The muscular system consumes a lot of oxygen and water in its cell respiration. to keep the muscle functioning. the muscle finds resources in the ecosystem. with out the proper ecosystem the muscle would not have enough water or oxygen for the cells to survive and you would slowly starve.
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Proper Ecosystems
Will have plenty of water from a fish stream or fast moving river, and lots of nutrients, from plants and animals for meat. For example there might be some coco nuts in trees or some potatoes in the ground or maybe some rabbits and beaver to hunt for meat.
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Improper ecosystem
A desert would be a good example of a poor ecosystem, with out the shelter of shady trees, your bod would begin to sweat. and with out the fresh water supply you would slowly starve to death. And animals an plants being scarce you would have no food. leaving your muscles without proper nutrients they would soon lose there strength and your movement would begin to come to a halt and you would be trapped.

Conclusion: the ecosystem can be more important then any other organ when it comes to survival.