The fittest survive, but what does that mean?
Even now there are still people who do not fully understand the tenet of the survival of the fittest and believe it has something to do with winners and losers of a combat and physical strength. However, that even the smallest individual could be the fittest individual perhaps under conditions of a food shortage or an availability of shelters best suitable for small individuals and that an individual which is weak, but smarter than others could become the “fittest” through the process of selection is something that needs to be emphasized. To explain natural selection, zoologists often use the example of the white and dark specimens of the peppered moth Biston betularia in England: the originally rather rare dark variety became increasingly more common as industrial pollution increased and the whitish tree trunks of birch trees turned grey with soot. When pollution levels subsided and the environment became cleaner again, it was the lighter coloured variety that gained the upper hand once more.
Swimming in Air
Anyone who has ever seen some video footage on how the marine snail known as the “Spanish Dancer” (Hexabranchus sanguineus) or such dorso-ventrally flattened fishes like skates and rays move under water (the manta ray, often even leaping into the air) or how penguins dart through the water in pursuit of little fish will agree: they fly under water.
Increases of some structures appear to parallel decreases in others
It seems odd, but no animal with horns or antlers, whether fossil or recent, has all the teeth required to give it the complete and full dentition characteristics of mammals. No species of spider is known to possess the ability to sting, but all have a poisonous bite (although, luckily only a few possess poisons potent enough to harm humans). The most colourful birds like tropical parrots and Papua New Guinea birds-of-paradise leave a lot to be desired when it comes to their ability to sing and the increase in swim speeds of fish like the tuna apparently went hand in hand with the loss of the buoyancy organ, the swim bladder. There are lots more of such examples, but what am I trying to demonstrate with these examples? I’m trying to show that the development in one area frequently has consequences in another and that a “push” in one evolutionary direction can see a reversal in another. —>—>