Transcript 6.1.05 Biomes - El Camino College

Chapter 35: The Biosphere
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Climate and the Biosphere
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Climate refers to the prevailing weather
conditions in an area as dictated by
temperature, rainfall, and these factors:
Variations in solar radiation due to a
spherical earth;
The tilt of the earth’s axis as it rotates
about the sun;
Distribution of land masses and oceans;
and
Topography (landscape) features.
Air Circulation
• The earth is a sphere, and thus the sun’s
rays are more direct at the equator and
more spread out at polar regions.
• The tilt of the earth as it orbits the sun
causes one pole or the other to be closer
to the sun, and this accounts for the
occurrence of seasons everywhere on
earth except at the equator.
Distribution of solar energy
Seasons
• Atmospheric heat passes from warm
areas to colder areas.
• Warm, equatorial air rises and moves
toward the poles, creating a zone of lower
pressure that is filled by cold air moving
toward the equator.
• Rotation of the earth modifies air
circulation into three large circulation cells
in each hemisphere.
• As a result, the great deserts occur where
air descends, warms, and becomes very
dry.
Global wind circulation
Effects of Topography
• Topography means the physical features
of the land.
• Mountains effect climate; as air blows up
over a mountain range, it rises and cools,
so the windward side receives more
rainfall than the leeward side.
• The leeward side of mountains is in a rain
shadow and receives considerably less
moisture.
Formation of a rain shadow
• Atmospheric circulations between the
oceans or other large bodies of water and
the landmasses influence regional climate
conditions.
• Oceans are slower to change temperature
than landmasses, thus coastal weather is
unique.
• India has a monsoon climate in which wet
winds blow onshore for half the year.
• In the United States, the Great Lakes
produce lake effect snows.
Biomes of the World
• A biome is a large biogeographical unit of
the biosphere that has a particular mix of
plants and animals that are adapted to
living under certain environmental
conditions.
• Biomes gradually change from one type to
the other, although their distribution can be
predicted by temperature and rainfall.
Pattern of biome distribution
• The distribution of biomes, and thus the
pattern of life on earth, is determined
principally by climate.
• The effect of temperature is seen not only
when we consider latitude but also when
we consider altitude.
• The same sequence of biomes that
appears from equator to the North Pole is
evident when ascending a mountain.
Climate and biomes
Terrestrial Biomes
• Tundra
• The Arctic Tundra encircles the earth just
south of ice-covered seas in the Northern
Hemisphere, covering 20% of the earth’s
land surface.
• The Arctic Tundra is cold and dark much of
the year; a layer of permafrost is present
in the poorly-drained soil.
The tundra
• Trees cannot grow in tundra because of
the short growing season, lack of
moisture, and permafrost.
• Tundra plants include short grasses and
sedges, along with lichens, mosses, and
short woody shrubs.
• Few animals exist in the tundra yearround, although the lemming, ptarmigan,
and musk ox are present.
• Many migrating animals, including caribou
and reindeer, and migratory birds use the
tundra during summer.
Coniferous Forests
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Coniferous forests are found in three
locations:
1) In taiga, which extends around the world
in the northern part of North America and
Eurasia;
2) Near mountain tops as montane
coniferous forests; and
3) Along the Pacific coast of North America
as temperate rain forest.
The taiga
• The taiga typifies the coniferous forest with
its cone-bearing spruce, fir, and pine trees
that are well-adapted to cold.
• Birds, bears, deer, moose, and muskrat
live around lakes and streams.
• The temperate rain forest along the west
coast of Canada and the United States
receives plentiful rainfall and is host to the
coastal redwoods.
• As an old-growth forest, it’s resources are
valuable for both conservation and
logging.
Temperate Deciduous Forests
• Temperate deciduous forests are found
south of taiga in eastern North America,
eastern Asia, and much of Europe.
• Climate is moderate with relatively high
rainfall, well-defined seasons, and a
growing season of 140 to 300 days.
• Deciduous trees, such as oak, beech, and
maple, lose their leaves in autumn.
Temperate deciduous forest
• Tallest trees form an upper canopy of leaves, yet
enough sunlight filters through to understory trees,
a shrub layer, and plant growth on the forest floor.
