CHAPTER OUTLINE
36.1 Climate and the Biosphere
Climate refers to the prevailing weather conditions in a particular region and is dictated by
temperature and rainfall.
Effect of Solar Radiation
Because the Earth is spherically shaped, the sun’s rays are more direct at the equator and
more spread out progressing toward the poles. In addition, the Earth is on a slight tilt
away from the sun. Because the Earth rotates on its axis daily and its surface consists of
continents and oceans, warm and cold air form circulation patterns.
Other Effects
Other effects such as rain shadow, monsoons, and lake effect cause regional climate
conditions.
36.2 Terrestrial Ecosystems
A major type of terrestrial ecosystem is called a biome. Biomes are characterized by particular
climatic conditions, as well as the plants and animals living there.
Tundra
The tundra encircles the arctic region just south of the ice-covered polar seas. It is cold
and dark much of the year. In summer only the topmost layer of earth thaws; the
permafrost beneath this layer is always frozen. Trees are not found in the tundra. Only
grasses, sedges, lichens, mosses,and wood shrubs live there. Few animals live in the
tundra year-round.
Coniferous Forests
Coniferous forests are found in the taiga, near mountaintops, and along the Pacific coast
of North America. It is characterized by cone-bearing trees. Birds, bears, deer, moose,
beaver, and muskrat can be found here.
Temperate Deciduous Forests
Temperate deciduous forests are found south of the taiga in eastern North American,
eastern Asia, and much of Europe. Climate is moderate with relatively heavy rainfall and
well defined seasons. The trees lose their leaves in fall and regrow them in spring.
Herbaceous plants are found here. Squirrels, rabbits, turkeys, deer, and bears are found
in the temperate deciduous forests. Amphibians and reptiles also occur in this biome.
Abundant fruits, nuts, and berries provide a supply of food for the winter.
Tropical Forests
The most common type of tropical forest is the tropical rain forest, which is found in
areas of South America, Africa, and the Indo-Malayan region near the equator. The
temperature is always warm and rainfall is plentiful. This is the richest biome in terms of
species diversity. A tropical rain forest has a complex structure, with many levels of life.
Tropical deciduous forests have wet and dry seasons and are found in India, Southeast
Asia, West Africa, South and Central America, the West Indies, and northern Australia.
Shrublands
Shrublands occur along coasts that have dry summers and receive most of their rainfall
during their winter. They contain shrubs that are able to withstand arid conditions and can
quickly regrow after a fire.
Grasslands
Grasslands occur where rainfall is present but insufficient to support trees. Small
mammals typically live below ground but usually feed above ground and larger predators
feed on them.
Savannas
Savannas are grasslands that contain some trees and occur in regions where a
relatively cool dry season is followed by a hot, rainy one. It supports large
herbivores.
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Deserts
Deserts are usually found at latitudes of 30o, in both the Northern and
Southern Hemispheres. Days are hot and nights are cold. Plants and animals that
live here are adapted to the lack of water.
36.3 Aquatic Ecosystems
Aquatic ecosystems are classified as freshwater and saltwater. Coastal ecosystems represent areas
of brackish water.
Lakes
Lakes are bodies of fresh water often classified by their nutrient abundance. Oligotrophic
(nutrient-poor) lakes are characterized by a small amount of organic matter and low
productivity. Eutrophic (nutrient-rich) lake typically have plentiful organic matter and
high productivity. In temperate environments lakes are often stratified in summer and
winter.
Life Zones
Microscopic plankton play important roles in aquatic systems. Lakes and ponds
can be divided into several life zones: littoral, limnetic, profundal, and benthic.
Different organisms live in each zone.
Coastal Ecosystems
Estuaries
An estuary is where fresh water and salt water meet and mix. Coastal bays, tidal
marshes, fjords, some delta, and lagoons are all examples. An estuary acts as a
nutrient trap and are sometimes called the nurseries of the sea.
Seashores
Seashores are constantly bombarded by the sea as the tides roll in and out. The
littoral zone lies between the high- and low-tide marks.
Oceans
Oceans play a major role in redistributing heat in the biosphere.
Pelagic Division
The organisms of the oceans are placed into either the pelagic (open waters) or
the benthic division (ocean floor). The pelagic division includes the neritic
province and the oceanic province.
Neritic Province
The abundance sunlight and inorganic nutrients provide for a large
concentration of organisms in the neritic province. Coral reefs are areas
of high biological abundance and productivity found in shallow, nutrientpoor, tropical waters.
Oceanic Province
The oceanic province lacks the inorganic nutrients of the neritic province
and does not have as high a concentration of phytoplankton. Larger fish,
mammals and sharks are found here. Animals in the mesopelagic zone
are carnivores that are adapted to the absence of light. The bathypelagic
zone is in complete darkness.
Benthic Division
The benthic division includes organisms that live on or in the soil of the
continental shelf, the continental slope, and the abyssal plain. Hydrothermal
vents are found in the abyssal plain.
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