On Earth, living things that can survive in extreme environments (similar to space) are called _____.

Some scientists think that the conditions that support life on Earth are _____; they think that life probably only exists on Earth.

Some scientists think that the conditions that support life on Earth are _____, they think that life probably exists in other places in the universe.

There are many factors that scientists think makes Earth a(n) _____ planet - meaning having the conditions necessary to support life.

All living things require _____ for their survival; it is used for growth, movement, repair, and reproduction.

Earth formed around a yellow _____ star (our Sun) that will use it's fuel slowly and be a source of energy for billions of years.

All living things require nourishment (also called _____) for their survival.

On Earth, plants are _____ and can transform energy from the Sun (sunlight) into food molecules.

Plants use the process of _____ to produce their own food from sunlight.

Earth has enough _____, the "organic" substance that all life on Earth is based on, to cycle between living things.

On Earth, all _____ (the smallest unit of life) and all food molecules are "built" using carbon.

Earth has a(n) _____, a layer of gases that surrounds our planet.

Earth has a large enough _____ to have enough gravity to hold its atmosphere in place.

Smaller planets with less gravity (like Mercury and _____) have lost their atmospheres over time as gases have drifted off into space.

Most all living things require _____ gas (found in the air) for their survival.

Earth's atmosphere contains the right mixture of _____ - importantly it has enough oxygen to support life.

We say that Earth's atmosphere is _____; because it contains enough oxygen to support life.

Our Sun gives off _____light, which is a form of low-energy radiation that is harmful to living things.

Earth's atmosphere has a thin _____ layer that helps shield Earth from most of the harmful ultraviolet (UV) radiation from the Sun.

Most living things require a stable _____ that does not change by large amounts.

Earth's atmosphere also contains _____ gases (like carbon dioxide), which are gases that temporarily trap heat energy from the Sun.

Greenhouse gases cause the "greenhouse effect," which (similar to a greenhouse for plants) has an overall _____ effect on Earth.

Venus, the hottest planet in our solar system, has a thick atmosphere which causes a _____ greenhouse effect.

All living things require liquid _____ for their survival.

Earth is the right distance from the Sun; scientists say it is in the "_____ zone."

The habitable zone is sometimes called the _____ Zone; because, like in the children's story, the temperature is "just right" - not too hot & not too cold.

In part, because it is the right distance from the Sun, Earth has plenty of _____ water at its surface.

Liquid water is important because it can _____ lots of substances, which helps living things move nutrients into the cells that make-up their bodies.

Earth has enough internal _____ to keep some of the materials deep under its surface melted.

The motion of the melted metals deep inside the Earth (along with Earth's rotation) creates Earth's _____ field.

A(n) _____ is one way that we can observe Earth's magnetic field.

_____ radiation is a deadly form of high-energy radiation from deep space that is very dangerous to living things.

Earth's magnetic field acts like a _____ that protects Earth from dangerous solar and cosmic radiation.

NASA's _____ Space Telescope was built to look for planets orbiting other stars in other solar systems.

Any planet that orbits a star in another solar system is called a(n) _____.

Some scientists suspect that some of the Jovian _____ in our own solar system have the conditions that support life.