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Chapter 2

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Department
Biology
Course
BIOLOGY 2F03
Professor
Dr
Semester
Fall

Description
Chapter 2: bio 2fo3 Natural history: is the study of how organisms in a particular area are influenced by factors such as climate, soils, predators, competitors, mutualists and evolutionary history Guanacaste tree- produces disk shaped fruit , it produces a lot of fruit , require large herbivores like camels and horses to disperse their seeds Life on Land and Terrestrial Biomes Why are terrestrial organisms in threat of dehydration?  Most terrestrial organisms are themselves filled with water but find their bodies surrounded by dry air  *therefore, they are at constant threat of dehydration due to evaporation of the water contained within their tissues  Even when an organism can keep their water inside, low temperatures make that water dangerous  When ice crystals form, they can puncture and destroy living cells, leading to organ damage and even death  Heat is also a challenge for terrestrial organisms  At high temperatures , protein denature reducing the efficiency of many biological processes -Compared to aquatic organisms, there is no natural buoyancy for organisms that live on land , having to deal with these new stressors requires specific traits , such as woody tissues in plants , the ability to sweat or pant for some mammals Biomes: major divisions of the terrestrial environment - biomes are distinguished primarily by commonly observed plant species and each is associated with a particular climate Concepts: Large-scale patterns of climatic variation:  Uneven heating of the earth’s spherical surfaces by the sun and the tilt of the earth on its axis combine to produce predictable latitudinal variation in climate o Average temperatures are lower and more seasonal at middle and high lattidues than near the equator o Deserts, wwhich are in a narrow band of latitudes around the globe, receive little precipitation which generally falls unpredictably in time and space o Temperature, Precipiation, and Atmospheric Circulation What is most of earth’s climatic variation caused by?  Caused by uneven heating of its surface by the sun  This uneven heating results from the spherical shape of the earth and the angle at which the earth rotates on its axis as it orbits the sun  Because earth is a sphere, the sun’s rays are more concentrated where the sun is diretly overhead Why do seasons occur?  Because earth is tilted at 23.5* away from perpendicular  Therefore the amount of sun received by the northern and southern hemisphere change seasonally What happens during northern summer hemisphere?  Is tilted toward the sun during northern summer and receives more solar energy than southern hemisphere What happens during northern winter?  The northern hemisphere is titled away from the sun and the southern hemsihere receives mor solar energy  The sun is overhead the equator during spring and autummal equinoxes on March 21, and sept 23  On march 21, and sept 23, both hemispheres (northern and southern ) revieve equal amounts of sunlight What happens on northern summer solstice?  On june 21 , northern hemisphere recives more sunlight  The sun is directly overhead at the tropic of cancer , at 23.5* N latitutude , What happens during northern winter solstice? st  On December 21  Sun is directly overhead at the tropic of Capricorn at 23.5* S latitude What produces spatial and temporal variation in precipaiton?  Heating of the earth’s surface and atmosphere drives circulation of the atmosphere and influences patterns of precipitation  The sun heats air at the equator , causeing air to expand rise , . Warm moist air cools as it rises , and since cool air holds less water vp ,the water vapor condenses and forms clouds How is Hadley cell formed?  As air mass moves away from equator , it cools, which increases its density  Eventually, it sinks back to earth’s surface at about 30* lattidue  Air moving from 30* latitude back to the equator completes a thermal loop which forms a Hadley cell What are the 3 atmospheric cells on either side of the equator?  Hadley cell  Ferrel cell  Polar cells Describe Polar cells?  Similar to Hadley cell, driven by air movement associated with warming at 60* latitude and cooling at poles  It is primarily responsible for the weather patterns associated with most northerly and southerly areas, bringing cool weather from the poles Describe Ferrel Cell?  Occurs at midlatiudes and is driven in part by the effects of the Hadley and Polar cells (because it is in the middle of polar and Hadley cells)  When moist air flowing from the Hadley cell rises as it meets cold air flowing from the polar cell. Moisture picked up from desert regions at lower latitudes condenses to form the clouds that produce the abundant precipitation of temperature regions What direction is air movement?  It is from north to south What direction does earth rotate> - west to east What are northeast and southeast trade winds?  Winds that blow from the northeast in the northern hemisphere and from the south east in the southern hemisphere What are the westerlies?  Winds that blow mainly from the west, between 30* and 60* , within the template belt , of template latitudes What are polar easterlies?  Winds that blow from the east at high latitudes What is coriolis effect?  