The Biosphere for Middle School Science

Feb 25

4 min read

The biosphere is the part of Earth where all living things exist. It includes land, water, and even the air, where organisms can survive. From the deepest oceans to the highest mountains, the biosphere supports millions of different species, including plants, animals, fungi, and microscopic organisms. It interacts with the atmosphere (air), hydrosphere (water), and geosphere (land) to create the perfect conditions for life.

If you would like to get the unit on the biosphere, including the picture book and flashcards, you can find it at Teachers Pay Teachers.

The Biosphere

The biosphere is the part of the Earth that supports life. Most of the life on Earth lives between about six kilometers above sea level and 500 meters below the surface of the ocean. However, the entire biosphere extends twenty kilometers from top to bottom. Ruppel's vulture flies 11,300 meters high in the atmosphere, and life has been found in the bottom of the Marianas Trench ten kilometers under the surface of the ocean.

The biosphere is made up of both biotic and abiotic factors. Biotic factors are anything that is living or once was living. For example, grass is a biotic factor because it is alive. Abiotic factors have never been alive. Water is an abiotic factor.

Other spheres on Earth are a part of the biosphere. The lithosphere contains all of the solid rock on Earth. Some of the lithosphere is in the biosphere, but some of it is too deep to support life. The atmosphere is made up of the air that surrounds Earth. Part of the atmosphere is in the biosphere, but it also extends up 480 kilometers above the surface of the Earth. Finally, the hydrosphere is all of the water on Earth, including water in the atmosphere and underground water. Again, some of the hydrosphere is in the biosphere, but the world's biggest ocean was recently discovered deep underground in the mantle. The mantle is one of the Earth's inner layers.

Ecologists study the biosphere, but it is too big to explore all at once. Instead, ecologists focus on different levels of organization. The smallest level is an organism. An organism is one individual from a species. For example, an ecologist could study one blackberry plant or one squirrel. The next level is population. A population is a single species that lives in the same location. A population would include all of the salmon off the coast of Alaska. The next highest level is a biological community. It consists of all of the populations living in the same location. Biological communities only include biotic factors. An ecosystem is the next highest level of organization. It consists of all of the biotic and abiotic factors in the same location. Biomes, the next level, include all of the ecosystems with similar climates. The ecosystems of a biome are spread all over the Earth. The highest level of organization is the biosphere. It includes all the places on Earth that support life.

So far, the Earth is the only planet we know of with a biosphere. We haven't found life on any other planets in our solar system or beyond. We don't know why or how life started on Earth, but its distance from the Sun makes the temperature just right for life. For example, Earth has liquid water on its surface, and scientists believe liquid water is essential for life.

The biosphere has existed for over 3.5 billion years, almost as long as the Earth has existed. The first life on Earth was prokaryotes. Prokaryotes are very simple creatures. They are made up of one cell and don't have any specialized organelles. Bacteria is a type of prokaryote.

Around two billion years ago, early life on Earth changed the biosphere. Cyanobacteria, a type of prokaryote, began combining the energy from sunlight, carbon dioxide, and water to form sugar and oxygen. Scientists call this process photosynthesis. Cyanobacteria produced so much oxygen that they changed Earth's atmosphere. Organisms that can use oxygen to make energy are far more efficient than those who don't. As a result, more complex life began to appear on Earth.

Changes in the lithosphere also affect the biosphere. The lithosphere is made up of giant, solid rock plates that float on the hot liquid rock of the mantle. When these rocks crash into each other, they form mountains and volcanoes that create new ecosystems on Earth. When wind or water scrapes away rock, it changes the biosphere too. Scientists call these changes weathering and erosion.

Today, humans are affecting the biosphere too. When we burn fossil fuels, we are adding carbon dioxide to the atmosphere and hydrosphere. Without human interference, the biosphere is a self-regulating and self-sustaining system. The rock cycle, water cycle, carbon cycle, nitrogen cycle, and other cycles move abiotic factors around the environment to keep the system balanced. As humans have found through trying to create artificial biospheres, our biosphere is a complex system that can't be easily replicated.

Here are some biosphere digital flashcards to help you review.