Changes to the Environment by Humans and Natural Causes

What kinds of things do humans do that are NEGATIVE for the environment?

• planting new trees when older ones are cut down

• reducing emissions from cars and factories

• allowing herding animals to overgraze land

• recycling metal, paper, and plastic products

Which is the best example of an organism having a long-term impact on an environment?

• beavers building a dam

• bears hibernating for the winter

• seasonal migration of birds

• lions hunting other animals

What effect would a beaver building a dam have on the environment?

• creation of a pond

• creation of a forest

• creation of a tundra

• creation of a grassland

Large parts of a forest are cut down to build factories near a city. What would be the most likely effect of cutting down the forest?

• an increase in the amount of rainfall

• an increase in the number of forest fires

• a decrease in the temperature of the region

• a decrease in the habitat of plants and animals

A volcano erupts, spreading ash and rock all over the surrounding forest. The eruption destroys most of the plants and animals in the forest.

What is a possible benefit of the volcanic eruption?

• Destruction of the forest will allow humans to live on the land.

• The volcanic eruption will remove unwanted plants and animals.

• The soil will be fertilized by the ash, allowing new plants to grow.

• More land will be available for large animals to graze.

Sara read that beavers make small dams of tree branches and twigs across streams.

How can such a dam have a negative effect on the environment?

• It creates a shelter for new plants.

• It creates a shelter for new animals.

• It washes away the nutrients from tree roots.

• It blocks the supply of water to animals downstream.

An oil tanker traveling across the ocean accidentally spills a huge amount of oil in the water. What will be one major effect of the oil spill?

• a shortage of drinking water

• a loss of plant and animal lives

• a decrease in the amount of rainfall

• an increase in the temperature of the region

A drought is a long period of time with no rain. What will probably happen to the plants and animals in an area during a drought?

• Most will learn to live without water.

• They will all hibernate until the rain comes.

• They will all die and nothing will ever live there again.

• Some will die, some will live, and some will move to a new place.

How can a forest fire be helpful to plants?

• After a forest fire clears space, plants can receive more sunlight.

• Ash from a forest fire adds minerals to the soil, which helps plants grow.

• Space cleared by a forest fire can become habitat for

  animals that live in meadows.

• All of the above.

A 300-year-old tree is struck by lightning. It falls to the forest floor. What changes will this event cause in the tree's ecosystem?

• Plants that grow best in shade will grow bigger.

• Plants that grow best in sunlight will die.

• Birds that nested in the tree will have to nest in another tree.

• It will cause no changes in the tree's ecosystem.