The animals could change it. For example, a bunny could dig a hole in the ground, making a home for other animals inside of it, too, changing the animals' living environment.
Or natural disasters could change their environment, too. For example, if a landslide occurred and covered a pond, frogs and snakes could lose their living areas and food, which would make them have to move to a different area, changing another ecosystem.
Answer: Because Watson and Crick were stealing the ideas that she made. And because if she did share it everyone would probably only acknowledged the two men and NOT Rosalind Franklin.
