Answer:
The tropical rainforest.
Step-by-step explanation:
Oceania is a region that comprises the territories of Australia, New Zealand, New Guinea, and many island groups in the Pacific Ocean. Most of the islands in Oceania tend to have a very similar climate, with only Australia sticking out as having multiple different types of climates and ecosystems. The ecosystem that is the most abundant with plants and animals is the tropical rainforest.
Tree kangaroos, frogs, birds, ferns, and tall and dense trees, are typical for the tropical rainforest. This ecosystem can be found in the northeastern part of Australia and across New Guinea. This ecosystem can also be found in most of the island groups in Oceania, though they lack some of the organisms mentioned. The characteristics of the tropical rainforest are constantly high temperatures, high levels of precipitation and humidity, and very high biodiversity.