Biological Foundations 112, Lecture 35


Biomes

Chapter 46, pages 1073-1081
Biomes 1
Biomes 2


I.   Ecology - The study of living organisms, their relationships to one another and to the            
                      environment

II.  Organization of the living world

      A.   Biosphere

             1.   Portion of the earth that supports life

             2.   Floor of the ocean to the top of the highest mountain

                   a.   36,000 feet below the ocean surface is the deepest part of the ocean

                   b.   30,000 feet above the ocean surface is the highest mountain

             3.   Life is scarce at the extremes of the biosphere

                   a.   Most of life is in a narrow band around the earth

                   b.   100-300 feet in water to where light penetrates

                   c.   Timberline on terrestrial habitats (about 15,000 feet)

                   d.   99% of life exists in about a 3 mile band (approximately 5,000 feet per mile)      
                         around the earth

                   e.   The earth is about 8,000 miles in diameter

                   f.   Thus life exists in about 3/8000ths of the earth's diameter

             4.   Three distinct parts to the biosphere:

                   a.   Atmosphere - gaseous envelope

                   b.   Hydrosphere - water

                   c.   Lithosphere - rocks and earth

             5.   The energy necessary for life comes from the sun

             6.   The chemicals necessary for life come from the air, water, soil

             7.   The earth is a closed system:  all things necessary for life except the sun comes      
                   from within the earth, nothing comes from outside the earth

III. Subdivisions of the biosphere

      A.   Aquatic Habitats - water habitats of the earth

      B.   Biomes - terrestrial habitats of the earth

            1.   Very large terrestrial regions of the earth characterized by:

                  a.   Climate - precipitation and temperature

                  b.   Vegetation

                  c.   Animal life

                  d.   General soil type

            2.   There are about a dozen biomes of which we will study about nine

     C.   Biome groupings

            1.   The Boreal Biomes

                  a.   General characteristics

                        (1)  Generally circumpolar

                        (2)  Generally in the far north

                        (3)   Extends southward along the high mountain tops

                  b.  Tundra Biome

                  c.  Boreal Forest Biome

                  d.  Temperate Coniferous Forest Biome

            2.   The Temperate Biomes

                  a.   General Characteristics

                        (1)  Exists below the boreal forests

                        (2)  Are not circumpolar nor evenly distributed because they are influenced by    
                               precipitation

                        (3)  Rainfall varies greatly with longitude (as one moves from west to east)

                        (4)  Various physical features of the environment modify the amount of rainfall a  
                               given region receives

                  b.   Deciduous Forest Biome

                  c.   Temperate Grasslands Biome

                  d.   Chaparral Biome

                  e.   Desert Biome

            3.   Tropical Biomes

                  a.   General Characteristics

                        (1)  Determined mainly by the amount of precipitation

                        (2)  Includes grasslands and deserts as well as forests

                        (3)  Seasonal distribution of rainfall is also as important as the amount

                        (4)  Mineral-poor soil leached by heavy precipitation with little or no organic      
                               material in it

                        (5)  Still very productive - most of the nutrients in this ecosystem are tied up in    
                                                                the vegetation

                  b.   Tropical Rainforest Biome

                  c.   Savannah Biome

     D.   Discussion of each biome

            1.   Tundra Biome (tundra)

                  a.   Location

                        (1)  Far north where ever the snow melts seasonally

                        (2)  Circumpolar

                        (3)  Does not exist in the Southern Hemisphere because there is no land in the    
                               proper latitudes

                        (4)  Extends south along the highest mountain tops and exists as the regions        
                               above timberline

                  b.   Physical characteristics

                        (1)  Swampy landscape of broad shallow lakes, sluggish streams, and bogs

                        (2)  Permafrost - the permanently frozen ground below the upper part that        
                                                     thaws seasonally

