The Big Picture Finding the Main Idea and Supporting Details in Expository Text.

What is.... Main Idea: the concept or thought that is most important in the passage. Supporting Details: offer proof or explanation of the main idea. Specific statements that support the main idea.

Think of Main Idea and Supporting Details as..... a table. The table top is the main idea of the passage or paragraph. The legs of the table are the supporting details. Without these details or legs, the main idea or table top would collapse.

Things to remember when finding the main idea. There are four different types of paragraph structures in which main idea can be located. Let’s examine each type.

Structure #1 Usually the main idea is directly stated as the first sentence of a paragraph. The rest of the paragraph provides the supporting details. Clara Barton, known as America’s first nurse, was a brave and devoted humanitarian. While caring for others, she was shot at, got frostbitten fingers, had severe laryngitis twice, burned her hands, and almost lost her eyesight. Yet she continued to care for the sick and injured until she died at the age of 91.

Structure # 2 Once in a while the main idea may appear in the center of the paragraph, surrounded on both sides by details: The coral have created a reef where more than 200 kinds of birds and about 1,500 types of fish live. In fact, Australia’s Great Barrier Reef provides a home for a great variety of interesting animals. These include sea turtles, giant clams, crabs, and crown-of-thorns starfish.

Structure # 3 Often the main idea comes at the end of the paragraph as a summary of the details that came before: Each year Antarctica spends six months in darkness, from mid March to mid September. The continent is covered year-round by ice, which causes sunlight to reflect off its surface. It never really warms up. The coldest temperature ever recorded on Earth was in Antarctica. Antarctica has one of the harshest environments in the world.

Structure # 4 Sometimes the main idea is not directly stated and must be inferred from the details given in the paragraph. This paragraph structure is the most challenging: The biggest sea horse ever found was over a foot long. Large sea horses live along the coasts of New Zealand, Australia, and California. Smaller sea horses live off the coast of Florida, in the Caribbean Sea, and in the Gulf of Mexico. The smallest adult sea horse ever found was only one half-inch long! In this example, the implied main idea is that sea horses’ sizes vary based on where they live. When the main idea isn’t stated, you have to pull together the details to find the key idea. A good way to do this is to think about the “reporter questions”: who, what, when, where, why, and how. The passage may present the answers in any order however, not all of the questions can always be answered.

A trick to finding main idea on multiple choice tests: Read the entire passage. Evaluate the answer choices. Reread each sentence and put a tally mark to each answer choice that relates to that sentence. Add the tally marks. Double check your answer choice. Ask yourself... Does that make sense? Is that the big picture?

Let’s put the READ strategy to work: People have damaged the Amazon rain forest. They have removed soil in search of precious metals. The dirt left behind is not suitable for growing anything. Millions of trees get cut down every year for furniture. With fewer trees, more soil washes away. Dams built to stop floods and make electrical power have backed up rivers. Blocking a river creates a lake that leaves everything underwater for miles behind the dam. All of these actions have left the world’s largest rain forest in danger. The main idea is: a) The world’s largest rain forest is the Amazon River Basin. b) Dams leave everything behind them underwater for miles. c) In the Amazon rain forest, trees are being cut down. d) People have done things that have hurt the Amazon rain forest.

Now try the READ strategy on your own: When oxygen comes in contact with most metals, they rust. Aluminum does not rust. It reacts with oxygen in a different way. It forms a tough surface film that stops rust. This is why people use aluminum to make cars and airplanes. It’s also used as a building material. Your home may have aluminum siding. However, aluminum does not have the strength of steel. When weight must be supported, even rusty steel works better than aluminum. What is the main idea? a) When weight must be supported, even rusty steel is better than aluminum. b) Your home may have aluminum siding. c) Aluminum does not rust. d) Aluminum is often used to make cars and airplanes.

Closure: In your groups discuss the differences between supporting details and main idea.