Biomes
Forest, grassland, reef, ice and city — each biome writes a different body plan and calendar.
Habitat is the shared problem every species solves differently — find food, mates and cover inside a climate envelope that is already moving.
Migration
Flyways, spawning runs and seasonal ranges turn a map into a timetable.
Keystone roles
Some species reshape rivers, forests or reefs; remove them and the biome rewrites itself.
Human overlap
Farms, ports, temples and suburbs sit inside the same envelopes as nests and dens.
Climate envelopes
Temperature, ice and rainfall bands are moving; ranges follow or fragment.