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By HngLy
#989783 Link tải luận văn miễn phí
Unit 1
Types of species in ecosystems
A. Reading
* Warm-up Activities
- How important are species in ecosystems?
- How many kinds of species do you know?
One way to look at an ecosystem's species from a human standpoint is to divide them into
four types:
- Native species, which normally live and thrive in a particular ecosystem.
- Immigrant, or alien species, which migrate into an ecosystem or which are
deliberately or accidentally introduced into an ecosystem by humans. Some of these
species are beneficial to humans, while others can take over and eliminate many
native species.
- Indicator species, which serve as early warnings that a community or an ecosystem is
being damaged. For example, the present decline of migratory, insect-eating
songbirds in North America indicates that their summer habitats there and their winter
habitats in the tropical forests of Latin America and the Caribbean are rapidly
- Keystone species affect many other organisms in an ecosystem. For example, in
tropical forests, various species of bees, bats, and humming - birds play keystone
roles in pollinating flowering plants, dispersing seed, or both. Some keystone species,
such as the alligator, the wolf, the leopard, the lion, the giant anteater, and the giant
armadillo, are top predators that exert a stabilizing effect on their ecosystems by
feeding on and regulating the populations of certain species. The loss of a keystone
species can lead to population crashes and extinctions of other species that depend on
it for certain services - a ripple or domino effect that spreads throughout an
ecosystem. According to biologist E.O.Wilson, "The loss of a keystone species is like
a drill accidentally striking a power line. It causes lights to go out all over".
(Taken from "Sustaining the Earth" by Tyler Miller, G)
I. Omprehension questions
Answer the following questions
1. How are species in an ecosystem classified?

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