Third Planet: Earth

The third planet in our solar system is Earth. It is the only planet known to support life and is the largest of the terrestrial planets. Earth is a dynamic and ever-changing planet with a diverse range of ecosystems and environments.

Key Facts about Earth

• Orbit and Rotation: Earth orbits the Sun at an average distance of about 93 million miles. It takes approximately 365.25 days to complete one orbit. Earth also rotates on its axis, completing one full rotation every 24 hours.
• Atmosphere: Earth's atmosphere is composed mainly of nitrogen (78%) and oxygen (21%), with trace amounts of other gases. The atmosphere plays a crucial role in supporting life and regulating the planet's climate.
• Geography: Earth's surface is about 71% water and 29% land. It has diverse landforms, including mountains, plains, plateaus, and valleys. The oceans and continents are constantly shaped by natural processes such as erosion, weathering, and tectonic activity.
• Biosphere: Earth is home to a wide variety of living organisms, from microscopic bacteria to large mammals. The biosphere encompasses all the ecosystems on the planet, including forests, grasslands, deserts, and aquatic environments.
• Climate: Earth experiences a range of climates, from polar regions with ice caps to tropical regions with lush rainforests. The planet's climate is influenced by factors such as the Sun's energy, ocean currents, and atmospheric circulation patterns.

Study Guide

Here are some key points to focus on when studying Earth as the third planet:

1. Describe Earth's orbit and rotation, including the concept of a year and a day.
2. Explain the composition and importance of Earth's atmosphere for supporting life.
3. Identify and describe major geographic features of Earth, such as continents, oceans, and landforms.
4. Discuss the diversity of life on Earth and the interconnectedness of ecosystems within the biosphere.
5. Explore the factors that contribute to Earth's climate and the impact of human activities on the environment.

By understanding these key facts and concepts about Earth, you'll gain a deeper appreciation for our planet and the complex systems that sustain life.