Biology facts

Explore 10 curated biology facts on ScienceCards. Discover surprising, well-sourced science one card at a time.

• Sharks (450 million years old) have existed for two… — Sharks (450 million years old) have existed for two galactic years—our solar system has orbited the Milky Way twice since they appeared. They predate dinosaurs and are older than trees.
• Electric eels have 6,000 electrocytes—muscle cells that… — Electric eels have 6,000 electrocytes—muscle cells that produce voltage—stacked in series, generating 860 volts. Enough to stun a horse. Volta copied this design in 1799, inventing the first battery.
• After 30-40 minutes in darkness, your eye's rod cells can… — After 30-40 minutes in darkness, your eye's rod cells can detect individual photons—the smallest unit of light. Your eye operates at the theoretical limit; it cannot get more sensitive.
• Every breath you take is thanks to bacterial waste. — Every breath you take is thanks to bacterial waste. Cyanobacteria spent a billion years releasing oxygen as a toxic byproduct. The Great Oxygenation Event killed most early life—survivors adapted.
• An adult human has 10 quadrillion mitochondria that produce… — An adult human has 10 quadrillion mitochondria that produce approximately 100 watts of power at rest—enough to power an incandescent light bulb continuously.
• An octopus has ~180 million neurons in its brain and 320… — An octopus has ~180 million neurons in its brain and 320 million in its arms, which think semi-independently. They use tools, solve puzzles, recognize faces, learn by observation, and play.
• Origin-of-life research studies the most mysterious… — Origin-of-life research studies the most mysterious transition in Earth's history: from chemistry to biology. Around 4.2 billion years ago, molecules became life—and we still don't know how.
• Your brain is only 2% of your body weight but consumes 20%… — Your brain is only 2% of your body weight but consumes 20% of your energy. If your body burns 1,800 calories per day at rest, your brain uses 360 of those calories.
• Sea turtles navigate thousands of miles using Earth's… — Sea turtles navigate thousands of miles using Earth's magnetic field as a biological GPS. They detect both intensity and angle—hatchlings reorient instantly when researchers shift the field.
• 3,000-year-old honey found in Egyptian tombs is still… — 3,000-year-old honey found in Egyptian tombs is still edible because honey’s low water, acidic pH (~3.2–4.5), and glucose oxidase enzyme produce antimicrobial hydrogen peroxide, preventing spoilage.