Answer:
1) The ecosystem would have the abiotic factors of low precipitation, dry winds, and low temperatures. The biotic factors would include the animals living with the penguins such as polar bears and yaks.
2) The population would suddenly increase if either the penguin's predators had a drop in numbers or if the penguin's food source became more readily available. This growth in population would result in food becoming harder to find and predators once again growing in numbers. This would eventually cause the penguin population to shrink once more.
3) Predators would die out. Whatever organism(s) were the penguin's food source would grow in size exponentially. Other animals may suffer a drop in numbers if the penguin's predators choose to prey on them.
The immune system, and the excretory system
(Honestly, all of them work to keep us 'healthy', but I believe these are the ones you're looking for)
