Download Chapter 14 - Ecosystems

Chapter 14 - Ecosystems
14.1 What is an Ecosystem
14.2 Cycles Within Ecosystems
14.3 Kinds of Ecosystems
14.1 What is an Ecosystem?
• Ecology – means “study of the house” or the
place where one lives. It is the study of the
interactions of organisms with one another
and with their physical environment.
• Community – the organisms that live in a
particular place, such as a forest.
• Habitat – the physical location of a
community. Example: the habitat is the
neighborhood and the community is the
residents of the neighborhood.
• Ecosystem – the sum of the community and
the habitat. It is a self-sustaining collection of
organisms and their physical environment.
• Diversity – the measure of the number of
species living there. The tropical rain forests
are the most diverse terrestrial ecosystem
having as many as 100 species of trees in the
size of two football fields.
• Ecology is studied to help prevent pollution,
conserve resources and preserve the world for
your children.
• Ecosystems are very complex and normally
function with interference by humans. Now
some ecosystems require our help because we
have caused them great damage.
• It is difficult to determine how an ecosystem
works because it can contain thousands of
interacting species.
• Two basic questions:
– Where does the energy come from that is needed by
particular animals and plants?
– How do organisms in the ecosystem acquire adequate
amounts of minerals and other inorganic substances
they need?
• Answering these two questions will give a
good idea of how an ecosystem normally
works. Then you can ask how an ecosystem
might be expected to respond to a
disturbance. Scientists make ecological
models to predict how different changes
would affect the whole system.
• Every ecosystem requires energy. How many
and what kinds of organisms live in an
ecosystem is determined by the amount of
energy available to the system.
• Producers – organisms in energy from their
surroundings and store it in complex molecules.
Nearly all producers are photosynthetic.
Producers are plants, some bacteria and algae.
• Consumers – all other organisms. They capture
their energy by consuming other organisms.
Animals, most protists and bacteria, and fungi are
all consumers.
• Each ecosystem contains consumers called
decomposers. Decomposers obtain energy by
consuming organic wastes and dead bodies.
These include fungi (mushrooms) and some
species of bacteria.
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• Energy flows from producers to consumers.
• Every organism is assigned to a trophic level.
All members of a trophic level are the same
number of energy-transferring steps away
from the sun.
• Producers (plants) are the first trophic level.
Plants and other organisms that make their
own food are called autotrophs.
• Plant eaters (herbivores) are in the second
trophic level. This includes cows, caterpillars,
elephants and ducks.
• Animals that feed on the plant eaters are in the
third trophic level. All organisms in the third
trophic level or above are carnivores (flesh
eaters). Carnivores at the third level feed on
herbivores, and carnivores above the third
trophic level feed on other carnivores. Tigers,
hawks, weasels, pelicans and killer whales are all
carnivores.
• Omnivores (bears and humans) eat both plants
and animals.
• Because they cannot make their own food,
organisms in trophic levels above the first trophic
level are heterotrophs.