Discussing the differences between the physical environment of Antarctica to the Amazon rainforest or the Sahara desert is not a good comparison as these are “polar opposite” (no pun intended) in terms of physical geography. Also, focus on physical geography address the characteristics.
Also, speaking of which, you must consider scale. Antarctica, the Amazon, or the Sahara are simply way too large to compare and contrast, you must compare places that are small enough that can be pinpointed on a map. It is best to use specific cities, counties or national parks. Some individual countries which are small enough, say no more than 100 miles across in any direction might be ok to compare and contrast, otherwise focus on a single region/state/province,