• Such stratification provides a variety of habitat for
birds, insects and ground life.
• Amphibians and reptiles find a home in deciduous
forest where winters are moderate.
• Autumn fruits, nuts, and berries provide food for
winter, and leaves turn brilliant colors.
• Deciduous forest soils are rich with humus and
minerals.
Tropical Forests
• In the tropical rain forests near the
equator, the weather is always warm and
rainfall is plentiful.
• This may be the most diverse biome, both
in terms of numbers of species and their
abundance.
• A tropical rain forest has a complex
structure with many layers of life, including
tall trees and their epiphytes.
Tropical rain forest location
Levels of life in a tropical rain forest
• Most animals live in the trees of the
tropical rain forest.
• Insect life is so abundant that most
species have yet to be identified.
• Termites and ants have an important role
in decomposition.
• Bird and amphibian life is very diverse.
• Primates feed on fruit in the trees.
• Soils are poor and nutrient-depleted;
nutrients are rapidly recycled among
plants.
Animals of the tropical rain forest
Shrublands
• Shrubs are shorter than trees with a woody
persistent stem and no central trunk.
• Shrubs have small but thick evergreen
leaves, with a protective waxy coating.
• Shrubs are adapted to drought and fire and
often require fire for seed germination.
• Dense shrubland in California is chaparral;
it lacks an understory and is highly
flammable.
Shrubland
Grasslands
• Grasslands occur where rainfall is greater
than 25 cm but insufficient to support
trees.
• Natural grasslands once covered 40% of
the land surface but most of this area has
been converted to agriculture.
• Grasses tolerate a high degree of grazing,
flooding, drought, and fire.
• Large herds of bison once roamed the
prairie.
The prairie
• Savannas, which are grasslands that
contain some trees, occur where a
relatively cool dry season is followed by a
hot, rainy one.
• The African savanna supports the greatest
variety and number of large herbivores of
all the biomes, including elephants,
giraffes, antelopes, zebras, wildebeests,
water buffalo, and rhinoceroses.
• Termites build towering nests and tend
their fungal gardens.
The savanna
Deserts
• Deserts are found at 30o north and south
latitudes and are characterized by low
precipitation (under 25 cm annually).
• Some deserts, such as the Sahara, have
no plants, but others, such as the North
American desert, have succulent plants,
such as cacti, adapted to water
conservation.
• Reptiles and insects, along with running
birds and rodents, are desert residents.
The desert
Aquatic Communities
• Aquatic communities can be classified as
freshwater or saltwater.
• The two sets of communities interact and
are joined by the water cycle.
• Gravity eventually returns all fresh water to
the sea, but meanwhile, it is contained as
standing water in lakes and ponds, or as
flowing water within streams and rivers.
Freshwater and saltwater
communities
• When rain falls, some of the water
percolates into the ground; the top of the
saturation zone is called the groundwater
table.
• Sometimes groundwater is also located in
underground aquifers.
• Humans have altered aquatic habitats and
drained wetlands.
• These activities degrade ecosystems and
contribute to seasonal flooding.
Lakes
• Lakes are bodies of freshwater often
classified by their nutrient status.
• Oligotrophic lakes are nutrient-poor and
have low productivity.
• Eutrophic lakes are nutrient-rich and have
high productivity.
• Through the activities of both nature and
humans, oligotrophic lakes become
eutrophic through large inputs of nutrients;
this is called eutrophication.
Types of lakes
• In the temperate zone, lakes are stratified in
the summer and winter.
• In summer, the upper layer, or epilimnion, is
warm from the sun; the middle thermocline
experiences a sharp drop in temperature;
and the lowest layer, or hypolimnion, is
cold.
• In the fall, the whole lake cools and mixes,
resulting in fall overturn; nutrients are
redistributed throughout the lake.
• Vertical stratification also exists in winter;
spring overturn follows spring warming.
Lake stratification
Life Zones
• Microscopic floating organisms in lakes are
called plankton; phytoplankton are
photosynthesizing algae, and zooplankton
are the tiny animals that eat them.
