Answer:
The Struggle for Survival refers to the fight between organisms to survive by having access to the increasingly scarce resources in the environment brought upon by population increase.
Darwin believed that evolution was brought about by external pressures arising from this struggle for survival as species would have to adapt to the unique challenges in their environment to be able to better access resources.
This is why one must understand the challenges in an environment to understand why species in that environment evolved the way they did.
