The Tree of Life
The 4.6 billion years of earth's history is divided into three
, which are further divided into
There have been several episodes of
, but they were replaced by forms that evolved from the survivors; the trend has been an
of diversity over time.
was the most
and claimed over 90% of marine species. The
is famous for the
were Earth’s sole inhabitants from 3.5 to about
billion years ago. The oldest known
allowing the evolution of
organisms to obtain energy through
The first eukaryotes probably evolved from the
of small prokaryotes living within larger host cells and developing into
such as mitochondria and chloroplasts.
Multicellular eukaryotes diversified in the late Proterozoic eon, after
started to thaw.
The first multicellular organisms were
Most of the major animal
, appeared during the early
period in what is known as the
first colonized land during the
period in the
, followed by
Humans evolved from
epoch. If the
of Earth’s history were scaled to represent an
humans appeared about one
of the Earth's
has great impact on the habitats in which organisms
and shaped the diversity of life on Earth.