Nature doesn't re-write genetic codes, it decides which genetic codes will succeed or fail. For instance, the arid environment has decided that most hairy mammals will fail in that environment, which is why you don't typically see hairy mammals in the desert, except for the camel, a creature that evolved to succeed in the arid environment. So the arid environment has decided that camel genetics are successful.

(of course I'm talking as if "nature" is a conscious entity, which it is definitely not)

You also don't see reptiles in polar environments, because that environment selects only creatures who can thrive there, such as hairy mammals, like polar bears and elk, and penguins, sea lions, etc.

Genetic mutations add new genes and new combinations of genes to the DNA. But also the mechanisms in which certain genes express themselves can also change too. Getting into genetics is kind of complicated, but the mechanism of natural selection is incredibly simple.




When hundreds of adaptations build up over time, then yes it can transform a creature into an entirely different one. Correct, there is not a single "half this, or half that" fossil. There is no half-horse, half-pig fossil because evolution doesn't happen over night.

When gradual genetic changes accumulate over tens of thousands of years, then you can end up with a new species.

Also, there are many transitional fossils which display a subtle mixture of traits that are found in a variety of animals, like birds, reptiles, mammals, etc.

For instance, Tiktaalik:
[link to evolution.berkeley.edu]

The duck-billed platypus:
[link to www.sciencedaily.com]

Even penguins are a great example of a living transitional species. They evolved from flying birds, which explains their wings and beaks, but over time they adapted to a colder and more aquatic environment, eventually evolving into a flight-less species.



The makes absolutely zero sense.

Seasonal changes are minor compared to dramatic climate changes, like asteroid impacts, massive volcanic eruptions, and the drifting apart of the continents. All of these dramatic changes occurred over the eons. And as we can tell by the fossil record, millions of species went extinct because they could not adapt fast enough to swift changes in the environment. Fortunately some creatures were able to adapt to dramatic changes. So just having the capacity to adapt to seasonal changes might be sufficient in a very stable world, but our world is definitely not stable. It can change dramatically over time, which is why creatures require the capacity to evolve, otherwise they would become extinct.