... Or take an animal and see if it 'evolves' into a different animal. ...
GeoffP has given a recent example:
There is the well know example of a white moth that was common in England before the industrial revolution, but became grey in less than 100 years of negative selection against the white ones in very polluted (by dark coal dust and smog) London air. (Birds found and ate the white ones much more easily on the sooty surfaces.) BTW, now that the coal soot is not part of London’s air the white moth variation is again dominate.
Also some decades ago in Brazil some of the small fish, which reached sexual maturity in about a year and laid a few eggs because they were often eaten by the larger fish that also lived in a stream below the waterfall were move above the water fall. Then evolutionary selection favored those that delayed sexual maturity and grew much larger, and laid many eggs. (They did not need to quickly reproduce a few before they were eaten.) In about 10 years, the now above water fall fish were several times larger with sexual maturity coming at about 3 years of age and rapidly growing in numbers in the environment free from predators that lived below the falls.
I think this dramatic change in size, age of sexual maturity, and egg laying in only 10 years may be the shortest known demonstration of evolution in large, complex animals.
There are millions of examples of single cell animals that have evolved when their environment has been changed. - You almost certainly have run such an experiment yourself, if you have ever taken an antibiotic. (A drastic change in the germ's environment.)
The reason you are told to continue taking many days after you are "cured" is that some of the bacterial are evolving resistance to it. If you stop when "cured" their numbers will grow and you will be sick again. The common use of anti-biotics in animal feed etc. has evolved germs that are now immune to the three most common types of anti-biotics - It is a very serious problem - a war between man and germs and in the long run it appears as if the germs are using evolution to win the war.
I have also posted about the “Santa Catalina guinea pigs.” They are few in number (about 40 – all the vegetation of their tiny, mainly rocky off shore island will support) and the only mamuals on the island. That Island was once (during last ice age when sea level was much lower) connected to the Brazilain mainland. They are less than half the size of the mainland guine pigs they evolved from (limited food favored the smaller body) and have evolved several other physical features that aid them to survive on this tiny, rocky off shore island, but I forget the details. – find my prior posts.
In fact there are many dozens of examples of multi-cellular animal evolution that have been well documented.* In some cases the environmental change that caused the selection of a new form was an intentional experiment; in some cases the environmental change was man-made but mot done to demonstrate evolution, (Industral soot in Londond); and in some cases, man had nothing to do with it (ice age lowering of sea level, cutting off a small group and stressing them differently with limited food supply and no predators so population was limited only by the food supply - the smaller individuals were selected for.)
*Your ignorance of the facts does not disprove the fact of evolution. With litterally millions of demonstrations of evolution, it is hard to understand how you can be so ignorant.