This leaves me wondering if the lizard somehow 'knows' what mutation should occur to make it more adaptable, the chances of all these mutations such as eyes, wings, arms, etc being 'random' and continuing to improve through random mutations seem too low to me.. perhaps there is another force of evolution which dictates that some mutations which increase the species' survival have to occur and its not completely random.
No. Mutations are completely random. It is just that only those that are somehow helpful in the current environment will live on. Then all these small helpful mutations add up to make a big improvement.
Imagine the following experiment:
We take a million people and put them through a series of experiments. At each stage, every person has to role a dice. In the first experiment, all people rolling a 5 survive, all others are killed. In the second experiment, all people rolling a 2 survive, all others are killed. In the third experiment, all people rolling a 1 survive, all others are killed. In the fourth experiment, all people rolling a 5 survive, all others are killed. In the fifth experiment, all people rolling a 1 survive, all others are killed. In the sixth and last experiment, all people rolling a 6 survive, all others are killed.
After that, you have probably around 30,000 people left of the originally one million. All of those people have rolled the sequence 5-2-1-5-1-6. You can now ask. How did those people know they had to role this special sequence? Their dices cannot have been random dices, because how else would the dices know what number to role?
But this is the wrong way of approaching this. The 30,000 people remaining were just lucky. There are 970,000 people that were unlucky. They rolled the wrong numbers, so they are dead now.
It is the same with mutations: There is lots of different mutations. You don't see many people around with harmful mutations because the mutations being harmful means they won't live or won't have so many children. So, these mutations don't survive, while the beneficial (or neutral) mutations survive.
Not let's return to the lizard species that adopted to be able to eat a certain kind of plant. You may ask: Why did the other lizards on the continent not also evolve this ability? Certainly, this ability is not harmful. All these mutations are not harmful, because they help the lizards on the island to survive. But this thinking is wrong, because you cannot judge whether a mutation is harmful or helpful without considering the environment.
The mutations that lead to the lizards being able to eat that special plant probably are harmful in a normal environment where other plants are there to eat. How are they harmful? They probably mean that the lizard body has a feature that costs energy.
In a normal environment, the ability to eat the special plant (when the plant is not there) is a disadvantage because it means wasting energy on a feature you never need. In an environment, where the plant is present (and especially when there are few other edible plants), the ability to eat that plant is an advantage. So in the latter environment, such mutations would survive, in the former environment, such mutations would not survive.
Now you could again ask: How do the lizards on the continent know that evolving such a feature would be a waste of resources? And again, they don't know that. It is just that animals wasting resources have a higher chance of starving than animals not wasting resources. So, if there are any animals that evolve mutations towards being able to eat that special plant in an environment where that plant doesn't grow, when the next time of few resources comes along, they will probably be the first ones to starve, i.e. they will over a long period of time not have many surviving offspring.
Topic: Some questions about evolution