Previously. From page 20 There are millions of species of living things but we don t really know how many.

Transcription

1 Previously From page 20 There are millions of of living things but we don t really know how many. From page 28 Variation comes about due to genetic and environmental reasons. Unit 5 Remarkable nature How amazing is nature? This Unit is our Guinness Book of Records for nature. We will learn about a small selection of some of the most remarkable animals and plants on Earth. In this Unit, you will learn: qqthat blue whales and giant redwood trees are the biggest living things on Earth; qqhow whales live, feed and communicate; qqwhy bees are important to us and the Earth; q q how honeybees communicate information about food to each other; qqwhy some animals are threatened by human activity; qqthat parrots are amongst the most intelligent of all birds and can solve problems; qqthat a bristle cone pine tree is one of the oldest things on the planet; qqthat Welwitschia is weird! Key words baleen biomass communicate conservation status extinct girth imitate intelligence krill waggle dance Welwitschia 32

2 Remarkable nature What is special about whales? There are 86 of whales, including dolphins and porpoises. Many of them are very rare and one, the Baiji or Chinese River Dolphin, was declared extinct (none left alive) in Here, we will learn about the very large ocean-living whales. We will look in particular at the blue whale, Balaenoptera musculus, which at about 30 metres long and weighing in at kg is the biggest known animal to ever have existed. What does a blue whale eat? Possibly the most remarkable thing about this gigantic animal is that its food is tiny! It feeds almost entirely on krill, a small crustacean that exists in vast numbers. Let s work out just how much krill food whales could find. If we add the mass of all the humans on the planet together, we call the total the biomass of the human. In 2012, there were about humans on Earth. On average, a human has a mass of about 50 kg. Name Blue whale Genus and Balaenoptera musculus Mass kg Length 30 m Food Krill, tiny crustaceans Special skills Communicates by song across hundreds of miles Record Biggest animal we know of, ever So the biomass of humans = kg = 350 billion kg One Antarctic krill has a mass of about 0.5 g, so a human has a mass times bigger than a krill! We think there are about 800 trillion krill living in the Southern Ocean. So what is the biomass of krill? Biomass of krill = g = 400 billion kg So the tiny Antarctic krill living in the Southern Ocean has a total biomass more than that of all humans on the planet! That s a lot of food for whales. However, a blue whale eats around 40 million krill every day. The whale moves forward into a group of krill, and takes them into its massive mouth, together with hundreds of gallons of seawater. The water is squeezed through hard baleen plates that hang from the roof of its mouth. Krill cannot pass through the baleen plates and are swallowed. How much mass of krill does a blue whale eat every day? BIOLOGY 33

3 Unit 5 How do whales communicate? Another remarkable feature of some whales is their ability to communicate with each other in complex ways. Unfortunately, one thing that cannot be done in a book is to convey sounds. The most complex song is that of the male humpback whale. Each song can last for up to 20 minutes, and the males will sing all day. We have not yet worked out why they sing these songs or what they mean. They may be challenges to other males. At certain times of the year, the song changes and is used to herd the fish that these whales eat. Search online for recordings of whale songs. Try using your descriptive writing ability to convey the songs in words to others. Let them read what you have written, listen to the song and ask them what they think of your description. Why are whales under threat? There is much else to learn about whales, but perhaps the most important fact to end with is that humans threaten many of them. So that we can understand which animals are most in danger, the International Union for the Conservation of Nature (IUCN) was formed in The IUCN is working to give all of living things a conservation status. Because of hunting and other human activities, many of whale are threatened. Extinct (EX) Extinct in the Wild (EX) Threatened categories Critically Endangered (CR) Endangered (EN) Vulnerable (VU) Near Threatened (NT) Least Concern (LC) Species World population Conservation status Blue whale under EN Endangered Fin whale under EN Endangered North Atlantic right whale under 300 EN Endangered Sperm whale under 2 million VU Vulnerable Common minke whale not known NT Near Threatened + Extinction risk The categories the IUCN uses to describe how much at risk a can be. 34

4 Remarkable nature What is special about bees? Bees are a huge group of insects (about ) closely related to ants and wasps. Here we are going to look at the Western honeybee, Apis mellifera, and in particular its ability to communicate. How do honeybees live? Honeybees live in colonies of up to individuals. They feed on nectar and pollen collected from local flowers. When a foraging worker finds a new patch of flowers it can communicate information about it to others. The returning bee performs a round dance, telling others that food is within 50 m. It then does a waggle dance, which provides more detailed information about the distance and direction of the food. Sun flower Name Western Honeybee Genus and Apis mellifera Mass 0.25 g (a colony of bees would weigh about 12 kg) Length Just over 1 cm Food Nectar and pollen Special Lives in big colonies skills Communicates by dances Record Helps flowering plants and many crops reproduce through pollination a 2 start 1 1 s = 1 km qqthe angle a of its dance to the vertical shows the direction of the flower relative to the Sun. qqthe length of time it takes to dance the wiggly line, in seconds, measures the distance to the flower in kilometres. qqit returns to the start from the right, repeats the waggle, then returns from the left, and so on. Bees are not the only animals that use unusual methods of communicating with each other. Find out more about bee dances and, in a table, compare this method of communication with that of three other animals and humans. Can you find out any information about communication in plants? BIOLOGY 35