Because of the coreiolic effect, winds don’t directly flow from north to south direction  In the northern hemisphere, the coriolois effect causes an apparent deflection of winds to the right of their direction of travel and to the left in the southern hemisphere Climate diagrams: developed by Henrich Walter , as a tool to explore the relationship between the distribution of terrestrial vegetation and climate - summarize useful climatic info, including seasonal variation in temp and preciptaion, the length and intensity of wet and dry seasons, and the portion of the year during which average min temp is above and below 0* - For southern hemisphere, starts from July and ends with -for northern hemisphere begins with January and ends with December Why are temp and precipitation on different scales? -Temp and precipitation are plotted on different scales so that 10* C equals 20 mm of preicpation , so that the relative positions of temp and prep lines reflect water availability  When precipitation line is above temp line , adequate moisture for platn growth exists , moist periods  When temp lines are bove the precipitation line , evaporation exceeds precipation and , dry periods occur  Moist periods are sep by months of may to sept when the temp line rises above the precipitation line , indicating drought 2.2: Soil: Foundation of terrestrial Biomes What is soil: it is a complex mixture of living and nonliving material upon which most terrestrial life depends  Soil structure results from the long-term interaction of climate, organisms, topography and parent mineral material Describe the layers of the soil  At the surface of the soil lies the majority of the organic matter like leave, twigs, flowers, and fruits  In Canada, this organic horizon is called either the O or the LFH horizon o O Horizons  Found in soils in which plant materials is primarily aquatic in nature ex) peat mosses o LFH Horizons  Are found in most upland sites  Upper layer of LFH horizon contains loose, fragmented plant litter  Small organic horizons are found in areas with little litter deposition ( ex, deserts, and farmland), or high decomposition rates  Deep organic horizons are found in areas with substantial litter inputs andéor low decomposition rates ( ex bogs and fens )  A horizon o Contains mixture of mineral materials like clay, slit and sand and organic material derived from organic horizon from above o Supports biological activities like burrowing animals such as earthwarms , which can mix organic matter from the organic horizon into the A horizon o Is richer in mineral nutrients o Leached of clays, iron, aluminum, silicates and humus (partially decomposed organic matter) which all move into the B horizon  B Horizon o Contains materials leached from above so from A horizon o Forms a banding pattern  C horizon o Consists of weathered parent material, which has been broken down through the actions of frost, water , microbial activity and deep penetrating roots o This weathering results in production of sand, slit, clay and rock fragments o Under the C horizon there is unweathered parent material like bedrock 2.3: Natural Histroy and Geography of Biomes  The geographic disticbution ofterrestrial biomes corresponds closely to variation in climate, espically prevailing temp and precipitation How many biomes are there?  9 Describe Tundra biome?  In northern areas  Open landscape of mosses, lichens, dwarf willows, dotted with small ponds, and laced with clear streams  Geography: o North of the arctic circle o Scanadavia, across northern European Russia, through northern siberai and across northern Alaska and cananada , and small amounts of Greenland  Cliamte: o Cold and dry o But doesn’t get quiete as cold in the winter or quite as warm in the summer as Boreal does o Short summers in the northern tundra therefore soggy , and ponds and streams o Precipitation varies from less than 200 mm- 699 nn o Precipitation exceeds evaporation  Soils: o Soil building is slow in the cold tundra , and therefore there are deposits of peat and humus o Underlain by a layer of permafrost (frozen layer of soil that remains frozen o Solifuction: process that slowly moves soils down slopes o Net like pattern on surface of tundra soils  Biology : o Dominated by patchwork of perennial herbaceous platns, especially grasses, sedges , mosses and lichens , eaten by reinder and caribou o Plants are short, with long strong stems ,can withstand strong winds o In the north of the thundra, the sun will never set during the summer and so plants are able to photsyntheisze continuously o One of the last biomes , that supports large native mammals like reindeer, caribou, musk ox, bear, and wolves o Small mammals like arctic fox, lemming, weasel, and ground squirrel are also abundant , owls are also present o Insects are not diverse  Human influences: o Before there were mainly hunters, o Now humans go therefore ; oil extraction, exploration, natural gas, variety of minerals like diamonds, Describe Boreal Forest  Also known as Taiga  Contains wood and water that covers over 11% of earth’s land  Extends around the globe, in a repeating pattern: forest-water, forest-water  The summer forest is coloured green, gray , and brown , and the long northern winter turns the breal forest into a land of white solitude Geography:  Are in Northern Hemisphere  Extend from Scandinavia through European Russia across Siberia to central Alaska, and across central Canada  These forests are bounded in the south either by temperate forests or temperate grasslands and in the north by tundra Climate  Found where winters are usually longer than 6 months and the summers too short to support temperate forests  Found in some of the most variable climates on earth  Precipitation in boreal forest is moderate , ranging from about 200-600 mm  Low temp and long winters and therefore, evaporation rates are low and drought is either infrequent or brief  When droughts occur, forest fires can burn vast areas of boreal forest Soils  Boreal forest soils tend to be low fertility, thin, and acidic  Low temperatures and low pH slow down decomposition of plant litter and the rate of soil building  As a consequence, nutrients are largely tied up in a thick layer of plant litter that carpets the forest floor Biology  Dominated by evergreen conifers such as spruce, fir and pines  Along the base of most trees is a carpet of mosses and other non-vascular plants  These plants trap most of the rainfall and are home to a lot of organisms  Plants of boreal are adapted to cold winters and low nutrient availability  A characteristic of all forests , including boreal is step vertical gradient in light  Dominated by moss species but also have bogs anf fens  Boreal forest is home to mnay animals , winter home of migratory caribou and reindeer and the yar round home of moose and woodland bison  Lynx, wolverine, snowshoe h
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