英語閱讀海豚dolphins教學(xué)課件

1、DolphinsDolphin Dolphins are marine mammals closely related to whales and porpoises. There are almost forty species of dolphin in 17 genera. They are found worldwide, mostly in the shallower seas of the continental shelves, and are carnivores, eating mostly fish and squid. Rissos Dolphinbottlenose d

2、olphinOrcaKiller WhaleCommersons dolphin Dusky dolphin Indo-Pacific hump-backed dolphin Sousa chinensis BehaviorIntelligence Dolphins are often regarded as one of Earths most intelligent animals, though it is hard to say just how intelligent. Comparing species relative intelligence is complicated by

3、 differences in sensory apparatus, response modes, and nature of cognition. Social behaviorDolphins are social living in pods of up to a dozen individuals. In places with a high abundance of food, forming a super grouping may exceed 1,000 dolphins. Dolphins can establish strong social bonds; they wi

4、ll stay with injured or ill individuals, even helping them to breathe by bringing them to the surface if needed. Sleeping Generally, dolphins sleep with only one brain hemisphere in slow-wave sleep at a time, thus maintaining enough consciousness to breathe and to watch for possible predators and ot

5、her threats. Vocalizations Roughly three categories of sounds can be identified: frequency modulated whistles burst-pulsed sounds clicks. Dolphins communicate with whistle-like sounds produced by vibrating connective tissue, similar to the way human vocal cords function and through burst-pulsed soun

6、ds.Jumping Dolphins occasionally leap above the water surface, and sometimes perform acrobatic figures. Scientists are not certain about the purpose of the acrobatics. Possibilities include locating schools of fish by looking at above-water signs like feeding birds, communicating with other dolphins

7、, dislodging parasites or simple amusement.Playing Play is an important part of dolphin culture. Dolphins play with seaweed and play-fight with other dolphins. At times they harass other local creatures, like seabirds and turtles. Relationships with humansMythology Dolphins have long played a role i

8、n human culture. Dolphins are common in Greek mythology and there are many coins from ancient Greece which feature a man or boy or deity riding on the back of a dolphin. Friends of humans Dolphins are friends of human beings, they are happy to be with people. Assist fishermen fishing; Have many repo

9、rts about dolphins to save people; One report in 1959,even said that dolphins drove sharks away, then saved the victims of the passengers. Therapy Therapy for psychological problems and developmental disabilities. For example, a 2005 study found dolphins an effective treatment for mild to moderate d

10、epression. Militaryfinding minesrescuing lost or trapped humansCuisine Dolphin meat is consumed in a small number of countries world-wide, which include Japan and Peru.ThreatsHuman threats Some dolphin species face an uncertain future, especially some river dolphin species such as the Amazon river d

11、olphin, which are critically or seriously endangered. Natural threats Except for humans, dolphins have few natural enemies. A few of the larger sharks, such as great white sharkA wide variety of diseases and parasitesPollutionPesticides Heavy metalsPlasticsIndustrial and agricultural pollutants nois

12、e Loud underwater noises, such as live firing exercises, or certain offshore construction projects, such as wind farms, may be harmful to dolphins, increasing stress, damaging hearing, and causing decompression sickness by forcing them to surface too quickly to escape the noise.Hunting Various fishing methods, the use of drift and gill nets,