The Food Web

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The Food Web
Energy is transformed in ecosystems as it is
transferred from plants to animals and yet more
animals in a food chain or food web. Energy is
lost with each step. In each ecosystem, such as
in a salt marsh, there are consequently fewer
individuals of species higher up the food chain
than lower down.
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The Food Web
Energy loss Percentage of energy passed up the
steps of the food chain, assuming 90 percent is
lost energy at each step.
Flow diagram of a salt-marsh ecosystem in winter.
The arrows show how energy flows from the sun to
producers, consumers, and decomposers.
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Food Pyramids
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Photosynthesis and Respiration
Photosynthesis is the production of carbohydrate,
a general term for a class of organic compounds
consisting of carbon, hydrogen, and
oxygen. Respiration is the opposite to
photosynthesis, in that carbohydrate is broken
down and combined with oxygen to yield carbon
dioxide and water. Photosynthesis and respiration
link in a continuous cycle involving primary
producers, consumers, decomposers.
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Photosynthesis and Respiration
A simplified flow diagram of the essential
components of photosynthesis and respiration
through the biosphere.
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Natural Vegetation Regions of the World
Biogeographers recognize principal biome types
forest, savanna, grassland, tundra and desert.
The biomes are further broken down into smaller
vegetation units called formation classes. The
following is a list of natural vegetation regions
found around the globe Equatorial and
tropical-zone rainforests Monsoon forest,
savanna woodland, thorntree-tall grass savanna
Subtropical evergreen forest Midlatitude
deciduous forest Cold needleleaf forest and
coastal forest Sclerophyll vegetation
Tall-grass prairie Short-grass prairie
Semidesert Desert shrub and desert Arctic and
alpine tundra Ice, ice sheet. See animation on
natural vegetation regions in the geodiscoveries
section of your texts website.
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Biomes
Tundra
Grassland
The grasslands or prairies have an average
rainfall between 25 and 75 centimeters (10-30
inches). The summers are hot and the winters
cold. The grasses, unlike the trees, can
tolerate the long periods without rain. The
grasses have large root systems that seek out the
moisture to depths of as much as two meters below
the surface of the ground.
Tundras are extremely cold areas with land that
remains frozen year-round. The vegetation
consists mainly of short shrubs and grasses.
Animals of this area are musk oxen, lemmings,
reindeer and caribou.
Taiga
Alpine Forest
Taigas are forests of dense evergreen trees. The
climate in these areas is generally cold with
plenty of snowfall. Animals found here include
beavers, brown bears and wolverines.
Alpine forests are found in high mountains.
Alpine vegetation is found scattered in the
mountainous regions of the world. Plants here
have to contend with harsh conditions cold
temperatures, high winds, and heavy snowfall.
Therefore, alpine vegetation grows low to the
ground in alpine meadows.
Temperate Forest
Temperate forests have high levels of rainfall
and humidity. Trees, plants and shrubs grow in
the spring and summer seasons, then become
dormant in winter. Wolves, birds, squirrels and
foxes are examples of animals that live here.
Desert
Deserts are typically dry areas that experience
extremely small amounts of rainfall. They can be
either cold or hot. Vegetation includes shrubs
and cactus plants. Animals include birds and
rodents. Snakes, lizards and turtles survive the
severe temperatures by hunting at night and
making their homes underground.
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Biomes (Continued)
Rainforest
Rainforests are characterized by dense
vegetation, seasonally warm temperatures, and
abundant rainfall. The animals that dwell here
depend on trees for housing and food. Some
examples are monkeys, bats, frogs and insects.
Chaparral
Chaparrals, found in coastline regions, are
characterized by dense shrubs and grasses. The
climate is hot and dry in the summer and rainy in
the winter, with low precipitation (overall).
Chaparrals are home to deer, snakes, birds and
lizards.
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Nutrient Cycles
The Carbon Cycle
The Water Cycle
The Nitrogen Cycle
The Phosphorus Cycle
See animation on nutrient cycles in the
geodiscoveries section of your texts website.
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Biogeochemical Cycles
Most carbon is stored in the form of carbonate
sediments as well as in fossil fuel resources.
Consequently, although all life is composed of
carbon compounds of one form or another,
relatively little carbon is directly available to
organisms. The vast majority of atmospheric
oxygen is derived from photosynthesis with a very
small amount contributed by volcanic activity.
Oxygen becomes combined with carbon as carbon
dioxide in respiration and is also removed by the
process of combustion. Although the atmosphere,
composed of 78 nitrogen, is a large reservoir,
nitrogen is also added and removed by a number of
processes. Denitrifying bacteria send nitrogen in
the soil to the atmosphere, while nitrifying
bacteria act to fix nitrogen in the soil from the
atmosphere.
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Biogeochemical Cycles
a).
b).
c).
a). The Carbon Cycle b). The Oxygen Cycle c).
The Nitrogen Cycle
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The Sedimentary Cycle
The sedimentary cycle moves eroded debris from
the land to the ocean via running water. It
returns, after millions of years, as uplifted
terrestrial rock. Plant macronutrients are also
recycled in the sedimentary cycle through the
biosphere and the soil.
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The Sedimentary Cycle
A flow diagram of the sedimentary cycle of
materials in and out of the biosphere and within
the inorganic realm of the lithosphere,
hydrosphere, and atmosphere.
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