Whales Evolution

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?

I believe the Ambulocetus was the first organism in whale evolution to live primarily in the water, this is due to the fact that the Ambulocetus whale had a hard time staying on land due to its weak legs that could not support its heavy body.

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.

Long ago, native tribes, from many places in the world, depended largely on whales for protein in their diets. They were also able to use much of the whale for oil, thus began a tradition of whaling. The first documented whaling expedition occurred in South Korea

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

can be 22.5 feet, and their tanks are around 150 feet long. Also, the whale can get diseases.

It’s a average, nice summer day and you and your family decide to see killer whales at SeaWorld. Once you arrive to the place and see the large animals in the tank you’re fascinated by their large size. Killer whales, or orca whales, are large marine mammals that can be found in every ocean around the world. They can swim for hundred of miles and “routinely dive up to 300 ft” (“Should Orca Whales Be Kept in Captivity”). They also live in large family groups known as pods that they will rarely ever leave. Seeing these large animals in the tanks that they make seem small due to their large size and with other whales along with marks, mainly bite marks and flopped over dorsal fin for the males, make it questionable if they even should be here and if these other whales are family in the seemingly makeshift pod. Orcas should not be in captivity because of health problems, lack of space in the tanks, and most of them are taken from their homes in the wild where their true family is.

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.

Whales in captivity are held in swimming pools that are barely bigger than they are. According to Melissa Sawyer, “In the wild, they can easily travel 50 to 100 miles a day. However, in captivity, a typical tank is only twice their size, forcing the animals to swim in small circles or float aimlessly.” (Sawyer 1). Imagine living your whole life inside a bathtub, that is how whales that are in captivity feel. Due to their small living

Male killer whales typically live up to 30 years in the wild but can live for as long as 60 years. Female killer whales typically live up to 50 years but they can live as long as 100 years (“Killers”). In captivity, only a few out of the more than 200 whales that have been either captured in the wild or bred at the marine parks have lived beyond 40 years (Rose). Female killer whales become sexually active between 6-10 years of age and males between 10-13 years of age. Female killer whales in the wild are thought to breed every three to five years and nurse their calves for the first one to two years. The gestation period for the pregnancy is seventeen months (“Welcome”). Killer whales are very social animals and are commonly found in pods of as few as 3 to more than 25 animals including at least one large male. Killer whales typically stay in their pods for their entire lives. Various pods of killer whales have been observed mixing with other pods either for social interactions or mating (“Killer”). They communicate through a series of whistle and clicks, which can be modulated by pitch and multiple harmonics. Pulsed calls are the most common form of vocalization that resembles squeaks, screams, and squawks to the human ear (“Killer”). Killer whales are actually pack hunters, like wolves, coordinating their attack and herding their prey into a small area. They are called killer whales due to the fact that

As mammals, they also give birth to a live animal, called a whale calf. Unlike humans, who can take around one year to learn how to walk, whale calves are born already able to swim.

Dolphins have been around a lot longer than humans. They originated about 50 million years ago. The most common dolphin, being the bottlenose dolphin, has been around for 15 million years. Surprisingly, dolphins originated from members of the cetaceans group. Cetaceans used to be land mammals but evolved into being aquatic mammals. In From Land to Water it stated, “The transition from land to water is documented by a series of intermediate fossils from India and Pakistan.” This research helps prove how they used to be land mammals but evolved to live in the ocean. Dolphins are one out of many aquatic mammals who need oxygen, but they need water in order to live. Believe it or not, dolphins are somewhat related to hippos, camels, deer, cattle, and giraffes. In From Land to Water, “ Many features that are

They move by swinging their tails. Though they are heavy , they move quickly. In winter , they will swim from the Arctic Ocean to the South Pacific . In South worm sea area, whale mother gives birth to whale baby. Then in summer, they will return their home.