Bony Or Boneless

Bony or Boneless?

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HOW LONG?!

• We can tell from fossils that living things have been on Earth for over three billion (3,000,000,000) years. Those living things were not like you and me. They were very small and made of only one cell. A cell is the smallest part of any living thing, and a human being has trillions of cells, so you can see how small those living things were. Even though they were tiny, they were alive.

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Our Ancestors

• Those tiny things were the ancestors of all living things today. We say that all life has evolved from them. Evolution is a word meaning change in living things over long periods of time, producing new kinds of living things.

A Sponge? Are you serious? 700 million (700,000,000) years ago, the first animal did not look like a dog or a cat. It was a sponge, a thing without a brain or nerves or a backbone. Q u ic k T im e ª a n d a d e c o m p re sso r a r e n e e d e d t o s e e t h is p ic t u r e .

It sat on the bottom of the ocean and ate bits of food in the water, but it was an animal. Maybe that does not sound like an animal to you, but it does to a zoologist.

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To a scientist, an animal is a living thing, made of many cells, that can move (at least part of its life) and must eat other living things. Animals are one of the five kingdoms of living things.

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Close your eyes. Think of a dog.

• Did you think of a retriever, a chihuahua, a golden retriever, or a beagle? All of these are dogs. They are very closely related, even though they look different. All dogs are the same species. • A species is a group of living things that is closely related and can have young together.

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Organizing animals into groups is called classification, and it is an important science skill. Scientists classify living things according to how they are related, using many different clues. If they see that kangaroos and elephants both have hair and feed milk to their young, they group both kangaroos and elephants as mammals.

Animals are classified into TWO large main groups. • 98 out of 100 types of animals in the world today are INVERTEBRATES, like a sponge, because they do not have backbones. • Animals with backbones are called VERTEBRATES, and they have only been around for about 500 million years.

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Invertebrate s like insects are the most common type of animal on Earth

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Why are people so interested in vertebrates, when there are so few of them? Vertebrate animals are a big part of human life. Humans have dogs and cats as pets, they ride horses, they feed squirrels, and they raise cows for meat. And, vertebrates can be much bigger than invertebrates, so they are easier to see.

Any other reasons? Oh yeah, human beings are vertebrates, related to all the other vertebrates. If you feel your back, you can feel QuickTimeª and a decompressor the bones running down are needed to see this picture. the center. That is your backbone. The history of vertebrate animals is the history of you and me.

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• Vertebrates are divided into five main classes: fish, amphibians, reptiles, birds, and mammals. All of these are animals because they move around, are made of many cells, and eat other living or once-living things. They ALL have backbones.

Teacher Websites:

• http://www.dmturner.org/Teacher/Libra • http://std2groupinganimals.blogspot.co

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Task

• Your teacher will now pass out a sheet with pictures of animals, all jumbled up. Your task is to separate out the vertebrates from the invertebrates and present your findings on a poster.