Week 4

The Week 4 Ecosystem page lists all biomes extant in Week 4 and which organisms are present in each.

Events
Week 4 opened with a mass extinction event caused by atmospheric oxygen and bioavailable nitrogen levels crashing. See the EBAD announcement for more information.

As in previous weeks, numerous species dispersed across flyways to islands and nearby coasts.

Generations

 * Generation 21
 * Generation 22
 * Generation 23
 * Generation 24
 * Generation 25