                               (a)  Interferes with drainage

                               (b)  If too near the surface, plants can't get any roots down in the soil

                        (3)  Some have very little rainfall and thus are arctic deserts

                  c.   Species diversity

                        (1)  Growing season very short

                        (2)  Low species diversity

                              (a)  Large numbers of individuals

                              (b)  Low numbers of different species

                              (c)  Dominated by reindeer moss (a lichen), other perennial grasses, sedges,
                                    and annuals

                              (d)  No shrubs or trees

                              (e)  Animals such as:  lemmings, weasels, arctic foxes, snowshoe hares,        
                                                               ptarmigan, snowy owls, hawks, musk-oxen, caribou,
                                                               and reindeer

                  d.   Regenerates very slowly because of the low rates of photosynthesis

                        (1)  Military use and oil exploration have caused great damage to tundra

                        (2)  May take hundreds of years to heal

            2.   Boreal Forest Biome (boreal forest)

                  a.   Location

                        (1)  Circumpolar

                        (2)  Dominated by coniferous forests in the far north just below the tundra biome

                        (3)  Extends south into the highest mountain tops and comprises the timberline    
                              tree species

                  b.   Physical characteristics

                        (1)  Permafrost usually absent

                        (2)  Deeper and better soil than tundra biome

                        (3)  Soil is acid and mineral-poor because of the acid produced by decomposing
                               needles

                  c.   Species diversity

                        (1)  Growing season longer than the tundra biome but still short

                        (2)  Conifers clearly dominate

                        (3)  Can have aspen or birch as successional trees in logged or burned areas

                        (4)  These plants have a hard time getting water from the soil because of the cold
                               or frozen conditions of the soil particularly in the winter when the soil is        
                               frozen

                        (5)  Animals:  caribou, wolves, bear, moose, rabbits, lynx, sable, and fisher

                        (6)  Most birds migrate into the area in the summer and out of the area in the      
                              winter

                  d.   Line between Tundra Biome and Boreal Forest Biome

                        (1)  Hard line to draw

                        (2)  Southern most tundra biome is interspersed with patches of evergreen forest
                              where the permafrost is locally absent or deeply buried

                        (3)  Muskeg - waterlogged soil that is many times a peat bog where black        
                                                spruce will grow

                  e.   Timberline

                        (1)  At timberline the trees are stunted and distorted because of the harsh            
                               environment

                        (2)  Krummholz - the stunted miniature forest at this elevation where the trees    
                                                     are flagged

            3.   Temperate Coniferous Forest Biome (temperate coniferous forest biome)

                  a.   Location

                        (1)  Temperate regions of North America, mainly in the west.  The best              
                               examples are in Washington, Oregon, and Northern California

                        (2)  Gets large amounts of winter rainfall and drought during the summer

                        (3)  Exists as the upper middle elevations of coniferous forests in California

                        (4)  Essentially the coniferous forest just below timberline in California

                  b.   Physical Characteristics

                        (1)  Mainly tall (100-200 foot) coniferous trees

                        (2)  Temperate Rain Forest exists along the Olympic Peninsula in Washington
                               State and up the coastal regions of British Columbia and Alaska

                               (a)  Has very high rainfall

                               (b)  Similar in structure to a tropical rain forest biome with equivalent types  
                                      of species

                               (c)  Nutrient-poor soils

                        (3)   Generally plenty of minerals in the soils but the soils aren't well developed

                  c.   Species diversity amounts to about a dozen conifers and a number of different    
                        species of animals

            4.   Deciduous Forest Biome (deciduous forest biome)

                  a.   Location - Europe, Asia, and Eastern U.S.

                  b.   Physical characteristics

                        (1)  Precipitation is from 70 to 150 cm annually

                        (2)  Dominated by broadleaved hardwood trees

                        (3)  Loose leaves in fall

                        (4)  Broadleaved evergreens increase and broadleaved deciduous trees              
                              decrease as one moves south

