Well, animals are PART of the ecosystem. Individual, population and community (an animal, group of individuals of the same species in a specific environment, group of individual of every species in a specific environment) of animals are just different levels of biological organization.
Also, we should start by clarifying what "help" means. I will assume it means "engages in physical work which ends up allowing the destination or 'helped' system to continue its usual course or keeping its characteristics between certain parameters".
Having both things in mind, we can answer to your question by saying that every individual performs actions (except in extremely rare cases, like an arsonist) which end up allowing other organisms to thrive. Such actions vary from ecosystem to ecosystem. An example would be archeobacteria metabolizing chemicals that are hazardous to the other living things into digestable or breathable material. Plants, another example, transform animal-poisoning CO2 into animal-breathable O2, while animals do the same the other way around.
However, some tasks involve necessary death. Such is the case when a cheetah hunts a gazelle down. Thus, the cheetah feeds her offspring, while enabling the carcass to be eaten by scavengers and decomposers and prevents the grass from being over-eaten by the local gazelle population, which would cause the other herbivores (and other gazelles) to starve.
You should not think of "animals helping the ecosystem" like you do of giving donations to hurricane victims across the world. Think of it instead as a part in a play or a job in a big corporation.
Cheers and greeting from Perú. We REALLY like your food.