Grade 4 Science Practice Test: Animal and Plant Structures, Rock Layers and Natural Hazards

Roots take in water and minerals from the soil and anchor the plant so wind and rain do not knock it over. Making food from sunlight is mainly the job of the leaves, and flowers make seeds.

Thorns are an external structure for protection: animals that try to eat the stem get poked, so they often leave the plant alone. Water moves up through the inside of the stem, not through the thorns.

A long, thin beak can reach deep inside a tube-shaped flower, the way a hummingbird's beak does. Cracking nuts needs a short, strong beak, tearing meat needs a hooked beak, and scooping fish needs a wide pouch-like beak.

Large eyes gather more of the little light there is at night, so the owl can spot mice and other prey in the dark. Eyes are for seeing; they do not help with smell or warmth.

The heart is a muscle that pumps blood, which carries oxygen and food to every part of the body. The lungs take in oxygen, the stomach breaks down food and the brain processes information.

Water passes over a fish's gills, which take in oxygen that is dissolved in the water. Fins and the tail help the fish move and steer, and scales protect its body.

The blue color could only reach the petals if water moved up through the stem. In a growing plant, the stem carries water from the roots to the leaves and flowers. Plants make sugar in their leaves using sunlight, not in the stem from colored water.

In layers that have not been disturbed, the lowest layer formed first. Layer Z is at the bottom, so the trilobites lived earlier than the mammal in Layer W, the youngest layer. Having no fossils does not make a layer older.

Moving water carries sand and pebbles that slowly erode rock. Over a very long time, a river can cut down through layer after layer, exposing them in the canyon walls, as the Colorado River did in the Grand Canyon.

Matching layers with the same fossils show that the rock formed as one connected set of layers. Later, water or ice wore away the rock in between, leaving a valley. Rock layers are not the same everywhere; they differ from place to place.

During a tornado, strong winds break windows and throw objects. The safest spot is the lowest level, in an inside room without windows, such as a basement, closet or bathroom. Upper floors, porches and cars give much less protection.

People cannot stop an eruption, but scientists can watch for warning signs, such as the ground swelling and gases escaping. Early warnings give people time to evacuate, which reduces harm. Walls, water and trees cannot hold back an eruption.

A tsunami is a series of huge waves that can rush far inland. Getting to high ground or moving away from the coast keeps people out of the water's path. The sea pulling back from shore is a warning sign, not a reason to walk out.

If lightning strikes, the rod and wire carry the electricity safely into the ground instead of through the walls, where it could start a fire. A lightning rod does not keep storms away or store the electricity.

Earthquakes and volcanoes are not spread evenly. Many line up in long belts, and one large belt circles the Pacific Ocean, often called the Ring of Fire. Maps of these patterns help people know which places need earthquake-safe buildings and warning systems.