• The littoral zone of a lake is closest to the
shore, the limnetic zone is the sunlit open
area, the profundal zone is below the level
of light penetration, and the benthic zone is
at the soil-water interface.
Zones of a lake
Coastal Communities
• Near the mouth of a river, a salt marsh in
the temperate zone or a mangrove swamp
in the subtropical and tropical zones is
likely to develop.
• The silt carried by the river may form
mudflats.
• Seacoasts, mudflats, salt marshes, and
mangrove swamps all belong to one
ecological system.
Estuaries
• An estuary is a partially enclosed body of
water where fresh water and salt water
mix.
• Organisms living there must be able to
tolerate changing salinity.
• Estuaries trap nutrients delivered by rivers
and act as nurseries for larval fish.
• Estuaries are the feeding grounds for man
birds, fish, and shellfish.
Estuary structure and function
Types of estuaries
Seashores
• The littoral zone of the seashore lies
between the high and low water marks of
the tide.
• The littoral zone of a rocky beach is
divided into subzones, each of which has
characteristic attached algae and animals.
• Invertebrates living on sandy shores must
burrow underground.
Seacoasts
Oceans
• Climate is driven by the sun, but the
oceans play a major role in redistributing
heat in the biosphere.
• When the wind blows strongly and steadily
across a great expanse of ocean, the
moving air drags water along with it,
creating ocean currents.
• Major ocean currents, such as the Gulf
Stream, move heat from the equator to
cooler parts of the biosphere.
Ocean currents
• In the Southern Hemisphere, the
Humboldt Current carries phosphorus-rich
cold water northward along the west coast
of South America.
• During upwelling along this coast, cold
offshore winds cause nutrient-rich waters
to rise, enabling an abundance of marine
life to thrive there.
• Sometimes the Humboldt Current is not as
cool as usual, fisheries fail, and climate
patterns change; this is the El Niño –
Southern Oscillation.
Pelagic Division
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An ocean is divided into the pelagic and
the benthic division.
The pelagic division includes the neritic
province (overlying the continental shelf)
and the oceanic province (open ocean).
The oceanic province lacks the inorganic
nutrients of the neritic province but still
supports an abundance of plankton and
fish.
Marine environment
• The epipelagic zone of the oceanic
province is sunlit and supports
phytoplankton that in turn become food for
zooplankton, which then feed fish.
• Animals in the mesopelagic zone are
carnivores adapted to dim light;
translucent or luminescent organisms exist
there.
• The bathypelagic zone is in complete
darkness; carnivores and scavengers are
found in this zone.
• Coral reefs are areas of biological
abundance found in shallow, warm tropical
waters.
• Their chief constituents are stony corals
with a limestone exoskeleton, and
calcareous red and green algae.
• A coral reef is densely populated with a
great diversity of sponges, sea squirts,
crabs, and exotic fish.
Benthic Division
• The benthic division includes organisms
living on or in the soil of the continental
shelf (sublittoral zone), the continental
slope (bathyal zone), and the abyssal plain
(abyssal zone).
• Organisms of the benthic division depend
on the debris that floats down from above.
• Unique food chains are based on
chemosythesis at hydrothermal vents on
the ocean bottom.
Ocean inhabitants
Chapter Summary
• The spherical earth causes different
amounts of sunlight to be received at
different latitudes, resulting in differences in
temperature from the equator to the poles.
• The tilt and rotation of the earth cause the
four seasons.
• Rising and falling air currents trigger moist or
dry areas across the globe.
• Topography also influences rainfall patterns.
• Terrestrial biomes are distributed according
to climate; moisture and temperature
determine major types of vegetation.
• Terrestrial biomes include tundra, coniferous
forest (taiga), temperate deciduous forest,
tropical rain forest, shrublands, grasslands,
savanna, and deserts.
• Each biome has characteristic organisms.
• Streams, rivers, lakes, ponds, and
wetlands are different freshwater
communities.
• Lakes in temperate zones undergo
seasonal stratification and overturn.
• Lakes and ponds have life zones.
• Estuaries and coral reefs are highly
diverse saltwater communities.
• An ocean has a pelagic and a benthic
division.