I must have missed your post. Evolution does not prohibit morality.
Then what did you mean by this:
Exactly. If evolution is true, there is NO basis for morality.
The above statement implies that one cannot be moral if they accept evolution as being factually true.
However, if survival is the name of the game, how come those who struggle are not permitted to do what ever it takes to survive?
For starters, science is descriptive, not prescriptive. Since you're probably looking at science and evolution through the same lens as you would look at the Bible, you're expecting science to dictate behavior. That isn't what science is for; it's simply meant to describe things as they are, not prescribe behaviors.
Second, people are often put in situations where they do whatever it takes to survive regardless of moral compass. Put a person in a desperate situation and you'll see how quickly they adhere to their prescribed morals. This is the basis of many moral dilemmas.
Finally, humans are social creatures. We benefit from cooperation. Engaging in behaviors that foster cooperation can result in beneficial outcomes that are greater than engaging in strictly selfish behavior. But as per above, it can come down to individual circumstances.
On that note, I'll leave you with the Heinz dilemma:
A woman was on her deathbed. There was one drug that the doctors thought might save her. The drug was expensive to make, but the druggist was charging ten times what the drug cost him to produce. He paid $200 for the ingredients and charged $2,000 for a small dose of the drug. The sick woman's husband, Heinz, could only had $1,000. He told the druggist that his wife was dying and asked him to sell it cheaper or let him pay later. But the druggist said: “No, I discovered the drug and I'm going to make money from it.” So Heinz got desperate and broke into the man's laboratory to steal the drug for his wife.
Was Heinz in the wrong to steal the drug to save his wife? What would you do in this situation?