They swam faster and learned to hide
The right answer is Lichen.
In ecology, a pioneer species is one of the first forms of life that colonize or recolonize a given ecological area.
Lichens are composite organisms resulting from a symbiosis between at least one heterotrophic fungus called mycobionte, representing 90% of all, and microscopic cells with chlorophyll (green algae or cyanobacteria autotrophic for carbon) called "photobionts" .
