonal
Drought conditions persist for more than half a year = seasonal moisture deficits
Open grasslands and few scattered trees
o Most trees are drought deciduous
o Scarcity of trees due to grazing of large herds of animals, fires, and drought
o Not a lot of trees plenty of light for the ground grassland
During dry seasons, animals migrate to food and water
Debate about whether humans have been creating more and more tropical savannas by
domesticating grazing animals and setting fires
10.3 Temperate Biomes
)ncludes over 60% of Earth’s landmass
25 to 60 degrees north and south of equator
Mostly in Asia, Europe, and North America
Average annual temperature is 41 to 68 degrees Fahrenheit; annual precipitation is 8 to 80 inches
Temperate Deciduous Forest
Dominated by mostly broad-leaved trees that lose their leaves in the fall and grow a new set in
spring
Moderate summers and cold winters
Growing season is period between last hard frost and first hard frost in fall
o Growing season: the part of the year during which rainfall and temperature allow plants to
grow
Annual loss and regrowth of trees decomposition of leaves nutrient recycling, addition of
organic matter into soil complex food web
Some bird species migrate between the tropical and temperate zones, stopping by the temperate
deciduous forests in spring and summer
Most temperate deciduous forests are affected by human populations and urban development
o Eastern US – 50-70% of temperate deciduous forests have been cleared out (1700-1900)
o Declining populations of migratory birds
o Susceptible to non-native plant/animal species
Temperate Evergreen Forest
Trees keep leaves on (evergreen)
Less precipitation and warmers temperatures than temperate deciduous forests
Summer is notably drier than winter
Northern Hemisphere conifers (cone-bearing trees ex: pine, spruce, fir)
Woody litter – provide shelter for banana slugs and voles; cavities in old trees/logs – owls and
flying squirrels
Temperate Rain Forest
Evergreen trees
Heavy winter rains and summer fogs give rise to evergreen forests
Usually in coastal regions
Woody litter – provide shelter for banana slugs and voles; cavities in old trees/logs – owls and
flying squirrels
Human impact on temperate evergreen/rain forests
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Convergent evolution: notion that similar selective pressures will produce organisms with similar traits even if there is no close genetic relationship. Biomes: communities of similar organisms found in a particular climate: tropical, temperate, and polar, defined by latitude and atmospheric circulation. Tropical zone: equator, 25 degrees north and south, hadley wind cells: tropical rain forest, tropical seasonal forest, and tropical savanna. Temperate zone: between 25 and 60 degrees north and south, ferrel wind cells: temperate deciduous forest, temperate evergreen forest, chaparral, and grassland. Polar zone: above 60 degrees latitude north and south, polar wind cells: boreal forest and tundra. Desert biomes = in dry areas of these three zones. Factors that influence distribution of biomes: mountain ranges, proximity to water, annual precipitation and rate of evaporation (determined by temperatures, seasonal variations in temperature, soil and fire. Continental climates: areas far away from large bodies of water (large variation in temperatures) Maritime climates: lands near oceans or large lakes (less variation)
