How did complex life start on Earth?

By: Ayush Johari 

In the vast expanse of the ancient Earth, where the sky glowed with an orange hue and the oceans shimmered in shades of green, a small and unassuming creature emerged, destined to shape the course of life on our planet. This creature was called Phytoplankton, a name derived from the Greek words “phyto” meaning water, and “plankton” meaning drifter. It was through the evolution of these tiny organisms that complex life as we know it came into being.

Around 200 billion years ago, when the Earth’s atmosphere was vastly different from what it is today, Phytoplankton began their remarkable journey. They possessed a unique ability to harness the power of the sun through a process known as photosynthesis. With their chlorophyll-filled cells, they captured sunlight and converted it into energy, producing oxygen as a byproduct.

These microscopic organisms became the architects of a profound transformation. Their prodigious oxygen production gradually infused the atmosphere with this life-giving gas. As their numbers multiplied, so did the oxygen content in the air. The sky, once a warm orange, slowly transitioned into the brilliant blue we now gaze upon.

But the impact of Phytoplankton extended far beyond the colour of the sky. They held a vital role in the intricate web of life that thrived in the ancient oceans. As primary producers, Phytoplankton formed the foundation of the marine food chain. Zooplankton, tiny animal-like organisms, depended on them for sustenance, devouring these plant-like drifters and continuing the transfer of energy up the chain.

The grandeur of the oceanic world reached its pinnacle with the majestic creatures that inhabited its depths. Whales, the gentle giants of the sea, also relied on Phytoplankton for their survival. These colossal beings feasted upon the abundance of Zooplankton, which in turn, had thrived on the nourishment provided by the primary producers.

Yet, the story of Phytoplankton did not end with their pivotal role in sustaining life. Even in death, they remained indispensable. As these diminutive creatures completed their life cycles, their bodies sank to the ocean floor, becoming part of a process known as marine snow. This organic detritus became a feast for a host of scavengers and decomposers, ensuring that no particle of energy went to waste.

Beyond their ecological significance, Phytoplankton played a profound role in shaping the Earth’s atmosphere. Astonishingly, these minuscule organisms are responsible for producing approximately half of the oxygen present in our atmosphere. Every breath we take owes a debt of gratitude to these humble drifters, quietly toiling beneath the surface of the world’s waters.

However, the delicate balance orchestrated by Phytoplankton is not invincible. In recent years, scientists have raised concerns about the impact of human activities on these vital organisms. Climate change, pollution, and the warming of the oceans pose significant threats to the well-being of Phytoplankton populations. Even a small decline in their numbers could have devastating consequences, resulting in a massive drop in the world’s oxygen levels and triggering a cascade of ecological disruptions.

The story of Phytoplankton serves as a powerful reminder of the interconnectedness of life on Earth. From their modest beginnings, these water drifters became the guardians of our atmosphere and the lifeblood of our oceans. Their importance cannot be overstated, and it falls upon us, the stewards of this planet, to ensure their survival and the preservation of the delicate balance they maintain. As we gaze upon the vastness of the blue sky and the shimmering waters, let us remember the profound debt we owe to these humble yet extraordinary creatures—Phytoplankton.