Evolution of Elephants sample essay
Elephant is the largest land mammal and the second largest of all animals, exceeded only by some whales. Elephants occur in tropical regions of India, Ceylon, and adjacent areas of Asia and in Africa. They are popular attractions in zoos, parks, and circuses throughout the world. The elephant is a tall, very strong animal with a large head; large ears; a very long trunk or proboscis; ivory tusks; a thick neck; thick, straight, columnar legs; short, broad, padlike feet; a medium-sized tufted tail; and thick, almost hairless, skin.
Although all are commonly called elephants, these animals constitute two separate genera and three species: the Indian elephant (Elaphas indicus), and the two so-called African elephants (Lexodonta); one (L. Africana) inhabiting bushlands and the other (L. cyclotis) living in for rested areas (YaldenLargen & Koc 1986). Mammalogists think that the two African species should be termed loxodonts, not elephants. However, the term elephant is almost universally used for all three species.
Thesis Statement: This research paper intent to: (1) know how these species evolved from their ancestors till present and became extinct; (2) be aware the changes in `all` structures and genes of the elephants took place from the start until now; (3) discuss their changes in morphological characteristics till today and its biogeography. II. Background A. Classification and Evolution The three species of elephants are classified in the family Elephantidae of the order Proboscidea.
Their only living relatives are two apparently unrelated types of animals—the hydraxes (Conies of the Bible) and the sirenians, of which there are two types, the manatees, and the dugongs. These three groups appear to have had a common ancestry The earliest known type of elephant was a tapirlike, pig-sized animal, Moeritherium, the remains of which have been found in Upper Eocene deposits (some 60 million years old) in Egypt. The “original ancestor” must have lived considerably earlier, since Moeritherium already showed the beginnings of the specialized dentition of what we now call elephants (King, Hamilton & Vollrath 2007).
Many varied and in some cases rather bizarre types of so-called “proboscideans” are known from fossil remains, but most of these seem not to be on the main stem of elephant evolution. The main evolutionary stem of the living stem of the living elephants comprised two families—the mastodons (Mastodontidae) and the elephants (Elephantidae). The mastodons, now extinct, were elephantlike in appearance but constituted a quite separate group, as evidenced in particular by the structure and development of their teeth.
The Elephantidae family includes both the present-day elephants (Elephas and Loxodonta) and the now extinct mammoths (Mammuthus) (see Saving the African Elephant). Some mastodons and mammoths survived in North America until about 8,000 years ago, and were contemporary with early man. The true elephants are comparatively recent. No fossils are known from deposits earlier than the late Pliocene, some 12 to 12 million years ago. Though elephants apparently originated in Africa and are now found only in Africa and Southeast Asia, they once roamed most of the earth (Parker, & Amin 1983).
III. Discussion A. Structures, Descriptions and Morphology The African bush elephant is the largest land mammal in the world. The record height—that of a specimen now in the Smithsonian Institution in Washington, D. C. —is 13 feet, 2 inches (4 meters) at the shoulders. A large bull, or male, bush African elephant may weigh 6 tons (5. 4 metric tons) or more. Females’ type of African elephants is also smaller, rarely exceeding a height of 8 feet (2. 4 meters) (Parker, & Amin 1983). An African elephant is usually swaybacked with the high point either at the shoulders or at the rump.
It carries its head at an angle of 450 upward and has a protracted head with a sloping forehead and a single dome above the trunk. It has very large, fan-shaped ears, sometimes measuring 5 feet (1. 5 meters) from top to bottom and 3 ? feet (1 meter) in width (Sukumar 2003). The ears are lobed in the forest species, lobeless in the bush species. The record height for an Indian elephant is variously given from 10 feet, 7 ? inches to 11 feet (3. 2-3. 3 meters) and that for a specimen from Ceylon at about 12 feet (3. 6 meters). The Indian elephant differs somewhat in overall shape from the African elephants.
