В описании круговорота веществ иногда выделяют восходящую часть и нисходящую часть, Поясните, о чём идёт речь.

He does not know the Chinese language. And I do too.
I've seen this film.I it too.
We're going to buy a tent. And they are too.
I do not like this book. And she, too.
Lena did not work yesterday. Masha too.