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Transcript
TWENTY FIRST CENTURY SCIENCE KEY STAGE 3 TO KEY STAGE 4 Classification of mammals Mammals are vertebrates which share a set of common characteristics. The list below describes properties that mammals have in common, but there are exceptions. Mammals are covered in hair or fur They are warm blooded They give birth to live young Females produce milk to suckle their young when they are born Most mammals live on land They have four limbs In the boxes below are descriptions of some common mammals. Lion Carnivore Fur covered Warm blooded Live on land Gives birth to live young Mother suckles infants Powerful limbs, sharp claws Elephant Herbivore Body covered in fine sparse hair Warm blooded Lives on land Gives birth to live young Mother suckles infants Sturdy limbs with sponge-like feet Beaver Herbivore Fur covered Warm blooded Lives mainly in water but also on land Gives birth to live young. Mother suckles infants Short front paws with large claws, and larger back legs with webbed feet Dolphin Carnivore Body covered in thick tough skin Warm blooded Lives entirely in water Gives birth to live young Mother suckles infants Two short front flippers, and a dorsal fin on its back To do Draw a table in your book with the following headings. Use the descriptions of the four mammals to complete the table with the correct characteristics: Characteristics that mammals share with other vertebrate groups Characteristics that most mammals have, but which no other vertebrate group have Characteristics that all mammals have, but which no other vertebrate group have Do you think four animals is a large enough sample to study to come up a definite set of characteristics? Case study by Helen O’Connor from Preston Manor High School, Wembley © in this format University of York and Nuffield Foundation 2008 • downloaded from www.21stcenturyscience.org What characteristics do dolphins have which mean they are characterized as mammals and not fish? What kind of animal is the duck-billed platypus? To study The duck-billed platypus was first described in 1797. This account described a small fur-covered animal with webbed feet and a beaver-like tail. The head has a flat beak like a duck. The body shape is similar to a crocodile, with short legs spread out to the sides. It lives in both water and land. It has webbed feet for efficient swimming; long sharp claws on the feet help it burrow out a den. The duck-billed platypus lays soft-shelled eggs like those of a lizard. But when the young hatch out of their eggs, the platypus babies drink milk produced by their mothers. When scientists first read about this strange new animal, they didn’t believe it. Sailors often returned from abroad with wild stories about dragons and other monsters. However, when a respected biologist dissected a pair of duck-billed platypus specimens, preserved by pickling, the scientific world was stunned to learn that it was a genuine animal. Scientists had difficulty believing there was an animal that could lay eggs and also suckle its youngsters. The duck-billed platypus is from Australia, which had become isolated from the other continents millions of years ago after the super-continent Pangaea broke up. Because of this, Australia preserved many animals which no longer exist anywhere else in the world, including the duck-billed platypus and the marsupials such as kangaroos and opossums. The platypus is now protected now by law in Australia. For pictures of a duck-billed platypus, type ‘duck-billed platypus’ into the Images area of a search engine. To do and to answer 1 Read the information above in your groups. Write down any questions you want to ask, and be ready to share this with the class. This can be about information you don’t understand, or something you want to find out more about. 2 Read the information again, this time selecting the key scientific information (by underlining or highlighting) that will help you decide which vertebrate group the duck billed platypus belongs to. 3 Create a table with headings: characteristics of mammals • characteristics of reptiles • characteristics of birds Copy the information you have highlighted into the correct column. Case study by Helen O’Connor from Preston Manor High School, Wembley © in this format University of York and Nuffield Foundation 2008 • downloaded from www.21stcenturyscience.org 4 Decide, with reasons, which vertebrate group the duck-billed platypus belongs to. Duck-billed platypus: Extension activity To study Scientists publish new findings on the duck-billed platypus An organism’s characteristics are determined by genes. Our skin, eye and hair colour, height, weight, sex and blood group are examples of characteristics which are determined by genes. We human beings have about 30,000 genes, but simpler organisms have a lot fewer genes. The more genes that humans have in common, the more similar they are. It follows that the more genes two different animals have in common, the more similar they are. In the last 30 years, scientists have developed a method for finding out exactly what each gene is made of. They call this method ‘gene sequencing’. Because most animals have many thousands of genes, this is not an easy or quick process and often involves teams of scientists working together all over the globe. Quite recently over a hundred scientists working in America, England and Australia managed to work out the gene sequence of the duck-billed platypus. They told the rest of the scientific community about their findings by publishing their results in a Journal called Nature. To work out what the genes a platypus had, the scientists needed to take a small tissue sample from a duck-billed platypus. This came from a female, nicknamed Glennie, which had been captured in the wild in New South Wales, Australia. They compared her genes with small sections from about 100 platypuses living in the wild. They found out that a duck-billed platypus has about 18,500 genes. The duck-billed platypus is classified as a mammal despite the fact that it lays reptile like eggs, and has the bill of a duck and webbed feet. Scientists found that the most of the genes in the platypus were shared with other mammals, but some genes were more like reptile genes and others were like bird genes. To do and to answer 1 Read the information through carefully in your groups. Write down any questions you want to ask, and be ready to share these. The questions can be about information you don’t understand, or something you want to find out more about. 2 Why do you think it was important to have many scientists working to find the gene sequence of the duck billed platypus? Case study by Helen O’Connor from Preston Manor High School, Wembley © in this format University of York and Nuffield Foundation 2008 • downloaded from www.21stcenturyscience.org 3 Why is it important that scientists share their findings with other scientists when they discover something new? 4 Do you think this new discovery of the duck-billed platypus genes means that early scientists were right or wrong to classify it as a mammal? Case study by Helen O’Connor from Preston Manor High School, Wembley © in this format University of York and Nuffield Foundation 2008 • downloaded from www.21stcenturyscience.org