Genetic variation is when there are many offspring with different genetics, therefore some offspring might be able to adapt due to its genetics
i) Because the worms would have either learned to become night worms or all day worms would have been eaten faster than they could reproduce
ii) Natural selection. Humans had no interaction with which worms survived, so it's all natural.
I hope this helps! Good luck!
Natural Selection, Charles Darwin coined the term “survival of the fittest”
Dissection is ethically and socially against humans