37.1 DESERTS All deserts receive very little rain. Soil rich in minerals; poor in organic material.Lack of rain prevents:Leaching: rainwater moving through soil carries minerals deeper into the soil – washes minerals from topsoil.Not many plants.Slows decay of organic material.Not much topsoil.
4DesertsPavement: the lower level of soil that becomes exposed as loose soil is removed (blown away by wind)Composed of hard-baked sand and rockPrevents the washing away of soil
5Deserts 2 Main Types of Deserts (in U.S.) Cool Deserts Hot Deserts Sierra Nevada and Rocky MountainsHot DesertsSouthwest (Arizona, New Mexico, Texas)
6DESERT CLIMATE Less than 10 cm precipitation per year. Limiting factor for desert biome.Few, short thunderstorms with long, dry periods.Large change in temperature in 24 hours due to dry air.
7DESERT ORGANISMS Desert Plants Able to absorb water from ground and prevent loss from tissues.Cactus:Spines (modified leaves)prevent water loss.Store water in their tissues.Spines protect from predation.Succulents: plants with thick, water- filled tissues.Plant rootsShallow roots growing over wide area allow maximum absorption of water.
8Desert Animals Get water they need from their food. Able to store water.Compact bodies.Insects and ReptilesOuter coating to reduce water loss.Nocturnal: animals that are active at night and sleep during the day.Most desert animals are nocturnal.
9CHECK FOR UNDERSTANDING: What is meant by the pavement of a desert?Explain why desert soil tends to be rich in minerals but poor in organic material.Why are midday temperatures in the summer generally higher in deserts than in forests?
107.2 FORMATION OF DESERTS Natural Desert Formation Dry air flows towards the Earth’s poles.Becomes cooler and sinks towards Earth.Cool, dry air picks up the moisture in the soil and the soil dries out.Called rainshadow effect.
12Africa is being desertified!! DesertificationThe process of changing semiarid land into desert as a result of human activity.Too many animals grazing the land.Too many improper farming techniques.Deserts bordered by semiarid regions.Africa is being desertified!!
13CHECK FOR UNDERSTANDING: How do semiarid regions differ from deserts?Explain the role of mountains in the formation of deserts.
147.3 TUNDRA Location Climate Northern Hemisphere, south of polar ice caps.Cover 10% of Earth’s surface.Largest biome.ClimateLess than 25 cm precipitation per year.Temperatures usually below 10 Celsius.Permafrost: frozen soil below “active zone” (top layer of ground that can thaw in summer).Topsoil insulates so it never thaws.Rainfall during summer does not drain-form bogs that allow breeding of mosquitoes and black flies.
16Tundra Plants Tundra Animals Small and grow close to the ground. Roots close to surface.Permafrost prevents deeproots and large plants.Trees are much smaller(willow, birch).**Plants grow very slowly, sodestruction by humans is devastatingTundra AnimalsSeasonal visitorsMigration: long-distance seasonal travel.Caribou, migratory birds, Arctic wolf.Thick coats, hairs filled with air (insulation).
188.1 GRASSLANDSGrassland: ecosystem in which there is too much water to form a desert, but not enough water to support a forest.Africa, central Asia, South America, Australia.Grassland ClimateWetter than deserts.Desert-grassland boundary: the area between deserts and grasslands where increased rainfall enables some grasses to grow.
19Grassland Organisms Grass! Fire Some plants are drought-resistant. Most of the grass plant is underground-not limited by rain and fires.FireKeep grass from over growing the world.Burn away layer of dead grass.Release nutrients.Allow germination of grass seeds.Some plants are drought-resistant.
20Grazing animals Bison! Keep vegetation close to ground. Aerate the soil (prairie dogs, earthworms, etc).
21Rainy seasons and drought seasons. Divided into: Determine what kinds of organisms live here.Divided into:SteppePrairieSavanna
22CHECK FOR UNDERSTANDING: Where are grasslands located in relation to deserts and forests?Identify some biotic and abiotic factors affecting the growth of grasslands.
238.2 STEPPES AND PRAIRIESSteppes: grasslands of short bunchgrass that get less than 50 cm of rain per year.Located to the west of grasslands (in US).Prairie: grasslands characterized by rolling hills, plains, and sod-forming grasses.
