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الشيماء الاعدادية - ادارة النزهة التعليمية

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    LIVING IN THE OCEAN/بحث عمل الطالبة / شروق أشرف 2/4

    شاطر

    Roully Fadel
    مشرفة اللغة الانجليزية
    مشرفة اللغة الانجليزية

    عدد المساهمات : 426
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    تاريخ التسجيل : 04/01/2010
    الموقع : مشرفة اللغة الانجليزية
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    LIVING IN THE OCEAN/بحث عمل الطالبة / شروق أشرف 2/4

    مُساهمة من طرف Roully Fadel

    LIVING IN THE OCEAN

    Whales are large, magnificent, intelligent, aquatic mammals. They breathe air through blowhole(s) into lungs (unlike fish who breathe using gills). Whales have sleek, streamlined bodies that move easily through the water. They are the only mammals, other than manatees (seacows), that live their entire lives in the water, and the only mammals that have adapted to life in the open oceans.


    Whales breathe air. They are NOT fish. They are mammals that spend their entire lives in the water.




    Cetaceans are the group of mammals that includes the whales, dolphins, and porpoises.

    Like all mammals:

    • Whales breathe air into lungs,
    • Whales have hair (although they have a lot less than land mammals, and have almost none as adults),
    • Whales are warm-blooded (they maintain a high body temperature),
    • Whales have mammary glands with which they nourish their young,
    • Whales have a four-chambered heart.


    SIZE

    The biggest whale is the blue whale, which grows to be about 94 feet (29 m) long - the height of a 9-story building. These enormous animals eat about 4 tons of tiny krill each day, obtained by filter feeding through baleen. Adult blue whales have no predators except man.

    The smallest whale is the dwarf sperm whale which as an adult is only 8.5 feet (2.6 m) long.


    The
    blue whale is the largest animal that has ever existed on Earth. It is larger than any of the dinosaurs were. They are also the loudest animal on Earth.




    TWO TYPES OF CETACEANS
    Cetaceans include the whales, dolphins and porpoises. There are over 75 species of Cetaceans. Whales belong to the order Cetacea (from the Greek word "ketos" which means whale), which is divided into the following groups:

    Toothed whales (Odontoceti) - predators that use their peg-like teeth to catch fish, squid, and marine mammals, swallowing them whole. They have one blowhole (nostril) and use echolocation to hunt. There are about 66 species of toothed whales.

    Baleen whales (Mysticeti) - predators that sieve tiny crustaceans, small fish, and other tiny organisms from the water with baleen. Baleen is a comb-like structure that filters the baleen whales' food from the water. Baleen whales are larger than the toothed whales and have 2 blowholes (nostrils). There are 10 species of baleen whales.


    SWIMMING AND OTHER WATER ACTIVITIES

    Whales have a streamlined shape and almost no hair as adults (it would cause drag while swimming). Killer whales and Shortfin Pilot whales are the fastest, swimming up to 30 miles per hour (48 kph).

    Whales swim by moving their muscular tail (flukes) up and down. Fish swim by moving their tails left and right.


    Breaching: Many whales are very acrobatic, even breaching (jumping) high out of the water and then slapping the water as they come back down. Sometimes they twirl around while breaching. Breaching may be purely for play or may be used to loosen skin parasites or have some social meaning.

    Spyhopping: This is another cetacean activity in which the whale pokes its head out of the water and turns around, perhaps to take a look around.

    Lobtailing: Some whales stick their tail out of the water into the air, swing it around, and then slap it on the water's surface; this is called lobtailing. It makes a very loud sound. The meaning or purpose of lobtailing is unknown, but may be done as a warning to the rest of the pod of danger.

    Logging: Logging is when a whale lies still at the surface of the water, resting, with its tail hanging down. While floating motionless, part of the head, the dorsal fin or parts of the back are exposed at the surface.

    MIGRATION

    Many ceteaceans, especially baleen whales, migrate over very long distances each year. They travel, sometimes in groups (pods), from cold-water feeding grounds to warm-water breeding grounds.

    Gray whales make the longest seasonal migration of any of the whales. They travel about 12,500 miles each year.


    SOCIAL BEHAVIOR
    Cetaceans have very strong social ties. The strongest social ties are between mother and calf. A social group of whales is called a pod. Baleen whales travel alone or in small pods. The toothed whales travel in large, sometimes stable pods. The toothed whales frequently hunt their prey in groups, migrate together, and share care of their young.

    REPRODUCTION

    Cetaceans give birth to live young which are nourished with milk from their mothers - they don't lay eggs. Cetaceans breed seasonally, usually in warm tropical waters, and females usually have one calf every 1-3 years. The gestation times range from 9-18 months. Whale calves can swim at or soon after birth. Mother whales care for their young for an extended period of time, usually at least a year, feeding them milk and protecting them.

    Young cetaceans are frequently mottled in color, camouflaging them from predators. Newborns have a sparse covering of hair which they lose as adults.


    WHALE SONGS
    Complex whales songs can be heard for miles under the water. The humpback's song can last for 30 minutes. Baleen whales sing low-frequency songs; toothed whales emit whistles and clicks that they use for echolocation The songs are thought to be used in attracting mates, to keep track of offspring, and for the toothed whales, to locate prey.

    CLASSIFICATION OF CETACEANS
    Cetaceans are divided into the following suborders:

    • Odontoceti (toothed whales) - killer whales or orcas , beluga whales , narwhals , sperm whales , the beaked whales, dolphins , and porpoises.
    • Mysticeti (mustached whales) or baleen whales - blue whales , humpback whales , gray whales ,bowhead whales , minke whales, and right whales. These large whales are filter feeders and are among the largest animals on earth. They have baleen plates instead of teeth, which are used to filter tiny organisms, like krill and small fish from the water. They use their tongue to dislodge the food from the baleen and swallow it. Baleen is made of keratin, the same protein that our hair and nails are made of.
    • Archaeoceti - the extinct whales, which includes Basilosaurus, the earliest known primitive Eocene whale.

    PRIMITIVE WHALES AND EVOLUTION
    Primitive whales evolved during the mid-Eocene period, about 50 million years ago. Fossil remains indicate that whales evolved from hoofed land mammals - perhaps the shore-dwelling, hyena-like Mesonychid that returned, bit by bit, to the sea roughly 50 million years ago.

    Another possible step in whale ancestry is the otter-like Ambulocetus, an extinct mammal the size of a sea lion, 10 feet (3 m) long and about 650 pounds. Its limbs allowed it to swim and could also support it on land. It had long, powerful jaws with shark-like teeth, a small brains, and a pelvis fused to its backbone (like land-dwelling mammals but unlike whales).

    Basilosaurus, a very primitive, extinct whale, had a tiny head and pointed snout with teeth, unlike modern-day whales which have large heads and a blunter snout. It was about 82 feet (25 m) long.
    There are many species of whales that are in danger of going extinct. Most baleen whales (the huge whales targeted by commercial whalers) are listed as endangered or protected species. Most other whale species are doing well and are not endangered.



    _________________
    Roully Fadel
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      الوقت/التاريخ الآن هو الخميس ديسمبر 08, 2016 2:50 am