                        (5)  Good deep soils that are good for agriculture

                               (a)  Among the first biomes to be converted to agriculture by the pioneers

                               (b)  No substantial loss in fertility of the soil over the years of agricultural use
                                      even in Europe

                  c.   Species divesity

                        (1)  Good species diversity

                        (2)  Animals - puma, wolves, deer, bison, bears, plus other animals and birds

                        (3)  Plants - mostly broadleaved deciduous hardwoods

            5.   Temperate Grassland Biome (temperate grassland biome)

                  a.   Location

                        (1)  Typical of the North American midwest

                        (2)  Other parts of the world such as the Ukraine

                  b.   Physical characteristics

                        (1)  Few trees except those that are riparian

                        (2)  Burned frequently by indians which discourages forests and encourages        
                               grasslands

                        (3)  Thus areas of grasslands

                        (4)  Soils very good rich and deep, held together by the mat of roots from the    
                               grassland

                        (5)  Less rainfall here than the deciduous forests

                        (6)  The mass of roots made it hard for the wooden plow to turn over the soil    
                               but the tractor and steel plow has changed all that

                        (7)  Little now exists because of its usefulness for agriculture

                        (8)  Of all the biomes, this biome has the best soils

                  c.   Species diversity

                        (1)  Originally tall grasses grew here

                        (2)  Bison roamed the prairie

                        (3)  Other animals - wolves, coyotes, prairie dogs, foxes, black-footed ferrets,  
                                                       various hawks, grouse, snakes, lizards, and insects

                  d.   Subdivisions

                        (1)  Tall Grass Prairie - the prairies described above

                        (2)  Steppes

                               (a)  Short grass prairies

                               (b)  Greater precipitation than the deserts and less precipitation than            
                                      the tall grass prairies

                               (c)  Shallower soil than the tall grass prairie

                               (d)  Mostly bunch grasses with bare soil between

                               (e)  Drought and overgrazing have destroyed these in the U.S. and other      
                                     places in the world

            6.   Chaparral Biome (chaparral)

                  a.   Physical characteristics

                        (1)  Brushy areas composed of shrubs

                        (2)  Mild winters and very dry summers

                        (3)  Typical Mediterranean climate

                        (4)  During the rainy season the habitat will be lush and green but will soon turn  
                              dry and brown when summer comes

                        (5)  Sclerophyllous leaves

                               (a)  Hard, small, and leathery leaves

                               (b)  These type of leaves resist water loss and wilting

                        (6)  Frequent fires occur in chaparral so species are fire-adapted

                  b.   Location - California, Mediterranean region, and Australia

                  c.   Species diversity

                        (1)  Medium amount of different species

                        (2)  Dominated by shrubs

                        (3)  May contain drought-resistant pines or oak trees

            7.   Desert Biome (desert biome)

                  a.   Physical characteristics

                        (1)  Arid areas

                        (2)  Sparse to no vegetation

                        (3)  Low water content of the environment leads to temperature extremes of hot
                               and cold in one day, up to 100o F in one day

                        (4)  Vegetation varies greatly depending upon the amount of rainfall

                               (a)  5 inches per year produces deserts like exist in southern California with
                                     cactus, yucca, and Joshua trees

                               (b)  0 to less than 5 inches per year with no rainfall in some years produces  
                                     deserts like the Sahara where there is little or no vegetation at all

                  b.   Species diversity

                        (1)  Small rodents like the kangaroo rat, lizards, snakes, jackrabbits, and desert  
                               bighorn sheep

                        (2)  Plant life very well adapted for a dry environment

                               (a)  Reduced or no leaves at all

                               (b)  Stomata open at night

                               (c)  Allelopathy is best exhibited in desert plants (growth inhibiting              
                                     chemicals produced by plants to keep other plants from growing            
                                     too close)

                               (d)  Thorns and spines are present on plants to keep animals from eating      
                                      them

