Do you know a kind of bird called tawny owl? Where does it come from? It comes from Finland (芬兰). What color is it? It is brown. Are all the tawny owls brown? No. Tawny owls come in two colors: pale gray and brown. And in Finland, it often snowed in winter. Many tawny owls were pale gray. But as the Finnish (芬兰的)winters get warmer, there are more brown ones. Why is that?

    The University of Helsinki team tries to study tawny owls. They find that tawny owls get the color from their parents. The gray owls could get food easily in the snow in the past. But now the winter is warmer. There is little snow so the brown owls can live well, too. The number of the owls is getting bigger.

    The leader of the team, Dr Patrick Karell, said that the birds change their color to meet the weather. We are sure the weather change can do something to the animals.

Look up in the sky. Do you see any clouds? What do they look like? Some clouds are fluffy(绒毛状的) and white, like cotton balls. Others are dark almost black, and make you hold an umbrella. At sunrise and sunset, clouds can look red, purple, or yellow—as if they were colored with crayons. But what are clouds anyway?

    You can't reach out and touch the clouds, but you can make your own in a bottle.

    You need

    * an adult helper

    * a huge, empty glass jar

    * a metal strainer(过滤器)

    * hot water

    * ice

    Do these

    Step1. Have your helper fill the jar with hot water, leave it there for two minutes, then pour out most of the water. Leaving just an inch or two at the bottom of the jar.

    Step2. It's your turn, put the strainer over the mouth of the jar, fill the strainer with ice. Watch the jar.

    What happened?

    A cloud formed in the jar! Some of the hot water at the bottom of the jar turned into hot water vapor(蒸汽). The water vapor rose and met with the cold air coming off the ice. When the water vapor condensed, it formed a cloud. Hot air rises and carries with it lots of water vapor, the higher the air rises, the more it cools down. Soon the cold air can't hold all the water vapor so it starts turning into tiny water drops, and becomes a cloud.

Within a plant

It's quarter past seven. Here's Worker No. 55 in his green uniform. He {#blank#}1{#/blank#}(start) work in the plant. 

He works in Workshop 1001 in the Leaf. There are 20 to 100 {#blank#}2{#/blank#}(work) in each workshop. They collect sunlight and CO₂ {#blank#}3{#/blank#} the day. Now workers from the Root send up water. The water {#blank#}4{#/blank#}(rise) up to the Leaf through the Stem. Then workers in the Leaf {#blank#}5{#/blank#}(mix) water, CO₂ and sunlight. 

What are they going to produce? Most {#blank#}6{#/blank#}(important) (for them), there will be sugar! It's {#blank#}7{#/blank#}(use) for the growth of the plant. Another product will be oxygen, but the plant doesn't need much of it. It {#blank#}8{#/blank#}(mean) a lot to animals and humans, though—they need it {#blank#}9{#/blank#}(breathe)!

The workers work hard. Soon it {#blank#}10{#/blank#}(get) dark. They will take {#blank#}11{#/blank#} rest. 

There are {#blank#}12{#/blank#}(million) of plants on earth. They give {#blank#}13{#/blank#}(much) than food and oxygen. {#blank#}14{#/blank#} plants, the natural world would be very different!

A Fun Plant Experiment to Try at Home

Without water, plants would die. How does water get from roots of a plant to the other parts of the plant? The water travels through" small pipes" to all parts of the plant. And here is a scientific experiment to show it. 

What we need:

* a celery stalk(芹菜茎) with leaves

* a knife

* some red food colour from tomatoes

* a glass of water

How we do it:

1. Put a few drops of the red food colour in the glass of water. 

2. Cut the bottom(底部) of the celery stalk and place the celery in the water. 

3. Leave the celery stalk in the glass of water for a few hours. 

4. Take the celery stalk out of the water and cut it into pieces across the stem. 

What happens:

You can see red food colour in all cross parts from the bottom of the celery stalk right up to the leaves. 

Why it happens:

The water, with the red food colour, has run in the celery stalk through the small pipes in it. The experiment, therefore, shows that the small pipes in the plant allow water to reach all parts of it. The red food colour shows where the water has travelled in the celery stalk. 

① We can find ants everywhere— in the forests and mountains, in the fields, in the countryside and cities, all over the earth. But how much do you know about them?

② Their colour is usually yellow, brown, red or black. These little animals live and work in groups. They always build "houses", find food and raise babies together. The colony (群) of ants can be small or large. The number can be from just a few to millions!

③ Usually, there are three castes (等级) in ant societies. They are queens, the males and the workers. Queen ants are usually the biggest ants in colonies.  ▲  It lays (产) all the eggs, so the queen becomes the most important ant in the colony. A queen ant can live for longer. The males have larger wings and larger bodies than the worker ants. They can help out with the colony housework, but mostly they do not. They can only live for a few weeks. The queens and the workers are the winners by numbers. The workers do all the "housework"— from building and cleaning the "house" to looking for food. Workers usually live for several months. Workers are also good at building homes. They can build their homes in different places. You may find their homes under rocks or in the trees. How amazing!

④ One ant by itself cannot bring any danger to many other larger animals. However, they can beat much bigger animals in large groups. By working together, these brave(勇敢的) ants can protect their colonies against other animals.