How did Darwin arrive at the idea about species variation

We can see some of the most important patterns Darwin noticed in distribution of organisms by looking at his observations of the Galápagos Islands off the coast of Ecuador. Darwin found that nearby islands in the Galápagos had similar but nonidentical species of finches living on them.

advantage of using stem cells in medical research:

1.       it provides medical benefits in the fields of therapeutic cloning and regenerative medicine.

2. it provides great potential for discovering treatments and cures to a variety of diseases including parkinson disease, spinal cord injuries, diabetes, alzheimer’s disease and many more.

3. limbs and organ could be grown in lab from stem cells and then used in transplant or treat illness.

i don't know. if i were you, i would search it up online : d