Everyday Biology: Did You Know? – Part 1

[C] AIDS | Disposable syringes keep you from catching blood bugs like HIV, hep B, hep C—stuff that rides a dirty needle in a heartbeat.

[C] Deoxyribonucleic Acid | Think of it as the world’s longest IKEA manual, written in only four letters and crammed into every microscopic cell.

[B] Karl Landsteiner | Before he spoke up, getting a transfusion was like playing Russian roulette with your veins.

[B] Human skin | Your 20-square-foot birthday suit that quietly swaps itself out every month, so you’re basically wearing a fresh hide 1,000 times in your life.

[A] Adrenaline | The 60-second “HULK MODE” button: lift cars, outrun dogs, then wonder why your hands won’t stop shaking.

[A] Stapes | Smaller than a grain of rice, cranks up sound 20×. Without it, everybody sounds like the teacher from Charlie Brown.

[C] Insulin | The little doorman that escorts sugar into cells. In diabetics, the doorman either quits or needs a hearing aid.

[C] Iris | It’s just melanin interior design. Blue eyes aren’t actually blue; they’re brown eyes with the lights off.

[A] BCG | A cow TB strain turned vaccine—basically the first time cattle taught humans how to stay alive.

[C] Femur | Handles 30× your weight and only reminds you it exists when you ram it into the coffee table.

[A] Charles Darwin | Sat on the idea for 20 years because he knew it would break the internet of 1859.

[C] Thallophyta | The ultimate plant minimalists; they basically stopped at “green blob.”

[C] Ligaments | Stretch one too far and you’ll be explaining for weeks how you wrecked yourself tying your shoe.

[B] Plasma | 92 % water, 8 % DoorDash for your cells.

[A] Mosquito | Packs 47 mini-saws to slice your skin, then throws in free anticoagulants. Thanks, nobody asked.

[D] Eye | They widen when you see someone cute, so yes, your eyes literally snitch on your crush.

[A] Convex lens | Flexes 100,000× a day so you can binge-scroll without moving your head.

[A] Testosterone | Morning spike that powers both dawn ambition and questionable power-tool purchases.

[D] Liver | When it slacks off, bilirubin throws a yellow party and you become the highlighter no one asked for.

[D] Rod-shaped | Tiny edible-looking cylinders; some spoil the cookout, others ferment your yogurt.

[B] Vena cava | Garden-hose-wide freeway that ships every drop of blood back to heart-central.

[A] Brain | It’s the VIP screening room, not the camera; zero pain receptors, so surgeons can poke it while you’re still chatting.

[B] Monosaccharide | Brain’s favorite candy; 20 % of your sugar budget feeds the 3-pound blob doing your homework.

[B] Epidermis | Basically dead-cell roof-shingles; you’re literally wearing last week’s corpse dust.

[D] 22 | Jigsaw pieces glued with “suture” stickers; babies start with extras that fuse like biological IKEA.

[D] Ethanol | The only one that won’t blind you. Liver’s pace: one drink per hour, no matter how cute the bartender is.

[B] Polynucleotides | Four-letter alphabet chained together; 99.9 % identical across humans, so all our drama lives in the remaining 0.1 %.

[B] Hansen’s disease | Hard to catch; 95 % of people are naturally immune—history’s most overrified panic.

[D] Ductless glands | They FedEx hormones straight into blood—no tubes, no address, just “hope it finds you.”

[D] Amphibious plants | Moss squad that can’t reproduce without water; helicopter parents who make their kids swim before they’re born.