It has a straight or arched back with the high point about central. It carries its head at right angles to the long axis of its body and has a short face with a bulging forehead that forms two domes on the front of the temples (Williams 2002). Its rather small triangular cars are pointed at the bottom front. Trunk. The elephant’s trunk is formed from its nose and upper lip. It is long, tubular, muscular, flexible, and sensitive. Nostrils are located at its tip. In the Indian elephant the trunk is covered with small wrinkles but is nonetheless comparatively smooth.
It has a single fingerlike projection on its upper tip. In the African elephants, the trunk is cross-corrugated and has two fingerlike projections above and below at its tip (Todd 2005). The trunk is a keen organ of smell, helping the elephant to locate food and enemies. Elephants also use the trunk to examine or pick up objects and to give themselves dust or water baths. Tusks and Teeth. Elephant tusks are greatly elongated, specialized, and generally curved upper incisor teeth. The tusks grow continuously throughout the elephant’s life, the elephants using them to dig for food and as weapons.
In African elephants, both males and females have tusks, but those of females are usually smaller. Male forest elephants often have slender tusks over 10 feet (3 meters) long. The official record for a bush type African elephant’s tusks is 11 feet, 5 1/3 inches (3. 45 meters) for the left tusk and 11 feet (3. 3 meters) for the right tusk, with a combined weight of 293 pounds (133 kg). Tusks frequently vary in length, depending on whether the animal is left or right handed, but the difference is rarely more than 6 inches (15 cm) (Williams 2002).
Male Indian elephants have smaller tusks, about 5 or 6 feet (1. 5-1. 8 meters) long. The females are tuskless or have tushes-long pointed teeth—that remain in the gums, pointing downward, and usually breaks or drops off. In addition to these specialized incisors, elephants have oval-shaped molars with flat crowns. Each tooth is composed 1 foot (30 cm) by 4 inches (10 cm), covered with enamel and crossed by a series of alternating cross ridges. There are only four teeth present at any one time—two in the lower jaw and two in the upper jaw.
As the teeth wear down, they are continuously replaced, coming in successively from the back (Williams 2002). Skin, Nails, and Glands. In all elephants the skin is thick, rather dry, and only sparsely covered with hair. Indian elephants and African forest elephants have dark, fairly smooth skin and five nails on the front feet, four on the rear feet. The African bush elephant differs, having pale gray, very rough skin, and four nails on the front feet, three on the rear. There are no sebaceous glands to lubricate the skin, but there are four sets of salivary glands. The mammary glands are just behind the front legs.
The tests are internal, and the penis can be withdrawn into the body, sometimes making it difficult to distinguish a make from a tusked female (YaldenLargen & Koc 1986). • Behavior Elephants are gregarious animals, often associating in herds of 25 to 30 individuals or more. Elephants living alone sometimes become dangerous and are then called rogues. In general, elephants display a wide complex of social rules and regulations, extraordinary discipline, and recognizable customs. Locomotion. Despite their bulk, elephants can move virtually without a sound and very rapidly when necessary.
They normally walk at a rate of about 4 miles per hour but can charge at 25 miles an hour for a short distance. They walk on the tips of their toes with the rest of the foot a large wedge-shaped pad supporting the enormous weight of the animal (Parker, & Amin 1983). Indian elephants also appear to be very strong swimmers, able to regulate their buoyancy by swallowing air. The African forest elephant is also probably a good swimmer—in any case, it spends a lot of time in large rivers. Both of these elephant species have been seen walking on the bottom of shallow waters, holding their trunks aloft as snorkels (Parker, & Amin 1983).
The African bush elephant is not known to take deep water deliberately and there is considerable doubt as to whether it knows how to swim. Nomadic Habits. Elephants do not seem to have a permanent home, but wander some distances, largely to find sufficient food. There is considerable historical evidence that some of the elephants of Asia once performed annual migrations of quite wide extent, notably in those areas of India where vegetative growth is seasonal. The African bush elephant apparently also used to move around enormous circular routes, taking up to ten years to complete the trip (Sukumar 2003). Feeding.
