Chapter 1: Introduction to Symbiosis

Is nature fundamentally about competition or collaboration? This question invites us to explore the concept of symbiosis in Part 35 of the History of Earth.

Living Together: Beyond Competition

The conventional view of evolution often portrays nature as a brutal struggle for survival. This perspective, famously expressed by poet Alfred, Lord Tennyson, does not accurately reflect the reality of many species. Contrary to this competitive narrative, numerous organisms thrive through cooperation and symbiotic relationships.

Symbiosis, which translates to "living together," is prevalent in the natural world. For instance, certain butterflies depend on ants for their life cycle, while ants rely on fungi for their nests. Additionally, some fungi derive nourishment from plants, and specific plants depend on butterflies for pollination.

Forms of Symbiotic Relationships

Symbiosis manifests in three distinct forms:

1. Mutualism: In this scenario, both parties benefit from the relationship. A classic example is the clownfish, which finds refuge among the stinging tentacles of a sea anemone. The clownfish protects the anemone from predators, while the anemone provides safety to the clownfish.
2. Commensalism: Here, one party benefits without affecting the other. Examples include barnacles attaching to whales or orchids growing in trees, and seeds that cling to our clothing.
3. Parasitism: In this case, one organism gains at the expense of another. Approximately 40% of animal species are parasites, including hookworms, lice, and tapeworms.

Endosymbiosis: Living Within

Symbiosis can extend further to encompass endosymbiosis, where one organism lives within the tissues of another. A notable example is the eukaryotic cell's origin, which arose when an archaeon engulfed a bacterium. This successful merger led to significant advancements in cellular capabilities.

Photosynthetic Eukaryotes: A Case of Industrial Espionage

Consider this: why can plants perform photosynthesis while humans cannot? Both groups belong to the eukaryotic family, yet plants developed the ability to harness sunlight after diverging from the lineage that led to animals.

Interestingly, studies reveal that oxygenic photosynthesis emerged only once in evolutionary history, originating in a cyanobacterium rather than in a eukaryotic plant.

How do we reconcile this? The answer lies in endosymbiosis. At some point, a eukaryote engulfed a cyanobacterium, which established a permanent presence within the cell, enabling the eukaryote to photosynthesize.

This act could be likened to industrial espionage, representing a significant appropriation of the cyanobacterium’s intellectual property rights. Ultimately, plants are a combination of an archaeon, a bacterium, and a cyanobacterium.

Timeline of Endosymbiosis

The exact timing of this merger remains uncertain, with estimates suggesting it may have occurred around 1.6 billion years ago. However, the initial beneficiaries were likely microalgae, which began diversifying into early forms of modern red and green algae approximately 1.2 billion years ago.

Today, we might envision seaweed as sprawling fronds in rock pools, but these ancient algae were multicellular yet microscopic.

The Role of Fungi in Symbiosis

Endosymbiosis also played a role later on when a fungus fused with either algae or cyanobacteria to create lichen. The complexity of the natural world exceeds our imagination.

Plants rely on various symbiotic relationships, obtaining nutrients from mycorrhizal fungi, nitrogen from bacteria, and assistance in reproduction from numerous pollinators. Our survival is intricately linked to the existence of plants.

In conclusion, no life form can exist in isolation. All living beings are interconnected, emphasizing the idea that nature is a unified whole. Tennyson’s assertion about nature being a fierce battleground misses this essential truth.

This article is Part 35 in a series of 50 detailing Earth’s history, with each installment covering a 100-million-year period. For further reading, check out Part 34: REHEARSAL or Part 36: CYCLE. If you wish to explore the entire series, please follow my work.

Chapter 2: The Evolution of Photosynthesis

This video, titled "Evolution Revolution: SYMBIOTIC EARTH," delves into the intricate relationships among various organisms and highlights how these connections shape life on our planet.

Chapter 3: The Emergence of Lichen

The trailer for "SYMBIOTIC EARTH" provides a captivating overview of how symbiotic relationships have evolved over time and their impact on the environment.