Page 23 - The Dinosaur Book and Other Wonders of the Prehistoric World (DK-Smithsonian)

New species
Wing feathers ❯ The fossils of
Archaeopteryx preserve traces
of feathers that are very
similar to those of modern
birds. But the fossils also show
that it had the teeth and bones
of a theropod dinosaur.
Archaeopteryx fossil
Mass extinctions ORDOVICIAN (440 MYA)
Sometimes a catastrophic Up to 60 percent of marine species
event changes the world perished in a mass extinction at the
so radically that very few end of the Ordovician Period. especially in shallow coastal seas. wiped out all life on Earth.
animals can survive it.
This is called a mass
extinction. Since life
began, there have been
five major mass extinctions.
Each one wiped out much
of the life on Earth at the
time, allowing new species
to evolve and take over.
US_020-021_Evolution_and_Extinction.indd
If birds fly to a new habitat, such as an oceanic island, they may face
difficulties in finding food. Those that survive will be the ones that, by some
stroke of luck, have features that help them cope with the new conditions.
If they manage to breed, their young will tend to inherit these features.
Over many generations, this may give rise to an island form that is clearly
different from its mainland ancestors. This process creates new species.
The ancestor had
a thick beak for
cracking seeds. This finch uses
its hooked beak
to slice through Evolution and extinction
fruit and buds.
A probing beak is
ideal for pulling
seeds from flowers.
A beak with an
overbite is perfect
for digging up grubs.
A pointed beak helps
this finch to peck Galápagos finches
insects off leaves. The Galápagos Islands in the Pacific Ocean are
home to several species of finch, each with a
beak specialized for a different type of food.
A tool-holding beak enables It is clear that they all evolved from the same
this finch to use a twig to dig ancestor, which probably arrived from nearby
out prey from bark. South America.
Lost ancestors
The processes of evolution and
extinction cause a relentless turnover
of species, with new ones evolving as
others die out. This means that, over
the past 500 million years, more than
90 percent of all species on Earth
have vanished. We only know about
these life forms because their remains
have survived as fossils.
Trilobites don’t exist today—they
flourished in ancient seas about
500 years ago.
Trilobite fossil
DEVONIAN (358 MYA) PERMIAN (250 MYA)
The Late Devonian extinction The Permian Period ended with
mainly affected oceanic life, a global catastrophe that almost
60% 75% 96%
TRIASSIC (200 MYA) CRETACEOUS (66 MYA)
Many of the animals that coexisted This mass extinction destroyed the
pterosaurs, giant dinosaurs, and
with early dinosaurs died out at the most of the marine reptiles.
end of the Triassic Period.
70% 75%
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