Unit 4: Mechanisms of Evolution
Animations
Study Guide
Chapter 25
The History of Life on Earth
Review
A major tool biologists use to study early life on earth is the fossil record buried in
layers
of
rock called
.
The 4.6 billion years of earth's history is divided into three
geologic
, which are further divided into
,
, and
.
Early photosynthetic
released
oxygen,
allowing the evolution of
.
The first eukaryotes probably evolved from
of prokaryotes within larger host cells and developing into
organelles
such as
and
.
Most of the major animal
phyla
appeared during the early
period in what is known as the
Explosion.
Mammals are
synapsids
that belong to the group of chordates called
.
The
movement
of the Earth's
due to
continental
has shaped the diversity of life on Earth.
Animation.
There have been several episodes of
mass
, but the extinct forms were replaced by others that evolved from the survivors; the trend has been an
of diversity over time.
The
(PT)
extinction
was the most severe, and claimed over 90% of marine species.
The
(KT)
extinction
is famous for the
disappearance
of
(except birds).
The extinction of the dinosaurs may have led to the
radiation of other species, such as
mammals,
which diversified to adapt to new
now made
available.
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