resting potential

Resting potential is maintained in all cells not just excitable cells like neurones. It is mainly mediated by potassium movement into and out of the cell. the inside of the cell contains a lot of potassium which  has a single positive charge, this is balanced by various negative anions in the cell. The fluid around the cell contains very little potassium creating a chemical gradient. As the potassium passively diffuses out the cell down its chemical gradient the negative charges on the anions are no longer balanced. This makes the inside of the cell more negative than the outide of the cell. The sodium potassium pump uses ATP to transport potassium and sodium against their concentration gradients, 3 sodiums are moved out of the cell for every 2 potassiums moved into the cell. This helps to maintain the resting potential charge but does not create it. This occurs in every cell in the body.

Spot the intruder

Blue-Headed Wrasse

These crazy fish all start as females as only large fish can defend their territory. As young fish are obviously smaller they all start as females and only turn to males as they grow and become able to defend their territory! This is called protogynous hermaphroditism, beginning as females and becoming male.

picture by Richard Seaman

The Female Hyenas Pseudopenis!

Female Hyenas have evolved the crazy structure of a pseudopenis. It not only looks exactly like a male penis it can also become erect. It is actually evolved from an extended clitoris which is made of the same embryonic tissue as the penis.  The pseudopenis stumped scientists as it is such a costly adaptation, 10% of female hyenas die in childbirth as they have to push the pups down the narrow tube of the pseudopenis! It turns out that penis presentation is important in submissive displays between subordinate females and dominant females.

Mobbing

Little birds like blue tits, woodpeckers and crows repeatedly dive on big birds of prey when they're not in flight to bully them into leaving. Often done to owls who are too sleepy to move away in the daytime. It can stop the chicks being preyed upon, although it takes lots of energy and can attract other predators. Blue tits have a special cry when they see a predator, if the predator is perched the blue tit will let out a call to arms to nearby blue tits and mob the stationary bird. If, however the bird is in flight it presents more of a threat and the blue tit will warn nearby birds with a call called a seet. A seet is a call that is much harder to pinpoint the source so presents less risk of the blue tit being detected

picture by Nigel Barker