Suborder Mysticeti (Baleen Whales)
Suborder Odontoceti (Toothed Whales)
Whales are amongst the largest animals in the world. Most whales can grow to be up to 18 meters long and weigh at least 70 tons. The largest animal is the Blue Whale, whose body length can be up to 110 feet long and can weight up to 200 tons. Whales can be found almost anywhere. The Sperm whale has the largest brain of any animal in the animal kingdom.  The major difference that is used in classifying whales is where they have teeth or baleen plates, besides that whales are alike in almost every way. Whales are very gentle creatures that do not pose any real threat to man. Whales have been hunted by people for their meat and blubber. Some species of whales are endangered. Actions have been taken by the IWC to prevent the extinction of whales.
The main difference in most of the cetaceans is if they have teeth or baleen plates. These are divided into 2 families: Odontoceti(Toothed Whales) and Mysticeti(Baleen Whales). The Odontoceti family contains the sperm whales and the beaked whales as the Mysticeti family contains right whales, bowhead whales, gray whales, and many others. The color of most whales depends on the sex, age, and location. To keep warm, whales depend on the blubber that surrounds their bodies. In some species the layer of blubber can be up to 20 inches thick. Whales do not have nostrils to breathe through as we do, buy instead they use their blowholes. The blowhole is located very close to the top of the head so that it does not have to completely get its head out of the water to breathe. Baleen whales have 2 blowholes which are located parallel to each other. Unlike baleen whales, toothed whales only have one blowhole. As the whale submerges itself muscles near the blowhole close it so that when it dives water does not enter. Most whales have a dorsal fin which is used as a stabilizer for its swimming. Whales possess a four chambered heart as humans do and the neck vertebrae of most whales is fused, which allows for a more stable swim. 
Whales usually mate in tropical waters. The female whale will have a baby usually every one to three years. The mother will carry the baby for 9-18 months before giving birth and the baby whale, or calve, is able to swim as soon as it is born. Whales are viviparous mammals, which means that the mother nourishes the baby, through an umbilical cord, as it is still in the womb.After the birthing, the calf will have a belly button. The mother will nurse the calve with milk, and the nursing time can last more than 1 year in many species. The mother whale feeds her baby by spraying thick milk into its mouth. The reason that the milk is very think is so that as it does not dissolve in the water. The whales reproductive maturity happens later in the whales life, usually when the whale is seven to ten years old. When the baby whale is born, it comes out tail first. This is so that the baby does not drown as it enters the water. When the male whale is swimming, it brings its genital organs up into its body cavity so that it will be able to swim smoother and faster. After whales mate they usually don't stay with their partners. It is quite common for a female whale to have more than one mate during each season. 
Suborder Mysticeti contains whales known as baleen whales. These whales do not have teeth but instead contain baleen plates that are used to filter plankton and other small fish out of the water. Suborder Odontoceti contain the toothed whales that feed on small fish and other mammals.
- Bowhead Whale
These whales can be located in the arctic region living among icebergs and freezing water surfaces. Groups of up to 14 whales at once are seen feeding together. The groups usually travel in a V shape. It is not unusual to see a pod of 3 whales. This group is made up of 2 whales(usually partners)and their calf. They will stay together for a few weeks before joining another group. More whales will join a group during migration. The age of mammals can be determined by a close examination of their teeth, but baleen whales do not have teeth so figuring out their age can be rather difficult. It has been said that Bowhead Whales are one of the oldest animals in the world. The means of discovering this was the finding of the tips of stone harpoons and an eye tissue analysis. It is believed that they can grow to be more than 100 years old. Due to living in the arctic Bowhead Whales must have a thick layer of blubber to survive. One Bowhead Whale can eat up to 100 tons of crustacean a year.
- Gray Whale
Gray whales prefer eating food that is found close to the floor of the ocean. They do not stray far from the coast when they're feeding. Once they reach about 8 years they are considered sexually mature. The new born baby is able to swim right after birth and it does not take long for the its weight to double. The calf does not wander far from its mother but spends most of its time staying very close to her. Gray Whales are known to breed every 2-4 years. Mating usually happens during the winter and the pregnant mothers return to the feeding locations in the summer and later are seen trekking back to the breeding grounds during the winter. 
It is safe to say that the biggest threat to whales is the continual hunting of them. There has been many successful attempts to stop or at least limit the number of whales that are able to be hunted and killed. The moratorium issued by the IWC stills allows other countries to continue their usual killing of whales. The amounts of food that is left for them to eat is also a threat on whales. The continual climate change of the water in the antarctic are responsible for the decreasing population of krill.  Below are two examples of whales and the threats they face.
- Bowhead Whales
Bowhead Whales are hunted for their blubber, oil , baleen, and meat. They are an endangered species. Other things contributing to the health of Bowhead Whales is the loss of their homes. They live in the Arctic where many pollutants and toxins. These toxins can damage the Bowhead Whales internal systems. Some Native Americans are able to hunt only a limited amount of whale and this is helping keep the population balanced. 
- Sperm Whales
Sperm Whales are the prey of hungry killer whales. Other whales have also been seen bothering them but none are as great a threat as large sharks. Large sharks are able to kill a baby sperm whale with ease. Even with all these the greatest threat to Sperm Whales has always been whaling. Between the years of 1800 and 1987 an estimated 1,000,000 whales have been hunted. The hunting of these Sperm Whales stopped due to the IWC in 1988. Sperm Whales are also harmed by on sea operations. These do not harm Sperm Whales as much as they do other whales that tend to stay close to the coast. 
- Whale Reproduction Animal Corner
- Whale Anatomy Andrea Vanessa & Erica
- Anatomy whale - Origins and taxonomy, Anatomy, Behaviour, Whales in culture
- whale - Origins and taxonomy, Anatomy, Behaviour, Whales in culture State University
- Bowhead whale - Ecology & Habitat by the World Wildlife Fund
- Gray whale - Ecology & Habitat by the World Wildlife Fund
- Bowhead whale - Threats by the World Wildlife Fund
- Sperm Whales (Physeter macrocephalus) by the National Oceanic and Atmospheric Administration
- Whale Whale Order Cetacea by Defenders of Wildlife
- Blue Whale Facts - The Biggest Whale Whale Facts
- Whale Facts You Should Know by ThinkQuest