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This tree shows the relatedness of the organisms that are included in Order Cetacea. This tree also includes the inference that all members of Order Cetacea came from the same organism, and then slowly branched off, into the many different species of the modern day.

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The Common Dolphin would be an example of stabilizing selection because the modern dolphin evolved from the extreme and various traits, to the middle-sized dolphin that is shown today. The previous ancestors of the modern dolphin were long and big, or short and slim until the modern dolphin, which is a mix of both long and small.

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The Killer Whale would be an example of stabilizing selection because the average of all the phenotypes was the best fit for that organisms, causing them to beat out the extreme variations in their cousins. The whales that had a mix of each of the extreme variations, survived and did better than the other variations.

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The Blue Whale is an example of directional selection because the bigger whales beat out the smaller whales, which is the extreme variation. The whales would eat more food more sufficiently and they beat out the smaller cousins of them. The bigger the whale, the better survival rates of that whale.

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                                                                                                  Descent with Modification

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                                                                                                  Descent with Modification

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Descent with modification is the passing down of traits from parent to offspring. This theory is shown by Order Cetacea because as the species evolve and go through Natural Selection, these traits are passed down, making each organism a little different, which eventually will create the divergence in the order. The evolution of the hindlimbs is an example of descent with modification because as time went by, the use of these hindlimbs were decreasing. This action caused the slow decrease of the presence of these bones, and the slow increase of structures that were necessary for these organisms to swim well. Another example of descent with modification in Order Cetacea is evolution of the blowhole. The blowhole is a structure in Cetaceans that allows them to breathe, and in the earliest organisms, there was no evidence of a structure like so. When the Cetaceans started their movement to water mammals, the creation of a structure like this was necessary. All of these structures and traits that were passed down, caused the divergence in Cetaceans, which lead to new species and new traits and structures as well.

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Examples of microevolution in the Killer Whale is the presence of sharp teeth. This helps the Killer Whale to rip and chew their prey. The other exemplary organisms in my taxonomic group do not have very sharp teeth, which shows this difference between the three.

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An example of microevolution in the Bottlenose Dolphin is their adaptations for diving. During a dive, blood is pushed away from tissues tolerant of low oxygen levels toward the heart and brain, which require a constant supply of oxygen. This need for oxygen is supported by the proteins found in the dolphin.

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Examples of microevolution in the Blue Whale include baleen plates, that can only be found in whales, and in none of my other two species in my taxonomic group. Baleen plates are a filter-feeder system inside the mouths of baleen whales. The baleen system works by a whale opening its mouth underwater and taking in water. Baleen is similar to bristles and consists of keratin, the same substance found in human fingernails and hair.

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Name of fossil: Basilosaurus Cetoides
Age of fossil (give time period as well): Late-Eocene, about 40-35 million years ago

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Reproductive isolation impacts the organisms included in Order Cetacea because there is no gene flow. This is caused by the fact that they are not interacting with any other groups besides their migratory group. They have a very shallow gene pool and that impacts these animals by having little to no variations. One species is not interacting with another migratory pod of the same species.

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The species included in Order Cetacea follow divergent evolution because they all evolved from a similar ancestor, like the Dorudon. The Dorudon has common structures to the modern day organisms, but it also included different traits that did not prove to be beneficial to the future organisms. Divergent Evolution is when parent organisms create an organism, and as time goes by, the organisms diverge into different species. These organisms share similar structures which gives evidence as to how they are related.

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I believe that the evolution that my organisms follows is the gradualism process of evolution because all Cetaceans evolved from land animals. The process of evolution for my three exemplary organisms started with land mammals, one of those being a Pakicetidae. This is proven through the presence of hip bones and other parts of bones that land dwelling mammals use in order to walk. This process happened over a long span of time, and through that, the organisms would gradually get closer and closer to water, and evolve into the organisms present today.

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The Killer Whale and the Bottlenose Dolphin both have the same number of chromosomes, which could show some type of evolutionary relationship between order Cetacea. Studies have also shown that the number of genes between whales and dolphins are only a few off, proving their similarity. These similarities show that these species might have a similar ancestor, meaning that they might have come from the same early organism. If these organisms came from the same ancestor, this would mean that the organisms had to branch off into the different species available today. This divergence would cause the number of genes to increase or decrease from that original number, because of the new traits presented. This would also prove the amount of similarities in different structures.

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Breakdown of the Hearing System of Cetaceans:

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Breakdown of the Hearing System of Cetaceans:

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An example of evolution in Cetaceans involves the incus. Scientists have examined this small ear bone, and they concluded that in shape and proportions it is intermediate between the equivalent bone in modern Cetaceans. Though modern Cetaceans have the same basic hearing apparatus as all other mammals, it is adapted in a unique way for hearing underwater. Pakicetus provides a snapshot of the transition. The flipper of a dolphin or whale are homologous structures. They are different and have a different purpose, but they are similar and share common traits. Another example of similar anatomy in early and modern Cetaceans is the presence of a vestigial hindlimbs. This shows that the ancestors of all Cetaceans had to have come from an organism which needed the ability to walk, or use their legs in order to survive. This discovery gives evidence for the modern Blue Whale to be related to the Pakicetus, and many more. The Blue Whale, and other Cetaceans do not use this hindlimb. Since the evolution of their shape and fins, they are capable of swimming around in the water without hindlimbs. This also shows the importance of these hindlimbs over time, because the hindlimbs and other bones associated with that, were not beneficial, which is why only small bones are still present in the modern Cetaceans.

