We all know the ancestors of whales are small land mammals, after starting to live in the ocean, they went through more than 50 million years of evolution and eventually became a family of marine mammals. have the most diverse and popular breasts today. The whale suborder includes not only giant blue whales, sperm whales, and bowhead whales, but also many different species of dolphins. Species in the suborder whales still exist on Earth today. The “whale” Pakicetus is one of the earliest known ancient whales, this animal that lived 50 million years ago looked like a dog with long limbs and fur. If you look closely at the Pakicetus whale, you will see that its nose is located in the front of the head, like today’s mammals. Because the nostrils of Pakicetus whales are located in front of the mouth, when swimming they will look like dogs today because underwater, they have to almost raise their heads out of the water when swimming. Pakicetus is an extinct genus of cetacea, found in Pre-Eocene rocks in Pakistan. The strata where the fossils were found were then part of the coastal Tethys Sea. .As the ancient whales gradually entered the ocean, their body structure began to evolve in a way that was adapted to aquatic life, including the position of the neck, the nostrils gradually moving to the top of the head, Below are pictures of the primitive whale (Protocetus) and a restored image of the Basilosaurus whale, both of which show their nostrils gradually turning upward. Protocetus is one of the most ancient whale genera, which lived in the middle of the Meridian period 45 million years ago near Cairo, Egypt. It was one of the first genera of whales to have fully adapted to aquatic habitats. They are quite small, only about 2.5 m long, on the body still keep the traces of limbs with fingers connected by swimming membranes with the hind limbs smaller than the front limbs. Jaws long, with sharp teeth. The front teeth are used to catch prey and the back teeth are used to cut meat. Unlike the older predecessor Pakicetus, which lived a semi-aquatic lifestyle, Protocetus was able to develop ear canals and hear underwater sounds (but it is unclear whether they developed sonar or sonar). not yet) and developed a flattened tail like today’s whales. Their nostrils are still located on the head, they still do not have a stoma on the top of the head and rely more on eyesight for food. Basilosaurus is one of the primitive whales that evolved from land mammals and later evolved into modern day whales. Basilosaurus averaged about 18 – 20 m long and weighed about 15 tons, once distributed in North America, North Africa and Central Asia and was considered the largest animal that ever lived in its time. The ancient whale species mentioned above all belong to the ancient whale suborder, the baleen whales and the toothed whales in the ocean today all evolved from the ancient whale suborder. They appeared in the middle Oligocene, about 30 million years ago. Compared to today’s whales, their appearance is quite similar to ancient whales, but the evolution to change the position of the nostrils took quite a long time – about 20 million years. Diagram of the evolution of ancient whales. Schematic diagram of the evolution of modern whales. Modern whales have evolved to move the nostrils from the front of the mouth to the top of the head. It’s not just a change of location. The esophagus and trachea of ​​today’s terrestrial mammals are interconnected, so if our noses are blocked by a cold, we can still use our mouths to breathe instead of our nostrils. In addition to breathing, our nose also has the function of smelling. But modern whales are different, and the changes in the position of the nostrils and the changes they made to aquatic life have caused the trachea and esophagus to separate. The nostrils connect to the lungs and the esophagus connects to the digestive system, so their noses are only used for breathing, not for smelling. The nostrils of modern whales located at the top of the head actually help them survive more effectively and safely than the holes in the front of the mouth when in the ocean. But even if their nostrils are at the top of their heads, when they dive into the ocean, their noses are still underwater, how can modern whales ensure that they won’t choke? In fact, under the nostrils of whales have a very strong muscle group, they can completely close their nostrils when diving, avoiding the risk of choking on water. The separation of the esophagus and trachea also ensures that modern whales will not choke on water while hunting in the ocean. Large nostrils of baleen whales. The nostrils of a blue whale when diving into the water. In fact, all baleen whales still have two nostrils, while toothed whales have only one. The jets that whales spit out of the water are not water in their noses, but rather accumulations of water remaining in the “pits” of the nostrils, which are formed under the action of sub-lower pressure. Ocean. This prevents water from entering the nostrils, improving the safety and efficiency of breathing. However, the water column due to the whale’s breathing process once brought them great danger. In the era of whaling, sailors often relied on these water columns to locate the schools of fish. elephants. Killer whales belong to the toothed whale subspecies with only one nostril. Gray whales belong to the subspecies of baleen whales that spray water with a pair of nostrils.

Giant water lilies in South America 2. Whale Shark: Whale sharks are the largest fish in the world, adults can be 20 meters long. Possessing huge weight but they are not harmful to humans. To see whale sharks, you can go to Gladden Spit marine reserve in Belize (Central America) from March to June every year, Ningaloo marine park in Australia from March to August, or Isla Holbox in Mexico from May to October. 3. Leatherback Sea Turtle: The Leatherback is the world’s largest tortoise and also an endangered species. When mature, they are about 2.5 m long and weigh 900 kg, looking like a small truck. To see this turtle, you can go to travelFlorida from March to July, on the Caribbean coast of Costa Rica from March to June and at the Shell Beach reserve in Guyana from March to August. 4. Eastern gorilla: The eastern gorilla (Gorilla beringei) is the largest and most endangered primate in the Red List. Compared to other gorillas, they are much larger with an average weight of 200 kg. They are found in the dense forests of the Democratic Republic of the Congo, Uganda and Rwanda. Another subspecies of them is the mountain gorilla found in Bwindi impregnable national park in Uganda. 5. African Elephant: The African elephant is the largest land animal in the world. Their body is 9.1 m long and weighs 7.5 tons. At birth, the baby elephant weighed 90 kg and was 1 m tall. Currently, the danger to African elephants is mainly from poaching for ivory. To see this species, you can go to travel Botswana (South Africa) – home to the largest number of elephants in the world (130,000 heads). In addition, many other countries in Africa such as Tanzania, South Africa, Gabon, Zambia… are also home to this species. 6. Rafflesia Flower: The rafflesia flower has huge red-dotted petals 1.2 m in diameter and an unpleasant smell of rotting flesh. However, this is characteristic of Sabah, Malaysia and Surat Thani province, Thailand. You can admire this exotic flower in the rainforests of Indonesia, Thailand, the Philippines and Malaysia… 7. Komodo Dragon: This world’s largest lizard retains the appearance of a prehistoric dinosaur. They average 3 m long and weigh 140 kg. The rare Komodo dragon is found only in Komodo National Park, a UNESCO World Heritage Site in Indonesia. 8. Red kangaroo: The red kangaroo is the largest marsupial in the world, as well as the largest animal on the Australian continent. As adults, they are 2 m tall and weigh 100 kg. The powerful hind legs allow them to jump 7 m high and move at a speed of 56 km / h. You can find red kangaroos in the arid regions of the continent in Australia, or in Mungo National Park. 9. Saltwater crocodile: This largest reptile in the world is an average of 6 meters long and weighs 1 ton. The swimming speed of this species is also terrible, up to 30 km / h, 3 times faster than the fastest athletes. Saltwater crocodiles can be found in Kakadu National Park and Nitmiluk National Park in Australia. In addition, when visiting many Southeast Asian countries and India, customers travel You can also see saltwater crocodiles. 10. Blue whale: The blue whale is the largest animal that has ever existed on Earth, far more than the dinosaurs in history. When adult blue whales reach a length of 33 m and weigh 200 tons, their heart alone is as heavy as a car. You can see this amazing animal off the coast of Trincomalee, Sri Lanka, from March to April, or in western Australia from May to December.