CH - Evolution (Elephant & Butterfly)


Elephants are giant land mammals that mostly live in areas in which water and food sources such as grass, fruit, small plant could easily found. A large number of elephants live in South Africa and South Asia that geographically are close to each other. In elephant anatomy, a big trunk -which is used for drinking water more easily- and two tusks - which function as protecting tools against the predators- and two extremely large ears that increase the surface area for heat loss could be observed as specific features of a full growth elephant. Elephants breed through sexual reproduction and have the most extended gestation period of all mammals. The gestation period in elephants is roughly 640 to 660 days.

The butterfly is considered as a flying insect that can found in many different kinds and colors of wings. Butterflies live in almost every area on the earth where it has suitable conditions. Favorable areas for butterflies are the ones in which enough food sources such as flowers could found. Open fields, jungles, plains, etc, could meet their needs to survive. Even though there are many different kinds of butterflies living on the Earth, they all have pretty much the same anatomy with the same functions. What makes butterflies distinctive comparing to other insects is that they have two wings each consisting of hindwing and forewing in which veins have existed, two compound eyes that increase their field of view, antennas that function as sensory appendages. Reproduction process in butterfly consists of a cycle with four stages. Reproduction timeline starts with egg, larva, pupa and ends with an adult butterfly.

Elephants belong to the Elephantidae family and to the Proboscidea order that includes a diverse group of animals including elephants, hyraxes and sea cows. Evolution of elephant started about 37-35 million years ago from a species known as “Moeritherium.” Moeritherium was heavily built animal and were about 3 feet tall. The skull shape of Moeritherium shows that they did have a trunk but not just as long as the elephant. After Moeritherium a species called “Barytherium” appeared. The most important feature that changed from the Moeritherium was the small tusks that used to grow on the upper and lower jaw of the Barytherium. This change was occurred to comply with their need which was cropping plants. About 26 million years ago, came the "Numidotherium" with much slender body shape. However, the Numidotherium grew over time, and its limb, skull, teeth and tusk size increased. These increments eventually lead to the appearance of a new species called the “Deinotherium.” The Deinotherium resembled the modern elephant, but it had downward curving tusks attached to its lower jaw. By the time the Deinotherium evolved into species known as the “Mammoths” about 1.6 million years ago. The Mammoths were the common ancestor between the Woolly Mammoths and modern elephants.

(I couldn’t find any evolutionary info about butterflies) The diversity of the butterfly wings in different areas is occurred due to the natural selection and also the adaptations. Butterflies are so large and attractive for predators. However, they developed some techniques to hide from those predators and protect themselves. For example, in Oklahoma, jungle butterflies have become very camouflage which helps them to blend right in on the forest. Carolina Satyr butterfly resembles a brown leaf in addition to resembling a few eye patterns on its wings to keep the predators such as birds. Birds are very nervous creatures. They are always scared of being hunted by a bigger bird, so these eyespots on brown butterflies would mimicry a predator which keeps the birds away. These changes due to the natural selection on the wings of butterflies have taken place over time which has resulted in evolution.

The line of descent shows that the Elephants have evolved in a result of divergent evolution. For demonstration, both elephant and woolly mammoth share a common ancestor and yet evolved into two different species.

Butterflies have evolved in a result of convergent evolution. Regarding the anatomy of butterflies, birds, and bats it can be obtained that all different tree species have wings that allow them to fly; but they do not share a common ancestor with wings. In all three examples, each one evolved to have wings independently which means that the evolution converged on a similar trait in vastly different species, so their wings are not due to having a common ancestor.

The Elephants use a vocal call to attract the Females that are also ready to mate. Occasionally male elephants fight with another male of the same species over a female during an intrasexual selection.

The Butterflies use a synthetic hormone called pheromones at close range which attracts the female. They also attract females with their wing patterns.

What make elephant and butterfly reproductively isolated are mechanical isolation -as both species have different arrangements of reproductive structure- and behavioral isolation - as both species have different methods to attract females.

“Theodosius Dobzhansky was born on January 24, 1900”(Scoville, H) He was a prominent Ukrainian-American evolutionary biologist and geneticist. Dobzhansky established the theory that natural selection is occurred in result of DNA mutations over time and redefined the term “evolution” in genetic terms as “A change in the frequency of an allele within a gene pool”(Scoville, H) He studied fruit flies in “population cages” and compared the changes in population with the idea of natural selection that was noted by Charles Darwin. ”In 1937, Dobzhansky wrote his most famous book Genetics and the Origin of Species.”(Scoville, H) His book was the first book that correlated the field of genetics with Charle Darwin’s book.

As climate change was the reason of the extinction of mammoths and other species that shared a common ancestor with elephant, climate change could affect the survival of elephants and cause extinction. “In 2002, a severe and sudden storm killed close to 80 percent of the overwintering monarch population in Mexico.”(EDF) Sudden climate changes could cause the decrement of butterfly populations. The persistence of both butterfly and elephant against climate change regarding their size which is very different compared to one another can be predicted as the species with the smaller size (butterfly) would become extinct first.

The digestive system of elephant consists of a mouth, Esophagus, stomach, liver and pancreas, Intestine, cecum, and rectum. Tree barks are the favorite food source of elephants. Tree bark contains calcium and roughage which aids the digestion tract. The digestive system of butterflies is made up of a tube which divided into three simple sections, the foregut, the midgut, and the hindgut. The foregut has a section called “Crop.” The crop is where the food is stored and becomes ready for the next section in which absorption and digestion occur. The butterflies drink nectar from flowers. Nectar is a sugar-rich liquid which gives butterflies all the nutrients they need. The difference between the digestive system of the elephant and the digestive system of the butterfly is that the digestive system in butterflies contains a cavity called Crop. Also, the digestion and absorption occur in the same section of the muscular tube of the midgut.

The respiratory tract in elephants has two sections, the conducting portion, and the respiratory portion. The conducting portion consists of nasal tubes, external nares, internal nares, pharynx, larynx, and trachea. The respiratory portion consists of bronchi, bronchioles, alveolar duct, the alveolar sac in the lung. The respiratory tract in butterflies consists of spiracles, tracheae, and air sacs. The function of trachea differs in elephant and butterfly. In the elephant, the trachea functions to transport glasses to the lungs, unlike the butterfly. The trachea in butterfly functions as same as the lungs, in which it could transport gasses to the cells of the whole body.

The circulatory system in elephants is closed and consists of the heart that pumps the blood throughout the body and the veins, the arteries, the capillaries and the lymphatics. The circulatory system in butterflies is opened and consists of a Tubular heart, ostia, lateral vessels and anterior vessels. One of the major differences between vertebrates such as elephant and insects such as butterfly is that is that the vertebrates have a transport medium known as blood while insects have a transport medium called hemolymph heterogeneous fluid. The other difference between elephant and butterfly is that all insects lack veins and arteries.

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