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Each of these fossil examples show different Cetaceans at different time periods. The earliest Cetacean shown here, the Pakicetus, has a long head, and was a land-dwelling mammal. The most modern fossil shown, the Aetiocetus, was a marine organism. There are many similarities in these two organisms, including head shape, and body form. The Aetiocetus evolved from the early Pakicetus, and this can be proven by their many homologous structures. The modern Cetaceans evolved from both these organisms, and this is proven through the presence of hind limb bones in the modern species.

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Name of fossil: Aetiocetus

Age of fossil (give time period as well): Late-Oligocene, from 33.9 to 23 million years ago

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Name of fossil: Dorudon atrox

Age of fossil (give time period as well): Late-Eocene, from 35-38 million years ago

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Name of fossil: Zygorhiza
Age of fossil (give time period aswell): Late-Eocene, about 40 million years ago

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Name of fossil: Remingtonocetidae

Age of fossil (give time period as well): Middle-Eocene, about 47-48 million years ago

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Name of fossil: Pakicetus inachus

Age of fossil (give time period as well): Early Eocene, about 50 million years ago.

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                             Order Cetacea

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                             Order Cetacea

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The external characteristics of all Cetaceans include a large, fusiform shaped body, no hair and no sebaceous glands, tails flattened into flukes, forelimbs that are modified into flippers, and vestigial hind limbs. These characteristics are what makes the organisms included in the Order Cetacea, so different from other taxonomic groups. Cetaceans normally feed and travel together. Play is a common behavior, especially among young organisms. Play allows these individuals to practice and perfect behavioral patterns, such as aggression, that will be socially useful later in life.  Aggression is also an important behavior among Cetaceans and is seen in normal herd behavior and feeding. Mating behavior includes biting as one of the ways that the males compete for the females. Cetaceans start biting and raking the teeth over another male also, and this shows their power over that other male. Courtship involves physical and acoustic displays, such as the elaborate songs of male humpbacks, and leads to contact with the flippers and other parts of the body. Successful courtship culminates in mating. These behavioral specific characteristics also are what makes these organisms unique and different to other taxonomic groups. Cetacean species are marine, inhabiting coastal areas as well as the open ocean. Cetaceans inhabit all of the world's oceans, as well as some freshwater lakes and rivers in South America, North America, and Asia.

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Delphinus delphis
External Characteristics:
Common dolphins are colorful, with a complex crisscross or hourglass color pattern on the side, while the long-beaked common dolphin being more muted in color. There are large dark circles around the eyes connected by a dark line that runs across the head behind the beak and a black stripe runs from the jaw to the flippers. The dorsal fin is pointed and located near the middle of the back and is black-to-light gray in color with a black border. The flippers are long and thin and slightly curved or pointed depending on geographical location. Flukes are thin and pointed at the tips with a slight notch in the center. Common dolphins can reach lengths of 7.5 - 8.5 feet and weigh as much as 300 lb.
Behavioral Characteristics:
The Common Dolphin is very social, and they live in large groups called pods. The number in a pod can be several hundred or it can be in the thousands. They have a very complex hierarchy that keeps them orderly and they tend to create subgroups based on age and other factors. They are very active and they seem to be able to move through the water almost effortlessly. They are also playful so they spend time teasing each other. Touch and echolocation are big parts of their social interactions with each other. Vocalizations including whistling, whining, and clicking are very common.
Habitat Specific Information:
The Common Dolphin lives in bodies of water that have a warm temperature. These dolphins live in places where food is abundant and the water is warm. They live in coastal regions from the Mediterranean, to the waters near Australia.

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Orcinus orca
External Characteristics:
Male Killer Whales have larger features than the females including pectoral flippers, dorsal fins, and tail flukes. They have a cylindrical body shape, efficient for swimming. They also have black and white coloring, with a gray patch called a “saddle” on the back behind the dorsal fin. At full maturity the male Killer Whale will usually grow to an average length of 20 – 26 ft. long and weigh an average of 8,000 lbs. – 12,000 lbs. while an adult female Killer Whale will grow to an average length of 16 – 23 ft. long and weigh between 3,000 lbs. – 6,000 lbs. Depending on the pod the Killer Whales belongs to, their dorsal fin may either be long, tapered and pointed in a triangular fashion or rounded and curved towards the end. The skull is somewhat oval shaped and the beak is extremely short and rounded at the end. To assist with swimming the flippers are paddle shaped with rounded ends and the flukes are tapered back and pointed at the end like a wide triangle.
Behavioral Characteristics:
Killer whales travel in pods, and the pods are very unstable, but killer whales are very social organisms. When it comes to socializing with one another, communication typically involves using a series of clicks and whistles to inform other organisms of important information. The amount of vocal communication that occurs between a group of killer whales varies from one pod to the next. Communication may also occur using physical gestures such as light touches, jumping out of the water, lunging, charging, lob-tailing or spy-hopping. The combination of verbal and physical communication allows these marine mammals to display a wide range of interests, wants and needs to one another.
Habitat Specific Information:
Since the Killer Whale has the ability to adapt in many climates, they are called the most widely distributed mammal. They either live in the warm water near the equator, or the icy waters near the North and South poles. Killer Whales live wherever food is abundant.

