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Chapter 10

BIOLOGY 1M03 Chapter Notes - Chapter 10: Laurasia, Bipedalism, Paleoclimatology

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Jon Stone

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Chapter 10: From Tree Shrew to Ape
During the Permian and early Triassic periods, much of the world’s fauna was
dominated by therapsids, a diverse group of reptiles that possessed traits such
as being warm-blooded and covered with hair that linked them to mammals that
evolved later
At the end of the Triassic, most therapsid groups disappeared and dinosaurs
radiated to fill all of the niches for large, terrestrial animals
One therapsid lineage evolved and diversified
These early mammals were probably mouse-sized, nocturnal creatures that fed
mainly on seeds and insects
They had internal fertilization, but still laid eggs
By the end of the Mesozoic era, placental and marsupial mammals that bore live
young had evolved
With extinction of dinosaurs at the beginning of the next era (Cenozoic) came the
radiation of mammals
According to Darwin’s theory, complex adaptations are assembled gradually,
each step favoured by natural selection
Modern humans have many complex adaptations, like grasping hands, bipedal
locomotion, toolmaking abilities, language and large-scale cooperation
Continental Drift and Climate Change
To understand the evolution of our species, it is important to understand the
geological, climatic and biological conditions under which these evolutionary
changes occurred
Evolution produces adaptation, but what is adaptive in one environment may not
be adaptive in another environment
oIf the environment remained the same over the course of human
evolution, then the kinds of evolutionary changes observed in the hominin
fossil record would have to be seen as steady improvements in perfection
of human adaptations
oBut if environment varied through time, evolution would have to track a
moving target
One factor that contributed to change in the world is the movement of continents
or continental drift
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