Under the sea 教學(xué)設(shè)計(jì)
step 8 debate
the last whaling station in australia closed in 1978.whales are now an endangered species and protected by an international ban，but some countries oppose the ban.in groups discuss the reasons for and against banning whaling.
step 9 homework
1.write down the useful new words and expressions，then learn them by heart.
2.write down an anecdote in the name of old tom，the baleen whale or james.
備課資料
physical description
the killer whale，or orca，is the largest member of the dolphin family.killer whales are large and robust with a blunt head and reduced beak.with their striking pigmentation，they are not often confused with other species in their natural setting.orcas are jet black with a white patch behind and above the eyes.the lower jaw and throat are also white，contiguous with a white belly patch that extends back to the genital region.the undersides of the flukes are white and white lobes extend upwards from the white belly to behind the dorsal fin.a grey saddle patch is found behind the dorsal fin，the shape of which is unique to individual whales.the tall dorsal fin of mature animals，especially males，can reach up to 1.8 meters(5.9 feet).males reach 8.5 meters(28 feet)in length，while females reach 6.7 meters(22 feet).
natural history
killer whales are one of the most cosmopolitan species of whales，with a distribution that spans tropical oceans and arctic seas.they are highly social and form strong and persistent social bonds with their pod members.pods are made up of extended family members and 2 or more pods may come together for short periods to mate.the world's killer whale population seems to consist of subpopulations adapted to live within the specialized niche of their environment.a pod's movements tends to follow those of their intended prey which，depending on location，may include salmon herring，baleen whales，penguins and seals.
status
in canada，killer whales are listed as threatened by the committee on the status of endangered wildlife(cosewic)and are protected under the new federal species at risk act(sara).other populations worldwide may be protected under specific national legislation.
threats to the species
although the global population of killer whales is not endangered，different regional populations are depleted.resident and transient populations off the coast of vancouver，canada and washington state，u.s.，were depleted by the live capture fishery for aquaria that occurred before scientists knew how many killer whales existed in the population.today these populations number only a few hundred whales and are threatened by pollution，heavy ship traffic，and possibly reduced prey.because of the killer whales' popularity，there are concerns that intensive whale watching operations may drive whales from their preferred habitat.as well，noise－making devices attached to salmon cages to scare off predators may also force whales out of their preferred habitat，affecting their ability to feed.some orca populations are also hunted in japan，indonesia，greenland and the west indies.