What is the Smallest Organism on Earth? | Wonders of Life w/ Prof Brian Cox | BBC Earth

Summary

The video explores the significance of bacteria, the oldest and most abundant life forms on Earth, exemplified by thrombolites found in Lake Clifton. It explains how these simple, microscopic organisms are structurally distinct from animals and plants and dominate life on the planet. With sizes around 2 microns, they vastly outnumber human cells. The video discusses the physical limits on the size of free-living organisms, suggesting a minimum size of about 200 nanometers for viable life. This principle is believed to apply universally to carbon-based life forms, highlighting the fundamental properties of the universe.

Takeaways

• 🌍 Bacteria are the oldest and most abundant forms of life on Earth, dominating nearly every ecosystem.
• 🦠 Thrombolites, unique rock-like structures formed by bacterial colonies, can be found in shallow waters like Lake Clifton in Australia.
• 🔬 Bacteria are not classified as animals or plants; they belong to their own unique taxonomic kingdom.
• 📏 Bacteria are incredibly small, typically around 2 microns in size, allowing for hundreds of thousands to fit on a pinhead.
• 💡 When scaled up, a single bacterium can be visualized as being about 25 kilometers tall compared to a coin.
• ⏳ Bacteria were the first life forms on Earth and have persisted throughout the planet's history.
• ⚛️ The smallest size limit for free-living organisms is determined by fundamental physical laws and properties of the universe.
• 📐 The minimum size for a free-living organism is calculated to be around 200 nanometers, applicable to any carbon-based life form across the universe.
• 🌌 This size limitation for life is believed to be universal, not just specific to Earth.
• 🔭 Understanding bacteria helps illuminate the broader principles of life and the physical laws that govern existence.

Q & A

What are thrombolites and how are they formed?

Thrombolites are rocky formations created by colonies of microscopic bacteria. They are built up over centuries and have a clotted structure, often found in shallow waters like Lake Clifton near Perth.

Why are bacteria considered the oldest and most abundant life forms on Earth?

Bacteria are regarded as the oldest and most abundant life forms because they were the first life forms to appear on Earth and they continue to dominate various ecosystems, existing on nearly every surface and environment.

How do bacteria compare in number to human cells in the human body?

There are more bacterial cells living on and inside the human body than there are human cells, highlighting their significant presence in our biological makeup.

What is the typical size of bacteria?

Bacteria typically measure around 2 microns, or 2 millionths of a meter, which is so small that approximately half a million could fit on the head of a pin.

How does the size of a single bacterium scale up for visualization?

If a single bacterium were scaled up to the size of a coin, it would be approximately 25 kilometers high, demonstrating just how tiny bacteria are.

What distinguishes bacteria from animals and plants?

Bacteria are structurally much simpler than animals and plants and are classified in their own unique taxonomic kingdom, separate from these higher life forms.

What limits the minimum size of free-living organisms?

The minimum size of free-living organisms is limited by the need to accommodate all the molecular machinery necessary for life, which is influenced by the laws of physics and the size of molecules and atoms.

What is the calculated minimum size for a free-living organism?

The calculated minimum size for a free-living organism is around 200 nanometers (200 billionths of a meter), which is believed to be a universal principle applicable to carbon-based life throughout the universe.

Why are bacteria considered to play a crucial role in ecosystems?

Bacteria are essential for various biological processes, including decomposition, nutrient cycling, and as a foundation for food webs, thereby playing a crucial role in maintaining ecosystem balance.

How do fundamental properties of the universe affect the size of living organisms?

The fundamental properties of the universe, such as the strength of electromagnetic forces and the mass of electrons, determine the size of atoms and molecules, which in turn dictate the minimum size of living organisms.