                               (e)  Water storage tissue is typical in desert plants

                  c.   Some deserts are so dry that virtually no plant life occurs in them

                        (1)  African Namib Desert

                        (2)  Atacama-Sechura Desert of Chile and Peru

                               (a)  Coastal desert

                               (b)  Fog from the ocean provides moisture

                               (c)  Animals emerge at night or in early morning and lick moisture produced
                                     by fog from coats

                               (d)  Plants absorb moisture from leaves

            8.   Tropical Rainforest Biome (tropical rainforest biome)

                  a.   Species diversity

                        (1)   Greatest amount of species diversity of all the terrestrial habitats

                        (2)  No one species dominates

                        (3)  In a quarter of a mile it is possible to see all different tree species with no      
                               two of the same species

                        (4)  Mostly evergreen broadleaved trees in these forests

                               (a)  These trees have shallow roots so to get minerals from decaying leaves

                               (b)  Thus poor anchorage of these trees

                               (c)  These trees have swollen bases (buttresses) to help hold them up

                        (5)  Ants are prominent in the tropical rain forest biome

                               (a)  Need no sunlight to keep them warm in the tropics

                               (b)  Thus they nest and rove everywhere

                               (c)  Some have developed a symbiotic relationship with Acacia trees and    
                                     shrubs

                        (6)  Animal species - insect, reptile, amphibian fauna, birds, and mammals

                  b.   Physical characteristics

                        (1)  Vegetation is not dense at ground level in a mature forest

                        (2)  Vegetation is very dense in areas recovering from logging, fire, agricultural    
                               use, or near streams

                        (3)  Continuous canopy produces a dark habitat with an extremely humid            
                               microclimate

                        (4)  Much of  the precipitation is locally recycled water coming from                  
                               transpiration of the forest's own trees.  Thus, if the forest is removed it        
                               may be hard to reestablish the forest.

                        (5)  Three distinct stories

                               (a)  Canopy story - crowns of the tallest trees

                               (b)  Middle story - continuous canopy of leaves that produces the humid    
                                                              environment below

                               (c)  Understory - plants specialized for life in constant shade as well as      
                                                            seedlings of canopy and middle story trees

                        (6)  All stories support extensive epiphytic communities.  These epiphytic            
                               communities can be so extensive as to interfere with photosynthesis and      
                               can break limbs

                        (7)  Most mineral cycling occurs among the epiphytes and the growing leaves of  
                               the forest canopy

                        (8)  Vines as thick as a man's thigh abound

                               (a)  Strangler tree is an example

                               (b)  Overgrows the trunk of the host, eventually killing it

                  c.   Epiphytes

                        (1)  Rain tends to run off the host tree branches immediately leaving xerophytic  
                               condiditons for many epiphytes

                        (2)  Cacti make good epiphytes under these conditions

                        (3)  Staghorn ferns possess specialized leaves that retain pockets of spongy soil  
                               that absorb water

                        (4)  Orchids have specialized spongy tissues surrounding their roots that store    
                               water and harbor cyanobacteria for nitrogen fixing

                        (5)  Bromeliads store as much as a gallon of rainwater in their leaf cups

                               (a)  Mosquito larvae and other insects live in these aerial swamps

                               (b)  Quite a diversity of life!

                  d.   High temperature decomposes organic material in the detritus food chain very    
                        rapidly

            9.   Savannah Biome (savannah biome)

                  a.   Savannah (veld) is a tropical grassland or very open woodland

                  b.   Widely spaced trees like Acacia (with thorns) grow amid tall grasses

                  c.   Greatest herbivore biomass occurs in the African savannah - antelope, giraffe,
                        zebra, lions, hyenas, etc.

                  d.   The Savannah Biome is maintained by either low annual rainfall or seasonal        
                         rainfall

                  e.   Thus the herds of animals may migrate during these times

                  f.    This biome is rapidly being converted to range land for cattle and other animals  
                        which produces severe over-grazing

     


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