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Evolution of Elephants

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Isabella Fabrizio

on 12 April 2013

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Transcript of Evolution of Elephants

Evolution of the Elephants have extremely
large tusks Elephants have the largest The elephant is the largest land mammal to walk the earth Elephant Isabella Fabrizio, Sara Toniolo, Sabrina Cappelli, and Nathan Vellozzo By: General
Characteristics ears of any animal Elephants have excellent hearing. However, their ears also act as giant cooling systems As they heat up, they are able to open more
in their ears. All 100 gallons of blood can be run through their ears in 20 minutes. Elephants cannot sweat. blood vessels its ears also allows an elephant to keep itself cool in the hot environment it lives in. Flapping An elephant's is 2.5 cm thick and very tough. It protects the animal from insect bites. The skin is also very wrinkled. The wrinkles trap water, which helps keep the elephant cool. skin They can weigh as much as 14 000 pounds and grow up to 10 feet tall. The elephants is a combination of nose and elongated upper lip. trunk It is extremely flexible and strong, used to gather and lift food, grasp, carry, toss, sniff, shower, and snorkel. It is also used for . communication Most tusks are about 6 feet long and weigh about 50 pounds each. They are made of a valuable material called . When elephants are threatened, they point their tusks and charge to scare predators away. They are used for digging and carrying food, but not chewing. ivory Elephants are herbivores, and only eat plants. They eat mainly leaves, roots, grasses, bark, and many fruits. Elephants have bodies adapted to their habitats and lifestyles. Elephants live in the hot landscape, where climates stay warm year-round. equatorial There are 2 species of elephants African Elephant (Loxodonta africana) They are found south of the across savannas, jungles, and swampland. Sahara Desert Asian Elephant (Elephas Maximus) They are larger than Asian elephants. Asian elephants inhabit areas of southern and southeastern , in isolated forests and jungles. Asia Paleomastadons began to grow larger tusks, and a . The lineage dates back to approximately million years ago The paleomastadont, like most mammals, needed to stay hydrated and drink water. Platybelodon had small upper tusks and a large, flattened lower jaw. Proboscideans Paleomastadonts Platybelodon Modern day elephants came from an ancient line of mammals called 55 Ancestors gave rise to various branches as well as to the direct line leading to modern day elephants. The first Proboscideans were about the size of a pig and lived in Northern Africa 50 million years ago, called Moeritherium As its weight increased, its legs had to get longer to raise the body clear of the ground. Moeritherium weighed approximately 225 kg. Moeritherium had six small cheek teeth throughout adult life. As their size increased, elephants evolved larger teeth, including their incisor teeth as tusks. If elephant teeth had not evolved, they would wear out too soon and the animal would unable to chew its food. die of starvation , trunk To do so, it had 3 options: 1) Bend down on its knees and drink water like a carnivore, but in this position it would be highly
. vulnerable to attack 2) Carry its head on a long neck- but this would impose an impossible load on the musculoskeletal system 3) Keep head close to the body and develop a long tube to raise water next came the favoured the Paleomastadonts who were developing trunks, as they were less vulnerable to attacks. Natural Selection Survival of the Fittest The paleomastadonts beginning to develop trunks had an easier chance of survival. As a result, they were able to live to pass on their to future generations. genes Possible Ancestors Its lower jaw was used as a shovel, for rooting out marshy vegetation. Its flat lower jaw evolved to become shorter, to make room for a longer trunk. Primelephas (4-6 mya) (15 mya) (35 mya) (55 mya) Primelephas evolved into 3 species Elephas maximus Loxodonta africana Mammuthus primigenious The last mammoth species became extinct around 10 000 years ago, due to either climatic factors or as a consequence of hunting by early man. Natural selection favoured those with larger teeth as they were able to chew more food, without their teeth wearing out. Speciation Modern day elephants experienced divergent evolution Elephants have many relatives who all share a common ancestor. All of these mammals have evolved to become different types of herbivores. The hyrax is as a small, furry herbivore. It has a similar bone structure to that of an elephant. are herbivores who live in the sea. They are also related to elephants. Dugongs and manatees Elephants have experienced genetic bottleneck Widespread hunting severely reduced elephant populations in Africa by the early 1900's. Elephants were hunted for their ivory tusks. In 1930, of elephants were born without tusks. 1% the ivory hunters did not bother killing them because there was no ivory to recover. The smaller population of elephants passed along the alleles for
more frequently. "no tusks" The result:
As many as of the elephants in some modern populations have no tusks 38% Hunting elephants has caused genetic drift within certain elephant populations. Elephants experienced allopatric speciation African elephants and Asian elephants were geographically isolated as they migrated to different parts of the world. As a result, they evolved reproductive isolating mechanisms Each species of elephant has
isolating mechanisms prezygotic They have developed because they live in different parts of the world. ecological isolation Sexual Dimorphism There is a large degree of sexual dimorphism between male and female Asian elephants, as Adult females are about half the size of the largest males. Males grow longer tusks than females. The size of the males' tusks are used to attract females when mating. Tempo of evolution: Gradualism Elephants evolved slowly, over millions of years. They gradually developed traits, like their tusks and trunk, over many generations. Our Theory: Future Evolution of Elephants Elephants will have no tusks as a result of poachers hunting for ivory. As a result, elephants will not pick mates based on their tusk size. Elephants with tusks will be killed. Therefore, it will become easier for elephants without tusks to survive and pass on their genes. As a result of , temperatures around the world are increasing. global warming The result: Dumbo! Works Cited Nieson, Marc. Elephants. Minnesota: Creative Education, 2002. Crossingham, John. What is an Elephant?. New York: Crabtree Publishing Company, 2002. Savage, Robert J.G. Mammal Evolution. United Kingdom: Library of Congress Cataloging-in-Publication Data, 1986. Elephants will become smaller, as their food supply and living space will decrease. This will occur because humans are invading their habitats for their own needs. Sexual Selection: As a result, the smaller elephants will have beneficial adaptations as they will require less food and space to survive. There will be a decrease in due to the many elephants being killed.

The loss of "tusk alleles", rising temperatures, and need of space by humans will cause evolution to occur as a result of . natural selection biodiversity Tusks
Normal sized ears
Large size No tusks
Large ears
Reduction in size The genetic variation in the gene pool will decrease. Natural selection will favour elephants with larger ears, as they will be able to cool off easier. Gradualism: Elephants will continue to gradually evolve over time in order to acquire these traits. Intermediate species evolved and began to grow larger in size over many generations, because it was easier for them to fight off predators. Therefore, natural Selection favoured larger elephants. Quiz Elephants use their trunks for:
a) Drinking
b) Lifting objects
c) Showering
d) All of the above Elephant tusks are made of:
a) Cartilage
b) Bone
c) Ivory
d) Skin Elephants experienced:
a) Sympatric speciation
b) Divergent evolution
c) Adaptive radiation
d) Stabilizing selection Moeritherium weighed approximately...
a) 5 tonnes
b) 10 kg
c) 900 lbs
d) 225 kg What 2 species of elephants exist?
a) North American and Asian
b) European and African
c) African and Asian
d) African and Australian The last mammoth species became extinct around:
a) 10 000 years ago
b) 5 million years ago
c) 2000 years ago
d) 100 years ago Elephants share common ancestors with:
a) Crocodiles
b) Manatees
c) Turtles
d) Whales Elephants chose mates based on:
a) The length of their trunk
b) The size of their tusks
c) Their personality
d) The size of their ears Grabianowski, Ed. "How Natural Selection Works." How Stuff Works. Web. Wed. 24 Oct. 2012. <http://www.howstuffworks.com>
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