What did episodes 4-7 of "The Pulse of the Earth" say?

Pulse of the Earth is a TV documentary produced by the BBC.

The fourth episode Cave

Mysterious and unusual things in caves are usually overlooked. In fact, there are also some strange wild animals living there: cave angel fish hang themselves on the wall behind the cave waterfall through tiny hooks on flat fins; Jin Siyan caves are navigated by sonar system, and it is amazing how they have lived in this secret world full of stalactites, stalagmites and cave creatures for a long time.

The fifth episode Desert

About 30% of the land surface is desert. Although these areas are seriously short of water, the ecosystems are extremely diverse. Uncover the secret of survival in desert areas and experience the transient nature in this dynamic system.

Episode 6 Frozen World

The earth will continue its amazing and pleasant journey. We will follow the camera to make an impressive trip to Antarctica and arctic blue in the most extreme season. The timing camera will carefully observe a group of emperor penguins and show us the dynamic principles contained in their behavior.

Episode 7 Grassland

The film crew aimed at the frightened Mongolian gazelle, but few people actually witnessed their seasonal migration. At the same time, you won't miss the strange-looking Tibetan fox that first appeared in the camera. For six weeks, the staff used night vision goggles to observe the melee at close range in order to track a group of lions trying to kill elephants.