In the movie the Matrix Agent Smith said something like, 'all animals strive to find a natural 'equilibrium' with there environment ,... a harmonious existence with their ecosystem', ( forgive misquoting). Is this true that each animal 'does' a lot of activity whether by instinct or an ad-hoc form of 'simple' planning to 'cooperate' with it's environment ,or exist 'harmoniously with it?
The answer to the question as stated is, certainly: No. Neither on a conscious level, nor at the level of instinct does an animal have the goal of keeping the ecological balance of its environment intact. Quite the opposite: it is constantly trying to overturn that balance, attempting to change the system and bring it to a new situation, one in which it (the animal) and its children have a higher survival and procreation chance than the current one. Whether the new situation will be stable (= a balance) or not is not a criterion, and cannot be predicted by any animal acting on the environment (including the humans).
To use an example: As the news outlets have been warning us in recent years, if all bees were to die, our whole ecosystem could collapse. Yet no bee is pollinating flowers because it somehow feels that this will prevent the collapse of the current ecosystem. It gathers pollen because its swarm is hungry.
There is also nothing "natural" about the equilibrium our ecosystem is in, at least not in the sense implying that "this is how it should be, and everything else is so bad that it goes against the very laws of nature". It is just one random equilibrium of many possible states of our planet, some including an ecosystem in equilibrium, others including self-destruction of the ecosystem. All of these states are equally natural, and the planet has passed through several of them before establishing the current one (which isn't about to stay here forever either).
There is a purely philosophical issue behind your question. What does trying mean? Does trying doing A means that an individual is aware of how to achieve A and will behave so to achieve it?
The likely correct answer (it really depends on you definition) is "No" (with some eventual exception among those that have high cognitive abilities such as humans). No, animals don't try to create a nice ecosystem. Animals (just like any living things) just evolve in response to their environment and this ends up creating ecosystems. The ecosystemic balance is just the result of the non-cooperative actions of the different species at play in the ecosystem. For example, animals reject nitrogen not in order to help plants to grow but only because nitrogen is a waste and is toxic for them. You may want to make you understand how evolution works.
For those who have a good enough knowledge in evolutionary biology, I have to admit that the above answer might be slightly wrong if we consider some special kinds of selection such as kin selection, species selection or even ecosystem selection. I think the answer to the question remains "no" given the "conscious" side of the definition of trying that the OP was probably using.
Cooperation is easy to explain, real altruism is more complicated. Real altruism is when one individual makes an action that benefits to the others lifespan reproductive success but decreases the lifetime reproductive success of the one producing the action.
Within population real altruism can be explained by kin selection. see this post for more info.
Between species real altruism is much more complicated to explain. It would need to use concepts such as species selection. But does between species real altruism even exist (beside some behaviour from species with high cognitive abilities)? I don't think so.
What you are interested in is inter/species cooperation. Very often the individual that offers something to the other also directly gain something. For example, the animal excrete nitrogen because it is toxic and the plant take advantage of this. But sometimes an individual (actor) pay a cost for producing something to the benefit of the other individual (recipient). In return, the actor will receive something back from the recipient. For example, in the lichen, the algae offers energy while the fungi offers shelter. If one stops the other will die and both will lose. There are known cases also where individual A stops offering goods t individual B if individual B stops offering goods to individual A. This kind of traits are best studies with the tools of game theory.
There are many, many examples of species in their native environment accidentally destroying their ecosystem when external factors constraining their ability to reproduce are removed. For example when wolves and other large predators were removed from most of the American west ungulates like deer and elk nearly stripped the environment bare, to the point that riparian lowlands were completely stripped of vegetation and native willow populations were severely effected.
Similarly, invasive species, when introduced, aren't intentionally trying to drive other species to extinction, it's just that their adaptations are so mismatched the invasive species succeeds disproportionately often allowing for a population boom. For example, sea lamprey weren't trying to wipe out lake whitefish and lake trout when they got into the Great Lakes, they were just too good at what they did.
Even in humans "living in balance with ones environment" is a rare idea, and generally only occurs in populations that have the resources to spare and don't have to worry about their own survival.