Evolution Of Whales

Why Whales Lost Their Legs Kiara Rojas Honors Biology INTRODUCTION Millions of years ago, whales had legs. Pakicetus, the first whales, were land animals. Pakicetus does not resemble the whale at all from the outside but, they share a similar ear region that is unlike those of any other mammal. This discovery provided evidence that Pakicetus and whales are linked. The question is, why did whale lose their legs?

Which fossil organism in whale evolution do you think was the first to live mostly in water? Explain your claim with evidence and reasoning.

The evolutionary path of a whale is a fascinating process of a terrestrial mammal that evolves into a marine mammal. This evolutionary path started with one of the earliest ancestors called “Pakicetus”. A Pakicetus was discovered to be a land animal with four legs that had teeth as carnivores. It skull structure was long, but this organism didn’t look like any marine animal. The scientist then discovered that on the skull’s ear region it was surrounded by a bony wall. This feature on an organism only was distinct from one type of species, scientist discovered that this animal “Pakicetus” was an ancestor of a whale. By comparing the early whales Pakicetus to the next generation of ancestors Ambulocetus, the Ambulocetus whale looks more like

The origin of modern day whales, a mystery that has puzzled paleontologists for years, may have just been solved with the discovery of an ankle bone. This discovery might sound simple and unimportant, but the bones of these ancient animals hold many unanswered questions and provide solid proof of origin and behavior. The relationship between whales and other animals has proven to be difficult because whales are warm-blooded, like humans, yet they live in the sea. The fact that they are warm-blooded suggests that they are related to some type of land animal. However, the questions of exactly which animal, and how whales evolved from land to water, have remained unanswered until now.

In the 1930s, a strange bone was found on the shore of the lake by Oscar Frederickson. The bone was believed to be a spinal vertebra. Sadly, the original bone was lost in a fire, but a wooden copy was made. The bone was showed to Dr. James McLeod of the University of Manitoba, who felt it resembled a vertebra. However, he felt it was the vertebra of a whale-like creature that had been extinct for over four million years.

The Orrorin tugenensis was found with thigh bones. And the Orrorin tugenensis had small teeth like the Australopithicus.

First, the author asserts that being the kind of creature with so much mass, Brachiosaurus needed long legs to support them on land, yet the buoyancy would help share this burden. In the lecture, however, the professor indicates that Brachiosaurus were able to walk on land with the fossil tracks of such creatures

Killer whales are one of the most fascinating displays of ocean life. The killer whale has characteristics that are important to its survival in the ocean. It is interesting to know that killer whales have a plentiful diet. It is astounding to see how killer whales behave in the ocean. I plan to tell you about the killer whale, its characteristics, its diet, and its behavior in the ocean as well as the predation of the orca.

Recent evidence suggests that whales may not have always inhabited the oceans. Bones of an ancient ancestor of modern day whales, the Basilosaurus, were discovered in Pakistan that suggest whales evolved from a wolf-like creature. This genus of an early whale lived 34-40 million years ago in the late Eocene. These fossils show many different features in common with both modern day whales and modern day land mammals. Since the discovery of these bones, many other evidences show that whales are a likely descendant of the Basilosaurus through many different ways, such as embryologic comparison and DNA testing. Whales aren’t the only suspected descendants

In marine mammal biology a large portion of the study is dedicated towards the study of adaptations to the marine environment. By comparing the anatomy between marine mammals and terrestrial mammals scientists can better understand evolutionary history of how these two categories of mammals diverged from one another. The purpose of this lab was to study the anatomy of different marine and terrestrial mammals and compare their similarities and differences in homologous traits and how adaptations were made specifically for marine mammals to survive the aquatic environment. To accomplish this bones of different species of animals were studied since these structures serve as the basis for comparison across species as well as an indicator of each animal’s individual morphology and physiology. A standard measurement protocol for bones of particular regions of the skeleton was established with emphasis on length versus width ratio as well as it’s overall size relative to its more complex features, i.e. humerus length versus hand length.

The first ancestors of whales lived on land. They had feet instead of fins and quite often had individual toes. From their fossils we can gather that they spent most or all of their time on land. Mesonychids and Pakicetus more resembled dog or wolves then whale for they rarely went in the water, only near the shores for food. Whereas Ambulocetus was more like a crocodile; swimming in the water easily and basking on the shores. A few million years later the wales closer relatives appeared. Basilosaurus and Zygorhiza fossil were found near or in water. From this we can conclude that they lived in the shallow water of the oceans much like whales today.

The ocean is a vast biome that is constantly changing. There is much to learn about the life within, the article “Omura's whales (Balaenoptera omurai) off northwest Madagascar: ecology, Behavior and conservation needs” showed how our knowledge of the ocean and the life within continues to grow. Balaenoptera omurai, or Omura's whale was only found as a new species in the year 2003. Their are no dependable population size estimates or evaluation of conservation facts because there is not enough data collected on these cetaceans. Scientists are able apply what they learn from some of these organism to humans. In the article “Reproductive Conflict and the Evolution of Menopause in Killer Whales” scientists were able to draw comparisons between Humans and other species.

Without a strong long distance swim, a whale’s dorsal fin becomes weakened and will eventually either look bent, curve to the side, or break off.

In the article, “Sperm Whales and Killer Whales with the Largest Brain of All Toothed Whales Show Extreme Differences in Cerebellum” the author Sam H. Ridgway studies the cerebellums of the most widest distributed whales in the world. The killer whale and the sperm whale both have huge brains, but this study suggests why the killer whales have a significantly larger cerebellum than that of the sperm whale. After collecting, measuring, and preserving the species, the skull was ready to be chipped away and the brain ready to be taken from the massive cranium. Once extracted, the brain was measured to determine the cerebellar volume: (length of cerebellum base × width of the base × height × 1/3).

The fossil record is evidence of evolution. Fossils are often fingerprints of evolution. They help scientists track how species evolved