Sea otters spend nearly their whole lives in the cold kelp forests along the Pacific coast, where they find both food and shelter. Scientists study the otter's habitat there. What does habitat mean in this text?

In the Florida Everglades, a great blue heron stands still until a fish swims close, then stabs it with its beak. Biologists call the heron a predator of small fish. What does predator mean here?

Each fall, monarch butterflies leave the northern United States and fly up to 3,000 miles to fir forests in central Mexico. Scientists tag the butterflies to study how they migrate. What does migrate mean here?

Earth takes about 365 days to go all the way around the Sun and return to where it began. The Moon takes about 27 days to orbit Earth in the same way. What does orbit mean here?

For millions of years the Colorado River has cut into rock in Arizona, carrying tiny bits of stone downstream. The canyon it left is over a mile deep. Geologists study this erosion. What does erosion mean here?

Quartz and halite are solid materials that form in the ground on their own, without any help from plants or animals. Each has its own hardness and shape. Both are a mineral. What does mineral mean here?

A woodchuck eats heavily all fall, then stays in its burrow from October until March. Its heartbeat slows down and it takes no food at all while it hibernates. What does hibernate mean here?

The snowshoe hare's brown summer fur turns white before winter, so it is hard to spot against the snow. Foxes often pass right by it. Its camouflage keeps it safe. What does camouflage mean in this text?

The last known passenger pigeon died at the Cincinnati Zoo in 1914, and no one has seen one alive since. Scientists say the passenger pigeon is extinct. What does extinct mean here?

Diggers in Montana pulled bones of a Tyrannosaurus rex from the rock. Over millions of years, the buried bones had slowly turned to stone. Museums put the fossil on display. What does fossil mean here?

In 1607, about one hundred English men and boys sailed to Virginia and built the town of Jamestown, clearing land and planting crops. Each settler hoped for a new life. What does settler mean here?

In 1783, leaders from Britain and the United States met in Paris and signed the treaty that ended the Revolutionary War. In it, Britain agreed the United States was free. What does treaty mean here?

Before 1776, thirteen places along the Atlantic coast, such as Virginia and Georgia, were ruled by Britain and had to obey British laws. Each one was a colony. What does colony mean here?

The United States declared independence in 1776. A century later, in 1876, Americans filled a huge fair in Philadelphia to celebrate the birthday. What does century mean here?

Alexander Graham Bell built a machine that carried a human voice along a wire, and in 1876 the patent office gave him the rights to it. The telephone was his invention. What does invention mean here?

Florida stretches south into the ocean with water on its east, south, and west sides, and it joins the rest of the country only along its northern edge. Florida is a peninsula. What does peninsula mean here?

Yuma, Arizona gets less than four inches of rain in a whole year, and its summer days often climb past 100 degrees. Its dry climate is nothing like Seattle's. What does climate mean here?

In Alaska, a huge sheet of ice packed down from centuries of snow creeps down a valley, scraping the rock beneath it. A glacier may move only inches in a day. What does glacier mean here?

Boston's shoreline curves inward, so ships can rest in calm water there, out of the reach of ocean waves and wind. Boats have unloaded in that harbor for hundreds of years. What does harbor mean here?

As the Mississippi River nears the Gulf, it slows down and drops the mud it has carried, spreading fan-shaped new land across southern Louisiana. Maps show the river's delta there. What does delta mean here?