Main Idea Practice Test

Read the passage. What is the main idea of the passage?

In some coastal areas, mangrove forests grow where land meets the sea. Mangroves have tangled roots that rise above muddy water. These roots slow waves and help protect shorelines during storms. They also trap sediment, which can reduce erosion.

Mangroves provide homes for many animals. Fish and crabs hide among the roots when they are young. Birds rest and nest in the branches. Because mangroves support sea life, nearby fishing communities often benefit.

However, mangroves sometimes disappear when people clear land for buildings or roads. Pollution can also harm the trees. When mangroves vanish, coasts may become more vulnerable to flooding and stronger wave damage.

Protecting mangroves can include setting aside conservation areas and reducing pollution. Some communities replant mangrove seedlings to restore damaged regions.

The passage explains why mangroves are important and how protecting them helps both people and wildlife.

Read the passage. What is the main point discussed in the passage?

In the desert, water is limited and temperatures change quickly. Yet many plants survive there because of special adaptations. A cactus, for example, stores water in its thick stem. Its waxy surface helps prevent water loss.

Instead of broad leaves, many cacti have spines. Spines reduce water loss and protect the plant from animals. Some desert plants grow deep roots to reach underground water. Others spread shallow roots wide to collect rain fast.

Desert animals also depend on these plants. Birds may nest among spines for safety. Small mammals eat fruit or seeds when available. The whole ecosystem relies on careful use of water.

These adaptations develop over many generations. Plants that handle heat and dryness are more likely to survive and reproduce.

The passage explains how desert plants use adaptations to survive with little water.