Learn About the Sirenians

Learn About the Sirenians Sirenians (Sirenia), also known as sea cows, are a group of mammals that includes dugongs and manatees. There are four species of sirenians alive today, three species of manatees and one species of dugong. A fifth species of sirenian, the Stellars sea cow, became extinct in the 18th century due to over-hunting by humans. The Stellars sea cow was the largest member of the sirenians and was once abundant throughout the North Pacific. Identifying a Sirenian Sirenians are large, slow-moving, aquatic mammals that live in shallow marine and freshwater habitats in tropical and subtropical regions. Their preferred habitats include swamps, estuaries, marine wetlands, and coastal waters. Sirenians are well-adapted for an aquatic lifestyle, with an elongated, torpedo-shaped body, two paddle-like front flippers, and a broad, flat tail. In manatees, the tail is spoon-shaped and in the dugong, the tail is V-shaped. Sirenians have, over the course of their evolution, all but lost their hind limbs. Their hind limbs are vestigial and are tiny bones embedded in their body wall. Their skin is gray-brown. Adult sirenians grow to lengths of between 2.8 and 3.5 meters and weights of between 400 and 1,500 kg. All sirenians are herbivores. Their diet varies from species to species but includes a variety of aquatic vegetation such as seagrass, algae, mangrove leaves, and palm fruit that falls into the water. Manatees have evolved a unique tooth arrangement due to their diet (which involves the grinding of a lot of coarse vegetation). They only have molars that are replaced continuously. New teeth grown in at the back of the jaw and older teeth move forward until they reach the front of the jaw where they fall out. Dugongs have a slightly different arrangement of teeth in the jaw but like manatees, teeth are continuously replaced throughout their life. Male dugongs develop tusks when they reach maturity. The first sirenians evolved about 50 million years ago, during the Middle Eocene Epoch. Ancient sirenians are thought to have originated in the New World. As many as 50 species of fossil sirenians have been identified. The closest living relative to sirenians are the elephants. The primary predators of sirenians are humans. Hunting has played a major role in the decline of many populations (and in the extinction of the Stellars sea cow). But human activity such as fishing, and habitat destruction can also indirectly threaten sirenian populations. Other predators of sirenians include crocodiles, tiger sharks, killer whales, and jaguars. Key Characteristics The key characteristics of sirenians include: large aquatic herbivoresstreamlined body, no dorsal fintwo front flippers and no hind legsflat, paddle-shaped tailcontinuous tooth growth and replacement of molars Classification Sirenians are classified within the following taxonomic hierarchy: Animals Chordates Vertebrates Tetrapods Amniotes Mammals Sirenians Sirenians are divided into the following taxonomic groups: Dugongs (Dugongidae) - There is one species of dugong alive today. The dugong (Dugong dugong) inhabits coastal marine waters of the western Pacific and Indian Oceans. The dugong has a V-shaped (fluked) tail and males grow tusks.Manatees (Trichechidae) - There are three species of manatees alive today. Members of this group are usually solitary animals (except for mothers with their young). Manatees prefer freshwater aquatic habitats and coastal saltwater marshes. Their distribution includes the Caribbean Sea, the Gulf of Mexico, the Amazon Basin, and parts of West Africa such as the Senegal River, Kwanza River, and Niger River.

Dancing Ghost Halloween Science Magic Trick

Dancing Ghost Halloween Science Magic Trick This Halloween, make a paper ghost dance in the air, as if by magic! This is a simple and educational holiday science project. Dancing Ghost Materials Light-weight paper works best for this project, such as tissue paper, paper towels, toilet paper or printer paper. paperscissorsballoon Make the Ghost Dance! Cut a ghost shape out of the paper. If you cant cut out a ghost or draw one freehand, search Google images for paper ghost cut-out and print a pattern.Blow up the balloon and tie it off.Rub the balloon on dry hair.Slowly edge the balloon toward the paper ghost. You can make the ghost move in response to the balloon and even make it dance in the air. How It Works When you rub a balloon on your hair, some of the electrons from your hair move over to the balloon, producing a charge of static electricity. The electrons have a negative charge. They are attracted to objects that have a positive electrical charge, like paper. Even though static electricity is invisible, it is powerful enough to draw the paper toward it. When the paper and balloon come into contact, the charge is neutralized and the paper falls back down. More Projects More Halloween Science ProjectsScience Halloween Jack-o-LanternsBend Water With Static ElectricityWater Into Blood Science Trick