Chapter 35: The Biosphere

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Chapter 35 The Biosphere
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Climate and the Biosphere

• 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 earths axis as it rotates about
  the sun
• Distribution of land masses and oceans and
• Topography (landscape) features.

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Air Circulation

• The earth is a sphere, and thus the suns 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.

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Distribution of solar energy
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Seasons
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• 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.

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Global wind circulation
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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.

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Formation of a rain shadow
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• 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.

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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.

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Pattern of biome distribution
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• 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.

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Climate and biomes
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Terrestrial Biomes

• Tundra
• The Arctic Tundra encircles the earth just south
  of ice-covered seas in the Northern Hemisphere,
  covering 20 of the earths land surface.
• The Arctic Tundra is cold and dark much of the
  year a layer of permafrost is present in the
  poorly-drained soil.

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The tundra
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• 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 year-round,
  although the lemming, ptarmigan, and musk ox are
  present.
• Many migrating animals, including caribou and
  reindeer, and migratory birds use the tundra
  during summer.

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Coniferous Forests

• Coniferous forests are found in three locations
• In taiga, which extends around the world in the
  northern part of North America and Eurasia
• Near mountain tops as montane coniferous forests
  and
• Along the Pacific coast of North America as
  temperate rain forest.

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The taiga
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• 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, its resources are
  valuable for both conservation and logging.

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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.

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Temperate deciduous forest
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• 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.

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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.

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Tropical rain forest location
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Levels of life in a tropical rain forest
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• 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.

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Animals of the tropical rain forest
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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.

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Shrubland
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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.

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The prairie
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• 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.

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The savanna
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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.

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The desert
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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.

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Freshwater and saltwater communities
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• 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.

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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.

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Types of lakes
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• 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.

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Lake stratification
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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.

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Zones of a lake
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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.

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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.

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Estuary structure and function
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Types of estuaries
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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.

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Seacoasts
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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.

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Ocean currents
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• 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.

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Pelagic Division

• 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.

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Marine environment
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• 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.

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• 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.

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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.

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Ocean inhabitants
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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.

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• 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.

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• 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.