But you're not talking about evolution then, but a Creationist strawman/misunderstanding of it. A cat giving birth to a dog would
falsify evolution.
Animals don't "produce different types of animals. I'm not going to go through the whole working, but take this link and it shows groupings of animals.
Animals
If you take the bilaterian link and follow down to Terrestrial tetrapods, you can see that even with modification and diversity, no group further out on the branches of the tree stops exhibiting the characteristics it shares with higher taxa. So even if a fish develops legs and lungs, it never stops being a Sarcopterygiian.
Sarcopterygii
Actually we can. First off, the fact that we trust decay rates not to suddenly change means we can have nuclear power. Second, we can study things like
the Oklo natural nuclear reactors and determine decay rates from 2 billion years ago. Just because
you don't know of or can't fathom a way to study the past doesn't mean others haven't figured out a way to already.
No. Viruses are a different type of life and some would consider them marginally life at that.
Apart from the new species you have been provided, we have many examples in the fossil record of transitional that exhibit characteristics of two taxa above species level. We even have some living beings that do the same for example Monotremes that have mammalian and reptilian traits. We also have living analogues for other transitional series for which we have fossils. Whales are a good example:
- Polar bears are land animals that are good swimmers
- Otters are land animals that are excellent swimmers
- Pinnipeds (seals, sea lions, etc.) are aquatic animals that function o.k. on land.
- Sirenians are aquatic animals that don't function on land, but stick to shallows.
- Whales are fully aquatic and exploit the entire ocean.
Now, whales didn't evolve from bears, but if we have analagous species existing today and fossils of similar transitional beings, what reason is there to reject whale evolution except incredulity?
There might or might not be a single common ancestor or ancestral species. Recent studies of bacteria show a lot of gene transfer. Once we get to metazoans (animals) it's pretty clear from the genetic evidence that we're all descended from an urmetazoan species.
If you want to look at how trees are related to other green plants read this:
Green plants
If you want to see how fish, dogs and cats are related take the Sarcopterygii link above, or if you just want dogs and cats they evolved from an urcarnivore.
Carnivora