Elephants are herbivores. They eat all types of grasses and sedges, some leaves, much fallen fruit, and greet nuts. The best estimate of the amount of fodder needed per 18 hours to keep an elephant healthy is 800 to 1,000 pounds for African bush elephants, 600 to 700 pounds for Indian elephants. In a few rare cases, Indian elephants have become carnivorous (Sukumar 2003), but seem that this is a pathological condition for them. Elephants drink a large amount of water, from 20 to 40 gallons a day. Perception. Elephants have small eyes and poor vision, and despite their relatively large ears have only limited hearing.
Their sense of smell is, however, astonishingly acute. They seem to be able to detect unerringly even supposedly odorless poisons. Their senses of touch and balance are also extraordinary. Intelligence and Emotions. Elephants seem to be extremely intelligent and individualistic. They can make a great variety of sounds and definitely use sounds to communicate among themselves. They also appear to have complex emotions and very pronounced personalities. In fact, they act like human beings, seeming to reason and act logically.
They have been known to cry from sheer frustration (Williams 2002); to commit “mercy killing” on an incurably ill member of their herd; to help—by lifting or supporting—a wounded or ill member of the herd; to rescue captured members of the herd; and to rescue humans from other elephants or from natural or man-made disasters. Elephants suffer much from neuroses, and some seem to be born insane or to become insane (Williams 2002). Musth. Almost all male and some female elephants suffer from a peculiar and little understood condition called musth. Musth occurs usually once a year, comes on suddenly, and may last from a week to five months.
During this time, a tarlike substance is exuded from a gland between the eyes and the mouth. The animal may go berserk or may become dazed and sick (King, Hamilton & Vollrath 2007). Although many mammalogists have long thought that musth was a sexual manifestation, there is no concrete evidence to substantiate this theory. There is no definite breeding season for elephants. The gestation period is 18 to 22 months in the Indian elephants. One, very rarely two, young are born. Other females, called aunties by the Burmese, assist a mother both before and during the birth of the young.
African elephants seem to wait a certain period of time between a birth and the next copulation (King, Hamilton & Vollrath 2007). IV. Conclusion As a conclusion, elephants have been trained in sic distinct fields—warfare, hinting, transport, work, parading, and entertaining or performing. Each of these fields requires special training, and an animal trained in one field can rarely be successfully retrained in another. One of the first known uses of elephants was in warfare, with the best known example that of Hannibal who marched elephants over the Alps to attack Rome in the late 3d century B.
C. Elephants were not particularly reliable for warfare, however, since they ran wild as soon as their trainer, the mahout, or oosie, was killed. Moreover, African elephants are more difficult to train than Indian elephants. Indian elephants are easily tamed and are used as draft animal throughout southern Asia.
Lucy E. King, Iain Douglas-Hamilton, Fritz Vollrath (2007) African elephants run from the sound of disturbed bees. Current Biology 17: R832-R833 Parker, Ian; Amin, Mohammed (1983). Ivory Crisis, Chatto and Windus, London. pp. 184. Saving the African Elephant.
The Futurist, Vol. 23, September 1989 Sukumar, R. (2003). The Living Elephants: Evolutionary Ecology, Behavior, and Conservation. Oxford University Press. New York. Todd, N. E. (2005). Reanalysis of African Elephas recki: implications for time, space and taxonomy. Quaternary International 126-128:65-72. Williams, S. (2002). Africa’s Elephant. African Business Yalden, D. W. , M. J. Largen and D. Kock (1986), Catalogue of the Mammals of Ethiopia. 6. Perissodactyla, Proboscidea, Hyracoidea, Lagomorpha, Tubulidentata, Sirenia, and Cetacea, Italian J. Zool. , Suppl. , n. s. , 21:31-103.
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