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  • He's a cold-hearted snake (OOO) look in to his eyes. Uh-oh. He's been lying on a rock

  • to get warmth from his environment.

  • Sup meatbags, Trace here for DNews to talk about why you're all SO HOT. But really, you're

  • hot. Have you ever thought about why? Thermoregulation. Science divides thermoregulation into endothermic

  • or ectothermic; homeothermic or poikilothermic (poiˈkēləˌTHərmic). Endo and ecto thermic

  • describe an animal that either makes it's own heat or gets it from the environment.

  • Homeo and Poikilo describe whether the temperature is constant.

  • A cute siamese cat is an endotherm and homeotherm, it makes it's own heat, and maintains a constant

  • body temperature; most mammals and birds are endothermic homeotherms -- what elementary

  • school would call warm-blooded. Fish, amphibians, reptiles and most invertebrates are ectothermic

  • poikilotherms; they get heat from the environment and let their body temperature fluctuate -- what

  • the youths would call cold-blooded. But that's only part of the picture! They make their

  • own heat, but don't always maintain it. Some fish maintain a constant temperature and create

  • heat by swimming from cold to warmer water, but can't generate it themselves; leatherback

  • turtles and lamnid sharks do this too! All I'm saying is, it's a wider world than the

  • black-and-white of cold versus warm blood!

  • But that's not all! Dinosaurs used to be thought of as cold-blooded terror lizards that would

  • obviously make AMAZING PARK ATTRACTIONS DON'T WORRY NOTHING COULD GO WRONG. // But a study

  • in Science found dinosaurs were likely mesotherms -- they used a combination of internal processes

  • and environmental factors to adjust their overall body temperature! Plus, animals that

  • hibernate like chipmunks and some bats are heterothermic! Whew. Yeah, It gets confusing,.

  • The reason we simplify it to warm and cold blooded is because temperature, which is mainly

  • circulated by the blood, affects things like muscle function and brain size. Colder muscles

  • react slower, meaning ectothermic animals have to behave sluggishly when the environment

  • is cooler. They have no choice! Even if a predator is around. According to Spring and

  • Holley's Introduction to Zoology, with a 18 degree F (10C) change in temperature, muscles

  • contract three times faster, pulling three times the power. Knowing this, you can understand

  • why yellowfin tuna evolved to be poikilotherms! Warmer muscles react better, allowing them

  • to keep their bodies at a slightly higher temperature than the surrounding water; thus

  • they maximize their power and catch prey.

  • Mammals and birds range in temperature from 97 to 104F (37-40C) and that has a cost; we

  • have to eat to live and regulate metabolism! Pandas spend 10 to 16 hours a day eating,

  • and the British Medical Journal recorded hunger strikers who lasted 40 days without food.

  • But that's child's play; pythons can go a year between meals. So why aren't we just

  • SLIGHTLY regulating our temperatures like tuna? Seems like a big waste to burn all that

  • energy and stay hot all the time, right?

  • All that heat keeps our muscles ready for action. Endothermic animals can almost always

  • outrun ectothermic animals; assuming they survive the initial strike. Ectothermic animals

  • are better at that initial attackthink a snake or fast-fish! Insects with cold muscles

  • can't fly, the Sphinx Moth vibrates its muscles before takeoff to get them warm. Plus, cold

  • animals may miss opportunities to use their muscles to get all up ons and mate! Warm-blooded

  • animals can mate ANYTIME. Whichyou know. That's fun. PLUS all that energy and heat

  • allows for the evolution of more complex brain structures, which allowed me learn to talk

  • to you right now!

  • That being said, it's hot. It's real hot. And sometimes it's just TOO hotor too

  • cold! So animals that evolved to be homeothermic -- maintaining temperature -- had to ALSO

  • evolve fur or blubber to stay warm and sweat glands or panting to cool off. But that's

  • a whole other video. Want to know why we sweat and how AWESOME we are at it? Check out this

  • video Do you have a science question you want us to answer? YouTube gave us the comments for a reason,

  • so y'all could troll, but you could ALSO use them to ask me a science question. Maybe try

  • that? And please subscribe! We're here every day for our subscribers, and I love my job.

  • So from the bottom of my heart, thanks!

He's a cold-hearted snake (OOO) look in to his eyes. Uh-oh. He's been lying on a rock

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