Rock climbing leaves impacts on vegetation, but climbing is not exclusively harmful. Also, there are many simple ways to reduce your impact outside.

Computed tomography (CT) has been an incredibly useful tool for medicine - just recently has it become refined and efficient enough to work on small, soft-bodied invertebrates.

A bit on terrestrial leech evolution. Blood-feeding leeches living on land are a thing. There is more than on family, and they aren't each others closest relatives!

Evolutionary trees seem intuitive, but unfortunately they are not.