The Week 2 Ecosystem page lists all biomes extant in Week 2 and which organisms are present in each.
At the beginning of Week 2, most environments were completely barren of life except for East Darwin Temperate Coast and some deeper parts of LadyM Ocean. However, by the end, nearly every marine habitat was occupied, flora was present on all continents, and some small fauna had begun to establish themselves on land.
OceansThe oceans were bustling with life by the end of the week. Most large fauna were Geletaventrians and Binucleid Worms. Schools of Cish, especially Epidevoratoridae, often filled the oceans and provided abundant food for predatory fauna. Also present throughout the oceans were Nautstars, which are shelled filter-feeding Asterzoa somewhat analogous to ammonites. Oceanic mesofauna included various Knightworms and primitive Asterzoa, and arguably Shevs and Litusfoi as well. Astergnathids were also present, with one branch, the Roufos, sometimes filling somewhat significant predatory niches.
The benthic zone, especially along coasts, was home to countless crystal flora such as Sea Rupees, Petrolignopsids, Colony Crystals, Caltrops, Krelp, and Mosshrooms. Violet Flora also had a presence surrounding Wright, and Rooted Leafstars were a global phenomenon. Major reef-builders of this time were Wormreef and Reefstar. All this was eaten by various herbivorous fauna, such as Knightworms, Shovelfaces, and Grazestars, which in turn were also eaten by predatory fauna such as larger Knightworms, Astergnathids, and Siluros.
Most inhabitants of land by the end of Week 2 were flora, with a few exceptions.
GlickerOn the continental grouping of Glicker, the largest flora which filled tree- and shrub-like niches were Petrolignopsids. In Hydro in particular, Petrolignopsids were the only flora present aside from beach-dwelling flora such as the Tidal Leafstar. Aside from in Hydro, other flora present included Purple Flora, Peridots, and Rubyshrooms. Terrestrial fauna were relatively new by the end of the week, mainly consisting of Arthrotheres, including the ancestors of Arthrofelids and Tauroks, and small Knightworms with Mycostrum symbiotes.
WrightWright was populated far more slowly than Glicker, mainly becoming home to terrestrial branches of the Wormstem lineage. However, by the end of the week, it was also home to Asterplents, which were able to spread far and wide thanks to their airborne larvae, and Violet Flora, which crept in far more slowly from the beaches. Land fauna also included terrestrial Stickerstars, such as the Plenteater, and the rivers were also populated with more Violet Flora, Stickers, and even one species of Cish. Meanwhile, the frigid rivers of the far north also saw a rising population of Teal Flora. The nearby Yokto Island also began to be populated by Stemleaves, a branch of Asterfolia closely related to the Asterplent of the mainland.
A coronal mass ejection wiped out vast swaths of Sagan 4's life. Lifeforms closer to the surface were more likely to go extinct, while species with adaptations for radiation tolerance were more likely to survive. This favored Binucleida due to having a spare nucleus.
These were the only survivors:
Week 2 began with life clustered around the East Darwin Temperate Coast and in the LadyM Ocean.
Map of Week 2