1 / 22

CENOZOIC LIFE

CENOZOIC LIFE. The CENOZOIC = “The Age of Mammals".

lashawn
Download Presentation

CENOZOIC LIFE

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. CENOZOIC LIFE The CENOZOIC = “The Age of Mammals". The original mammals evolved from reptiles. These small, insect eating, shrew-like creatures, had the advantage of being endothermic - they produced their own heat internally by consuming great amounts of food. This gave them the advantage of being active at night, when reptiles couldn't compete because of the cold. This enabled the mammals to become dominant at the end of the Mesozoic, when the climates got colder and many of the larger reptiles died out. Harry Williams, Historical Geology

  2. Another mammalian feature related to heat was the development of body hair, to help conserve the heat generated internally. Unlike reptiles, mammals also NURTURE their young using milk. Again, this helped to keep the young warm and ensured rapid growth in the vulnerable early stages of life. So, mammals had good survival skills. Harry Williams, Historical Geology

  3. Animals that are transitional between the reptiles and true mammals are still around today - the duck-billed platypus and the anteater are endothernmic, have hair, nurture their young with milk, but they both lay eggs (MONOTREMES). Harry Williams, Historical Geology

  4. The problem of keeping the young warm resulted in other adaptations, for example the MARSUPIALS (kangeroos, wombats, wallabies, opossums) - which nurture their young in a pouch; and the PLACENTAL MAMMALS - which carry the young inside the body for a longer period of development, feeding them nutrients from a placenta. Harry Williams, Historical Geology

  5. Apart from evolutionary changes designed to keep mammals warm; other changes also occurred which were adaptations to the changing environment. Perhaps the most important of these changes was the appearance of GRASSES and vast PRAIRIES in the Miocene. This led to the evolution of hoofed mammals - the UNGULATES. Harry Williams, Historical Geology

  6. One group of ungulates - the ruminants - are characterized by continuously-growing cheek teeth for chewing grass and multi-chambered stomachs for digesting tough grass. Due to the lack of cover on the open prairies, ungulates also developed speed or size to counter predators - long legs for running and running on toes, which became HOOVES. The ungulates are classified according to the number of toes; PERISSODACTYLS = odd-toed (if middle toe carried weight-> single hoof). Examples: zebra, horse, rhino, tapir. Harry Williams, Historical Geology

  7. ARTIODACTYLS = even-toed (if middle 2 toes carried weight -> cloven hoof). Examples: bison, pig, deer, hippo. Harry Williams, Historical Geology

  8. Other important orders included the carnivorous predators that preyed on the grazing mammals - ORDER CARNIVORA. Examples: Smilodon (extinct), dogs, raccoons, bears. Harry Williams, Historical Geology

  9. and the mammals with trunks, forerunners of the modern elephant -ORDER PROBOSCIDEA. Examples: mastodons (extinct), mammoths (extinct), elephants. Harry Williams, Historical Geology

  10. Particularly important, of course, was the evolution of the order PRIMATES, distinguished by stereoscopic vision and grasping hands - both of which probably evolved to facilitate a life in the trees. The primates evolved into the Late Cenozoic ancestors of Homo sapiens, who appeared in the Pleistocene (more next class). HISTORICAL GEOLOGY CLASS 2018 Harry Williams, Historical Geology

  11. The following slides show the transition from the early to late Cenozoic. Changes in environmental conditions included: cooler and drier climate; decline of woodlands; expansion of grasslands; decline in browsers, increase in grazers; evolutionary changes in mammals to adopt to vast open prairies (mainly related to running speed and a grass diet). Harry Williams, Historical Geology

  12. Harry Williams, Historical Geology

  13. Harry Williams, Historical Geology

  14. Harry Williams, Historical Geology

  15. Harry Williams, Historical Geology

  16. Harry Williams, Historical Geology

  17. MIDDLE EOCENE SCENE (~45 m.y.; primitive ungulates, mainly browsers, still lots of forest) Harry Williams, Historical Geology

  18. Earlier: Browsing teeth for crushing leaves, fruit, nuts, branches etc.. (mastodon) Later: Grazing teeth for grinding grass (mammoth) Harry Williams, Historical Geology

  19. LATE EOCENE SCENE (~35 m.y.; more open grassy land – more long-legged grazers) Harry Williams, Historical Geology

  20. EARLY MIOCENE SCENE (~20 m.y.; cooler drier climate; more advanced ungulates) Harry Williams, Historical Geology

  21. EARLY PLIOCENE SCENE (~4 m.y.; prairies – woods restricted to bottom lands near rivers) Harry Williams, Historical Geology

  22. LATE PLEISTOCENE SCENE (~15,000; predominately grazers) Harry Williams, Historical Geology

More Related