24Steppe and Prairie Climates Steppe-get more than 25 cm, but less than 50 cm of rain per year. Temperature range: -5 Celsius to 30 Celsius.Prairie- 50 cm to 75 cm of rain per year.
25Steppe and Prairie Organisms Sod-forming grasses: grasses that form a mat of soil and roots.Roots prevent soil from drying out and blowing away.Humus: a layer or organic matter formed as the roots of the grasses die. Helps hold water and provide nutrients and food for organisms to grow.Bunchgrasses: short, fine-bladed grasses that grow in a clump.Roots save water, short grass prevents drying out.
27CHECK FOR UNDERSTANDING: How does the activity of burrowing animals benefit the prairie?Name some ways in which steppes and prairies are damaged and desertification develops.
288.3 SAVANNASSavannas: tropical grasslands ranging from dry scrubland to wet, open woodland.Asia, Africa, South AmericaSavanna ClimateRainy Seasons followed by drought150 cm of rain per year from January to April.
30Savanna Organisms Resistant to drought, fires, and grazing animals. Runners: long horizontal stems above or below ground. Used by some plants to reproduce.Tufts: large clumps of tall, coarse grasses.Trees and shrubs have thorns or sharp leaves to protect against grazing.Grow rapidly.
31Many animals reproduce during the rainy season (giraffes, antelopes, elephants). Vertical feeding pattern: animals eat vegetation at different heights. Adaptation to allow animals to make best use of available food with less competition.
32CHECK FOR UNDERSTANDING: What is the purpose of growing runners?How have plants adapted to savanna life?What could happen to the migrating animals in a savanna if they were fenced in a large wildlife park for protection?
349.1 CONIFEROUS FORESTS Northern Hemisphere Warm summer, 2-5 months. Long, cold winters.cm rain per year.Conifers: trees that produce seed cones (coniferous trees).Needle like leaves, covered in waxy substance.Do not lose their “leaves”.Conserve water, shed snow during winter.
35Snow fall traps heat and prevents ground from freezing solid. Examples: pines, hemlock, fir, spruce, cedar.Soil poor and acidic.Snow fall traps heat and prevents ground from freezing solid.Protects tree rootsSmall herbivores eat seedsMice, squirrels, jays, insects, etc.Large herbivores eat plants and barkElk, moose, beavers, snowshoe hares.
36CHECK FOR UNDERSTANDING: What does the word coniferous mean?
379.2 DECIDUOUS FORESTS Temperate zones. Deciduous tree: tree that sheds its leaves during a particular season of the year.Temperatures: -30 Celsius to 30 Celsius.50 – 300 cm rainfall per year, falls regularly.Growing season lasts 6 months.Grow quickly and produce lots of food.Lose leaves and go dormant during autumn.
39Examples: maple, oak, beech, ash, hickory, birch. Canopy: highest layer of deciduous forest.Made of upper branches and leaves of tall trees.Captures most of sunlight.Understory: Next layer of forest; made of trees that are younger and smaller than those of canopy.Shrubs beneath understory.Mosses, ferns, other plants on forest floor.
40Falling leaves decay quickly and add nutrients to soil. Diverse plant and animal life.Humans consume forest-rich soil for farming; trees are good building material.
41CHECK FOR UNDERSTANDING: Why is the soil of a deciduous forest more fertile than that of a coniferous forest?
429.3 RAIN FORESTS Temperatures about 25 Celsius all year. Growing season can last 12 months.cm of rainfall per year.
43Rainforest StructureRain forest: biome with a dense canopy of evergreen, broadleaf trees supported by at lease 200 cm of rain each year.Most diverse and productive biome.Trees (cyprus, balsa, teak, mahogany, etc).Reach heights of meters.Canopy captures 99% sunlight.Sparse vegetation on forest floor.
44Almost all nutrients contained in living organisms. Topsoil thin, poor in nutrients.Organic matter consumed so quickly by other organisms.Thin tree roots.
45Organisms and Diversity Due to:Diversity of rain forest plants.Wide variety of habitats.DeforestationDestruction of forest as a result of human activity.Need for space and wood = driving force.
46CHECK FOR UNDERSTANDING: Why do rainforest trees have buttresses?Plants on the floor of a rain forest often have very large leaves. Propose a hypothesis explaining this observation.