Have you ever thought about where the things you use come from? If the things you use do not come from nature, they are man-made. We use millions of man-made things every day.

To begin with, you have to tell what things are natural. Now take a look at the beautiful river covered with ice. The ice on the river is natural while the ice in the fridge is man-made.

How about glue, pencils and money?

Is glue natural or man-made? Well, glue used to be natural in the past. People just found some materials sticky. Then they were used as glue. In modern times, glue companies put at least four materials together in a new way to produce glue. So glue is changed to be man-made.

Pencils are made mostly from wood, graphite (石墨) and clay that come from nature. The materials are changed by adding other materials and heating to make something new—a pencil!

Think about money! We have paper money made of paper and coins made of metals, so they are natural, right? No. Its production is not an easy task. Creating money requires special machines and printing skills to make the paper or metals into money.

We are living in a world full of man-made things. Is that a good thing or a bad thing? You must decide for yourself.

Different weather makes people feel different. Weather influences health, intelligence（智力）and feelings.

In August, it is very hot and wet in the southern part of the United States. People there have heart trouble and other kinds of health problems during this month. In the Northeast and the Middle West, it is very hot in summer and very cold in winter. People in these states have more heart trouble when the weather changes in February or March.

The weather can also influence intelligence. For example, in a 1983 report by scientists, the IQ of a group of students was very high when a very strong wind came, but after the strong wind, their IQ was 10% lower. The wind can help people have higher intelligence. Very hot weather, on the other hand, can make it lower. Students in many schools in the United States often get worse on exams in the hot months of the year (July and August).

Weather also has a strong influence on people’s feelings. Winter may be a bad time for thin people. They usually feel cold during these months. They might feel unhappy during cold weather, too. But fat people may have a hard time in hot summer. At about 18℃, people become stronger.

Low air pressure（气压） may make people forgetful. People leave more bags on buses and in shops on low-pressure days.

Are you feeling sad, tired, or forgetful today? It may be the weather’s problem.

Plants, animals and people are living things. Living things are alive. Living things can grow and change. When they grow up, living things can have young living things. Many living things can move.

Most living things need air, water and food to live. Most living things need space to grow. Many living things need shelter (庇护处).

Nonliving (无生命的) things were never alive. They don’t grow on their own. They don’t change. They don’t have needs.

Some nonliving things come from nature. Water is a nonliving thing from nature.

Some nonliving things are made by people. People make toys. Some toys look and move like living things. But these toys are nonliving things.

Then what do plants and animals need to live?

Plants need sunlight, water. Plants also need nutrients (营养). Nutrients help plants grow and make food. Plant need places to grow.

Many animals need air to live. And they all need clean water and food. They need shelter, too. A shelter is a safe place to live in.