Change in allele frequency over time.
Barbarian observes:
Different premise. That one is natural selection. And I’m sure everyone would like to see the flaws.
That is not true of all bees, only the ones that hive in great numbers. The loss of an individual is not a great thing for the hive, or even the individual, since all workers have the same genes. And losing the sting is quite advantageous to such an organism, because the sting apparatus continues to pump poison into the victim for a prolonged time.
They can’t live in all niches and other ants have evolved effective defenses against them.
It is a mammal. It has no bird apomorphies at all; the eggs are reptilian, not avian, and the “beak” is most like that of some extinct reptiles, not at all like the beak of a bird. It has no fishlike characteristics other than those found in other mammals. Exactly what you’d expect in a transitional between reptiles and mammals.
The extreme variations you see in Equus were induced by human intervention. There were much smaller horses in the wild millions of years ago, but they were not like the artificially dwarfed modern ones.
Barbarian, regarding polar bears:
Food to be had. Seals are pretty good prey. And the evidence is that they evolved during the last glaciation, which would favor such adaptations.
Brown bears live in Alaska now. And they take an occasional seal, when the opportunity arises. Polar bears use pretty much the same techniques.
Evidence. The two species diverged so recently, and are genetically so similar, that they can sometimes produce viable hybrids.
Barbarian observes:
Some did. For example, elephants tend to become dwarfed on islands. There are several examples of that. And some of the family, such as Hyraxes, got smaller and filled a different niche. Whales tend to be large because the environment favors larger animals with better heat retention. Selective pressures sometimes favor size, sometimes favor smaller sizes. Depends on the environment.
Small elephants would be less mobile. But food supply may be why they evolve to smaller sizes on islands.
Better at avoiding them, though. Fighting is not the only way.
Thylacines, for example. But they are now extinct. Pandas are less efficient predators, and are in considerable trouble.
Tends to. But that means that there are winners and losers. As conditions change, new winners and losers appear.
Dolphins are unable to efficiently exploit the large numbers of krill that are available to baleen whales, or to prey on the giant squid eaten by sperm whales. Each has it’s own niche.
Barbarian observes:
They aren’t. Chimps are far more like us than pigs.
viewingspace.com/genetics…rd_piglets.htm
Your link doesn’t say what you claim it does. In fact, it says that humans are more like primates than pigs.
All it says is that pigs are about the same size as humans, and that genetic manipulation to make pigs immunologically acceptable to humans might permit tissue or organ transplants.