Cuentos Latinoamericanos

ESC.SECUNDARIA
GRAL. ALFONSO MEDINA
CASTAÑEDA

32DES0039-U

INGLÉS

PROFR. JOSÉ DIEGO LÓPEZ AGUILAR

ANTOLOGÍA

‘’DOLPHIN’’

ALUMONO: LIZBETH ALEJANDRA ARROYO GONZALEZ

2do GRADOGRUPO ‘’C’’

RIO GRANDE, ZAC., SEPTIEMBRE 2012
Dolphins
Dolphins are marine mammals closely related to whales and porpoises. There are almost forty species of dolphin in 17 genera. They vary in sizefrom 1.2 m (4 ft) and 40 kg (90 lb) (Maui's dolphin), up to 9.5 m (30 ft) and 10 tonnes (9.8 long tons; 11 short tons) (the orca or killer whale). They are found worldwide, mostly in the shallowerseas of the continental shelves, and are carnivores, eating mostly fish and squid. The family Delphinidae is the largest in the Cetacean order, and evolved relatively recently, about ten million yearsago, during the Miocene. Dolphins are among the most intelligent animals, and their often friendly appearance, an artifact of the "smile" of their mouthline, and seemingly playful attitude have madethem very popular in human culture.
Evolution
Dolphins, along with whales and porpoises, are descendants of terrestrial mammals, most likely of the Artiodactyl order. The ancestors of the modern-daydolphins entered the water roughly 50 million years ago, in the Eocene epoch.
Hind limb buds are apparent on an embryo of a spotted dolphin in the fifth week of development as small bumps (hind limbbuds) near the base of the tail. The pin is approximately 2.5 cm (1.0 in) long.
Modern dolphin skeletons have two small, rod-shaped pelvic bones thought to be vestigial hind limbs. In October 2006, anunusual bottlenose dolphin was captured in Japan; it had small fins on each side of its genital slit, which scientists believe to be a more pronounced development of these vestigial hind limbs.Anatomy
Dolphins have a streamlined fusiform body, adapted for fast swimming. The tail fin, called the fluke, is used for propulsion, while the pectoral fins together with the entire tail section...