Transcript Deserts, Tundra, Grasslands, Forests

Chapter 7, 8 and 9 (pgs 110-153)
 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.
 Pavement: the
lower level of soil that
becomes exposed as loose soil is
removed (blown away by wind)
• Composed of hard-baked sand and rock
• Prevents the washing away of soil
2
Main Types of Deserts (in U.S.)
 Cool
Deserts
• Sierra Nevada and Rocky Mountains
 Hot
Deserts
• Southwest (Arizona, New Mexico, Texas)
 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.
 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 roots
 Shallow roots growing over wide area
allow maximum absorption of water.
 Desert
Animals
• Get water they need from their food.
• Able to store water.
• Compact bodies.
• Insects and Reptiles
 Outer coating to reduce water loss.
• Nocturnal: animals that are active at night and
sleep during the day.
 Most desert animals are nocturnal.
1.
2.
3.
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?
 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.
 Desertification
• The 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!!
1.
2.
How do semiarid regions differ from
deserts?
Explain the role of mountains in the
formation of deserts.
 Location
• Northern Hemisphere, south of polar ice caps.
• Cover 10% of Earth’s surface.
• Largest biome.
 Climate
• Less 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.

Tundra Plants
• Small and grow close to the
ground.
• Roots close to surface.
• Permafrost prevents deep
roots and large plants.
• Trees are much smaller
(willow, birch).
**Plants grow very slowly, so
destruction by humans is
devastating

Tundra Animals
• Seasonal visitors
 Migration: long-distance seasonal
travel.
 Caribou, migratory birds, Arctic
wolf.
• Thick coats, hairs filled with air
(insulation).
 Grassland: 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 Climate
• Wetter than deserts.
• Desert-grassland boundary: the area between
deserts and grasslands where increased rainfall
enables some grasses to grow.
 Grassland
Organisms
• Grass!
 Most of the grass plant is underground-not limited by
rain and fires.
• Fire
 Keep grass from over growing the world.
 Burn away layer of dead grass.
 Release nutrients.
 Allow germination of grass seeds.
• Some plants are drought-resistant.
• Grazing animals
 Bison!
 Keep vegetation close to ground.
 Aerate the soil (prairie dogs, earthworms, etc).
 Rainy
seasons and drought seasons.
• Determine what kinds of organisms live here.
 Divided
into:
• Steppe
• Prairie
• Savanna
1.
2.
Where are grasslands located in relation
to deserts and forests?
Identify some biotic and abiotic factors
affecting the growth of grasslands.
 Steppes: 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.
 Steppe
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.
 Steppe
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.
 Animals
• Migrate, hibernate, burrow underground.
1.
2.
How does the activity of burrowing
animals benefit the prairie?
Name some ways in which steppes and
prairies are damaged and desertification
develops.
 Savannas: tropical
grasslands ranging
from dry scrubland to wet, open
woodland.
 Asia, Africa, South America
 Savanna Climate
• Rainy Seasons followed by drought
 150 cm of rain per year from January to April.
 Savanna
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.
• Many 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.
1.
2.
3.
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?
 Northern
Hemisphere
 Warm summer, 2-5 months.
 Long, cold winters.
 40-200 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.
• Examples: pines, hemlock, fir, spruce, cedar.
 Soil
poor and acidic.
 Snow fall traps heat and prevents ground
from freezing solid.
• Protects tree roots
 Small
herbivores eat seeds
• Mice, squirrels, jays, insects, etc.
 Large
herbivores eat plants and bark
• Elk, moose, beavers, snowshoe hares.
1.
What does the word coniferous mean?
 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.
 Examples: 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.
 Falling
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.
1.
Why is the soil of a deciduous forest more
fertile than that of a coniferous forest?
 Temperatures
about 25 Celsius all year.
 Growing season can last 12 months.
 100-450 cm of rainfall per year.
 Rainforest
Structure
• Rain 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 50-60 meters.
 Canopy captures 99% sunlight.
• Sparse vegetation on forest floor.
• Almost all nutrients contained in living
organisms.
• Topsoil thin, poor in nutrients.
 Organic matter consumed so quickly by other
organisms.
• Thin tree roots.
 Organisms
and Diversity
• Due to:
 Diversity of rain forest plants.
 Wide variety of habitats.
 Deforestation
• Destruction of forest as a result of human activity.
• Need for space and wood = driving force.
1.
2.
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.