The modern biota evolved during the Cenozoic era.docx
University of Calgary
The modern biota evolved during the Cenozoic era
By early Cenozoic ear (65 mya), the positions of the continents resembled those of today.
Cenozoic was characterized by extensive radiation of mammals.
Flowering plants diversified extensively and came to dominate world forests, except in cool regions.
Mutations of two genes in one group of plants allowed them to use atmospheric nitrogen directly by forming symbioses
w/ a few species of nitrogen-fixing bacteria; dramatically increased the amount of nitrogen available for terrestrial plant
THE TERTIARY (65-1.8 MYA)
o Australia began its northward drift.
o Early in this era, it was hot and humid; the ranges of many plants shifted latitudinally.
o In the middle of this era, Earth’s climate became considerably drier and cooler.
o Many lineages of flowering plants evolved herbaceous forms; grasslands spread over much of Earth.
o Snakes and lizards underwent extensive radiations (birds and mammals too).
o Three waves of mammals dispersed from Asia to North America across the land bridge.
o Rodents, marsupials, primates, and hoofed mammals appeared in N. America for the first time.
THE QUATERNARY (1.8 MYA to PRESENT)
o Is subdivided into two epochs, the Pleistocene and the Holocene.
o The Pleistocene was a time of drastic cooling and climate fluctuations; 4 major and 20 minor “ice ages” cause
the spreading of massive glaciers across the continentsranges of the animals and plants shifted toward the
o Relatively few species became extinct during these climate fluctuations.
o Pleistocene was