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Internal Charcteristics of All Cetaceans 

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Internal Charcteristics of All Cetaceans 

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The internal characteristics of Cetaceans include being warm blooded, which accounts for the arteries and veins in the tongue of the whales, to act as heat exchangers to help conserve body heat. The blubber layer in Cetaceans isn’t just for insulation in cold waters; it also stores energy when the organism isn’t eating, and it helps keep the organism buoyant. Whales, and other organisms that need to dive for food, have a flexible rib cage. When diving to deep depths, it easily bends under pressure without breaking. The flukes are controlled by a massive muscle system in the peduncle.

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Balaenoptera musculus
External Characteristics:
The weight of an average Blue Whale is up to 330,000 pounds, and the length is up to 110 feet, depending on location. Their appearance is a long body with mottled gray color pattern that appears light blue when seen through water. All whales are mammals and so that automatically tells us that they need to breath in air to fill their lungs. The anatomy of a whale is designed to allow it to easily move through the water. The back end of a whale is where you will see the dorsal fin. This is in place to help a whale remain balanced. Since it can be very cold in the waters where a whale lives, they need plenty of insulation. They get it in the way of what is called blubber. This is underneath the top layer of skin. The size of the heart of a whale will depend on what species it is. They also have vertebrae that are fused to the neck. It is this design of the whale anatomy that allows them plenty of flexibility in their movements throughout the water.
Behavioral Characteristics:
The Blue Whale doesn’t travel in groups, being called the loners of the ocean, but most of the time you will see a mother and her baby, or the occasional large group of blue whales when there is an abundance of food. They perform births in water, and they usually do not travel with mates.
Habitat Specific Information:
Blue whales are found worldwide, from subpolar to subtropical latitudes. Poleward movements in spring allow the whales to take advantage of high zooplankton production in summer, which is one of their main sources of food. Although Blue Whales are found in coastal waters, they are thought to occur generally more offshore than other whales.

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The embryo of Cetaceans develops a number of features that it later abandons before it attains its final form.  Many organisms, while still in the womb, begin to develop body hair. Yet no modern species retain any body hair after birth, except for some snout hairs and hairs around their blowholes used as sensory bristles in a few species. The fact that whales have the genes for producing body hair shows that their ancestors had body hair. In other words, their ancestors were ordinary mammals. In many embryonic whales, external hind limb buds are visible for a time but then disappear as the whale grows larger. The whale embryo starts off with its nostrils in the usual place for mammals, at the tip of the snout. But during development, the nostrils migrate to their final place at the top of the head to form the blowhole.

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The protein Myoglobin is crucial in Cetaceans because it basically enables them to dive under water. Myoglobin, along with Hemoglobin, stores oxygen in the body tissue. This protein helps these organisms to conserve oxygen while diving. Cetaceans need to dive in order to get food, so this trait is very important for them in order to survive. Lipids are also important in Cetaceans because it provides the blubber necessary for these organisms to live. Depending on the species, the thickness of the blubber can vary dramatically from 1 inch up to 11 inches thick. While the thickness of the blubber can play a role in determining what climates a marine mammal can comfortably live in, the blubbers' lipid concentration is much more important for maintaining body heat than how thick the layer of blubber is. The higher the lipid concentration is in a whale’s blubber the better it is at maintaining body heat while the higher the water concentration is the less effective the blubber is at insulating internal heat. The use of blubber is extremely important for keeping vital organs warm and functioning properly, especially since whales live in the ocean which can be several times colder than air. This becomes even more apparent in the coldest regions of the world such as the Arctic and Antarctic waters. This supports evolutionary relationships within my organisms because all of the organisms included in the Order Cetacea have these proteins and these lipids in order to preform necessary tasks for survival.

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Common Name: Blue Whale
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Cetacea
Family: Balaenidae
Genus: Balaenoptera
Species: Musculus
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Common Name: Killer Whale

Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Cetacea
Family: Delphinidae
Genus: Orcinus
Species: Orca
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Common Name: Common Dolphin
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Cetacea
Family: Delphinidae
Genus: Tursiops
Species: Truncatus

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Taxonomy alone can show the information regarding the relatedness of different species by the fact that the different species have the same taxonomic classification until the Family taxonomic classification. Even two of my exemplary organisms belong to the same family, which also shows their relatedness. Since they have these similarities, this shows that they might have come from a common ancestor, which would also infer similarities in the body structure and behavior.