Why is some hair curly and some hair straight?
Humans have a huge variety of hair types. Like all of our other physical and internal characteristics, hair structure is also mostly determined by our DNA, the blueprint for everything that makes up our body. Keratin, a protein that makes up our hair and our nails, differs in structure in curly and straight hair follicles. In straight hair, the keratin is symmetrical in structure, while in curly hair the protein is unevenly distributed. Asymmetrical hair creates an oval shape and curls more as the hair grows, while symmetrical hair grows round and straight. Cellular receptors on the outer side of a hair follicle are also known to determine hair growth. Certain cancer drugs have caused straight hair to turn curly because they inhibit certain cellular receptors controlling hair follicles.
How are cats always able to land of their feet?
Cats are able to land on their feet because of their “cat righting reflex.” Their ability for this reflex stems from their incredibly flexible spines and lack of functional collarbones. There are four steps that cats do to land on their feet. First, they figure out which way is up either visually or using their inner ear. Second, they bend their backs at a large angle. Then, they tuck in their front legs and extend their back legs so they can rotate their front half to be upright. Finally, they extend their front legs and tuck their back legs so their back half of their body rotates to align with their upright front half. This quick succession of events is what allows a cat to twist and rotate their bodies so they land upright. However, that doesn’t mean they’re prevented from getting injured! While a cat has several physical features to reduce the intensity of the impact, they can still break bones or even die when falling from high enough heights. There is some research showing that they start to suffer significant damage when falling from heights of five to seven stories. Nevertheless, their ability to land on their feet is still extremely impressive in the animal kingdom.