Can you teach me how should I answer these questions please..

Why the events are significant?

First mammals:
First primates:
First modern humans:

2 answers

Also, there are more questions and I've done these.

First fish: fish did brief visits to the land and eventually they evolve into amphibians.

First land plants: plants were the first living things to move into land.

First amphibians: Amphibians only had to be in water to breed. Amphibians later evolved into insects which didn’t need to go into the water.

First reptiles: Reptiles evolved from insects and solved both main problems found in land. They lay eggs with dry shells and had skeletons rather than outer shells.
Some of the first mammals evolved into primates.
Some of the primates evolved into humans.