Land : , dry, batense ultraviolet radiation,lacking t makes movement in er comparatively effortless. to live onland, creatures o undergo s backbone too o support it. to survive out of er, marinecreatures needed to come up ernal arcecture—not t ofadjustment t . Above all and most obviously, any land creature o take its oxygen directly from ter it from er.

    t trivial co overcome. On tive to leave ter: it ting dangerous doinents into a single landmass, Pangaea, meant tline tal at. So competition tling neype of predator on tly designed forattack t it s emergence: tious time to find an alternative environment to er.

    Plants began tion about 450 million years ago, accompanied ofnecessity by tiny mites and ot to break doter on took a little longer to emerge, but by about 400million years ago turing out of ter, too. Popular illustrations o envision t venturesome land dious fiso puddle duringdroug, t visible mobile residents ondry land tle bugs (crustaceans, in fact) t are commonly toconfusion wurn a rock or log.

    For t learned to breatimes errestrial life first bloomed, o nearer 20 percent noo grow remarkablylarge remarkably quickly.

    And ists kno ingenious fieldknoope geocry. tiny plankton t iny protective son created tmosp s (carbon especially) to form durable compounds suce. It’s trick t goes on in (and is discussed elseo) term carbon cycle—a process t doesn’t make for terribly exciting narrative butis vital for creating a livable planet.

    Eventually