3-7~5-1

3-7
How do scientists study ecosystems?

Scientists use field research , laboratory research , and mathematical and other models to learn about ecosystems.

4-1
What is biological evolution and how dose it occur?

The scientific theory of evolution explain how life on earth changes over time through changes in the genes of populations.
Populations evolve when genes mutate and give some individuals genetic traits that enhance their abilities to survive and to produce offspring with these traits (natural selection).

4-2
How do geological and climate changes affect evolution ?

Tectonic plate movements , volcanic eruptions,earthquakes,and climate change have shifted wildlife habitats,wiped out large numbers of species , and created opportunities for the evolution of new species.

4-3
What is an ecological niche?

As a result of bioligical evolution,each species plays a specific ecological role called its niche.

4-4
How do extinction , speciation , and human activities affect biodiversity?

As environmental conditions change , the balance between formation of new species and extinction of existing ones determines the earth's biodiversity.

Human activities can decrease the earth's biodiversity by causing the premature extinction of species and by destroying or degrading habitats needed for the development of new species.

4-5
How might genetic engineering affect evolution?

Genetic engineering enables scientists to thansfer genetic traits between different species_a process that holds great promise and raise difficult issues.

5-1
What factor influence climate?

An area's climate is determined mostly by solar radition,the earth's rotation,global patterns of air and water movements , gases in the atmosphere, and the earth's surface featrues.