5 Unit 5 Why are bees under threat? Honeybees are very important to us and the environment. qqthey provide us with honey when we keep them in beehives. qqthey make sure most flowering plants and crops reproduce, because they pollinate the flowers. Unfortunately, a combination of natural and human causes means bee numbers have reduced dramatically. qqover the last hundred years the number of beehives in the UK has declined from over 1 million to only qqthere are several diseases that threaten bees in 2008, 30% of all bees in the UK were lost to such diseases. qqhuman activity means that large areas where bees live and forage have disappeared. These areas include traditional meadows and heather moors. Explain why bees are important to the environment around us. What do you think can be done to help bees? What is special about parrots? It is well known that parrots can imitate human speech, but being able to imitate is not the same as having intelligence. Better evidence comes from experiments showing that parrots can solve puzzles. In addition, some parrots have been shown to use language in a creative way. One, an African grey parrot called N kisi, is said to have a vocabulary of 950 words. Once, when the chimpanzee expert Jane Goodall visited N kisi, the bird said got a chimp because it had seen a photograph of her with chimpanzees. 1 Find out how many words a human child will learn by the age of three. What does that suggest about N kisi s intelligence? 2 Keep a vocabulary log by noting every new word you learn in a week. You may be surprised! Name African Grey Parrot Genus and Psittacus erithacus Mass 0.5 kg Length 0.3 m Food Fruit and nuts Special Can imitate human skills speech Able to solve problems Record Largest number of human words learnt by an animal

6 Remarkable nature What is special about General Sherman and the bristle cone pine? If the blue whale is the biggest animal ever to have lived, the giant redwood is probably the biggest plant. For example, the tree called General Sherman is the biggest alive today. It is 83.8 m (275 feet) high and has a girth (distance around it) of over 30 m (100 feet). It is thought to weigh over kg. It accumulates new wood at a rate equivalent to the wood in a 30-year-old oak tree every year. The General Sherman grows, along with other giant redwood trees, in the Sierra Nevada Mountains of California. Name Bristle Cone Pine Genus and Pinus longaeva Mass kg Length About 15 m Food Sunlight, water, carbon dioxide and minerals Special Nearly 5000 years old skills Record Oldest living tree on Earth Name Giant Redwood Genus and Sequoia gigantea Mass kg Length 83.8 m Food Sunlight, water, carbon dioxide and minerals Special Grows enough wood skills every year to make a whole 30-year-old oak tree Record Biggest plant we know of Not very far away in the White Mountains of California grows a bristle cone pine tree called Methuselah, which is nearly 5000 years old! The General Sherman is not in fact the largest living thing on Earth, nor is Methuselah the oldest. General Sherman is the largest single-stemmed tree and Methuselah is thought to be the oldest non-clonal living thing. Using the clues above, see if you can find out which are truly the largest and oldest living things. Write a paragraph about each of them. BIOLOGY 37

7 Unit 5 Why is Welwitschia truly special? Welwitschia has been given a number of different descriptions; the world s ugliest, weirdest, strangest, most wonderful and most bizarre plant. Welwitschia is the only in its genus, the only genus in its family and the only family in its order. There is no other of living thing even remotely like it! It lives on the coast of Namibia and Angola in South West Africa. This region is a dry desert but water is available in early morning mists. Welwitschia consists of a long taproot, a short trunk and just two leaves. The leaves grow throughout the life of the plant, which can be as long as 2000 years. The leaves curve downwards, so that they collect the mist into water droplets. These droplets run into the soil and to the roots. Growing plants have leaves about 2 m long, but the wind blowing them against the sand wears away the growth. If they weren t constantly worn away like this it is thought each leaf would be well over 100 m long! Name Welwitschia Genus and Welwitschia mirabilis Mass 100 kg Length About 2 m Food Sunlight, water, carbon dioxide and minerals Special Lives in very harsh skills conditions Record Very, very unique You need to remember that: qqthe world is full of amazing living things. qqwhales and bees are threatened by qqblue whales are the biggest animals that human activity. have ever lived. qqparrots are amongst the most intelligent qqwhales feed off some of the smallest of all birds and can solve problems. animals on the Earth. q qqwhales communicate with each other by singing under water. q qqhoney bees communicate information some of the oldest things on the planet. qqwelwitschia is weird! about food to each other through waggle dances. q The biggest giant redwood trees are some of the largest living things on the planet. q Bristle cone pine trees can live to be Next time Unit 15 Each living thing is adapted to the place it lives, its habitat (page 95). Unit 16 There are over 7 billion people on Earth, which puts a big strain on the environment (page 104). 38