For example, in the co-evolution of plants and insects, birds or any other organism that pollinates it, the mutations they acquire with time are merely by chance or are there some signals which lead to positive mutation whereby it depends on the interaction with environment for better survival?
There are two processes, one random and one not. Mutation is generally held to be random. I suppose there is the possibility of relaxation of some system of protection against mutation to change the rate, and that may be out there but I haven't seen it (not really my central interest). But generally, mutation is random. What is not random is selection, and that is the interaction of the genome, via the phenotype, and the environment. So it is probably not constructive to speak of a mutation being non-chance unless you refer to the mechanism that might allow that, if any exists.
There are known mechanisms of biased mutation rates, spots, regulation, etc. that are results of past selection on the plasticity and evolvability of organisms and populations. There is also physico-chemichal bias on mutation. But the outcomes continue to happen probabilistically and the effects on fitness depend of a new round of selection to produce adaptation.
Some confusion arise because two class of errors:
1 – Conflation of mutation being random in relation to fitness and random as a molecular event.
2 - Confusion between randomness with equiprobability. Mutations don’t have to be equiprobable to remain random in origin. It's enough that they have any probabilistic distribution - i.e. are not detereministic.
There are evidence of coevolutionary scenarios between parasites-hosts where mechanisms of biased mutation/mutability are known on bacteria, mainly for traits related to bacterial resistance and responses to stress. This is less likely in multicellular organisms, mainly on those with a rigid division of soma and germ-line tissues.
Mutations themselves are random and fix in the population with different probabilities. For example, the probability of fixation of a neutral mutation is 1/2N. A mutation can fix randomly in a popation through drift or through selective processes, and is dependent on the effective population size, strength of selection/selection coefficient, and if the mutation is dominant or recessive. You should give this online book a read over, https://www.google.com/url?sa=t&source=web&rct=j&ei=ONh2U5aUNsyMqAbA64CACw&url=http://evolution.gs.washington.edu/pgbook/pgbook.pdf&cd=1&ved=0CCQQFjAA&usg=AFQjCNHzXwoUZpFS8eYLfWXdxr7bvOJEqg. You might also want to consider reading more on fitness landscapes, and as mentioned in previous posts coevolution of traits (or from a molecular biology point of view, amino acid changes).
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