The Biosphere: Life on Earth

Biosphere

Earth’s biosphere is the layer of the planet where life exists.

That means you, me, all plants, insects, bacteria and living things on land, air and oceans make up the biosphere.

And in case you were wondering… viruses are part of the biosphere too. But they can be a bit tricky.

Today, let’s explore Earth’s biosphere. One of Earth’s spheres that is completely unique to our planet.

What are examples of the biosphere?

Food Chain

Organisms in the biosphere rely on each other as part of the food chain. The food chain is the building block of the biosphere where energy is transferred from one level to the next.

Plant life and ocean phytoplankton (tiny plant-like organisms in the oceans) are examples of primary producers. These organisms are at the bottom of the food chain and power the entire biosphere.

Herbivores feed on plants. Then, predators consume herbivores. Humans and apex predators are considered to be at the top of the food chain.

Finally, decomposers break down matter so they can be recycled as part of the nutrient cycle. This completes the full circle because all matter becomes part of the food chain once again.

What diagram illustrates the biosphere?

Biosphere Diagram

The biosphere is all closely tied together as a collection of different parts. The biosphere (living organisms) interacts with the hydrosphere (liquid water), lithosphere (solid rocks), cryosphere (frozen ice) and atmosphere (gas envelope).

For example, living things inhale oxygen and exhale carbon dioxide (CO2) from the atmosphere. Then, plants pull CO2 during photosynthesis to build their structure (mostly glucose).

The biosphere constantly interacts with Earth’s spheres. For example, living things pull water from the soil and air. And oceans soak up carbon from the air. Finally, specific bacteria from the biosphere are only capable of building certain types of rocks.

Where is the biosphere on Earth?

You can find life anywhere on Earth. Where there’s life, the biosphere is present. Even in the most extreme circumstances, life can persist. For example, polar regions, ocean vents and the deep biosphere are extreme environments in their own unique way. But they can all harbor life.

Polar Regions

Broken Ice Glacier Snow Cold Landscape
Plants and animals in polar climates endure frigid temperatures year-round. For example, Antarctica is the world’s largest desert averaging −10°C to −60°C. In these polar regions, the biosphere mostly consist of algae, lichens and mosses. Animals exist too. For example, penguins eat krill, a fish common in the Southern Ocean. They also have a thick layer of skin and feathers (for waterproofing) for surviving the frigid temperature.

Hydrothermal vents

Hydrothermal Vent
Deep beneath the ocean, the Earth cracks open. Iron-rich sulfur, carbon dioxide and minerals spew out at these underwater volcanoes. But what’s surprising is how hundreds of species of animals can still flourish. They don’t need light to survive. Instead, they rely on a process called chemosynthesis [1]. Even more interesting is that these underwater vents are possibly the origin of the Last Universal Common Ancestor (LUCA).

Deep biosphere

Asthenosphere
The deep biosphere extends deep into the Earth’s crust. Similar to hydrothermal vents, microorganisms can thrive. For example, bacteria were found in the crevices of rocks at 500 meters depth [2]. As deep as 3 kilometers, bacteria exist in anaerobic, hot and high-pressure environments. 90% of Earth’s carbon resides inside Earth [3] which is the chemical backbone for all essential organic molecules produced by living organisms.

How old is the biosphere?

The biosphere is unique to Earth because it’s the only planet known to support life. It’s believed that Earth’s biosphere started about 3.5 to 4.1 billion years ago. All living things originated from a common ancestor called the last universal common ancestor (LUCA).

Archaea are believed to be the oldest domains of life. They make up a group of the first organisms to appear on Earth. We know this because they are used to extreme environments like those during the early Earth. Archaea resembles both eukarya and bacteria. They are single-cell without a nucleus. But they look like bacteria for structure.

Since the evolution of our very early ancestors, the biosphere has altered land, air and water over billion years.

LUCA Timeline

How much does the biosphere change?

Earth Metabolism

The biosphere is constantly in flux. It fluctuates in the short-term based on the seasons. And it changes in the long-term from climate change.

Net primary productivity is unique to the biosphere. It’s the rate at which plants take in carbon dioxide during photosynthesis minus respiration.

Productivity peaks in the summer for mid-latitude regions. But when winter comes, productivity drops because the lower rate of photosynthesis.

Tropical rainforests are the most productive places on the planet. Whereas, polar regions are the least productive ecosystems.

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References

The Depths Below – Life on a Vent. National Oceanic and Atmospheric Administration (NOAA)
Crucial crises in biology: life in the deep biosphere. Int Microbiol. 1998 Dec;1(4):285-94.
The Deep Carbon Observatory. Decade of Discovery Catalyst for the Future.

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