Bio 113 Portfolio
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  • Prion
    • Life Cycles
    • Evolutionary History
    • Kuru
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  • Virus
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  • Bacteria
    • Life Cycles
    • Evolutionary History
    • Pseudomonas syringae
    • Borrelia burgdorferi
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  • Archaea
    • Life Cycles
    • Evolutionary History
    • Sulpholobus acidocaldarius
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  • Protista
    • Life Cycles
    • Evolutionary History
    • Giardia lamblia
    • Phytophthora infestans
    • Hexacontium enthacanthum
    • Corallina officinalis
    • Discostelium discoideum
    • Sources
  • Plantae
    • Life Cycles
    • Evolutionary History
    • Dicranum polysetum
    • Adiantum aleuticum
    • Ginkgo biloba
    • Pyrus communis
    • Magnolia virginiana
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  • Fungi
    • Life Cycles
    • Evolutionary History
    • Lentinula edodes
    • Neurospora crassa
    • Gigaspora gigantea
    • Rhizopus stolonifer
    • Batrachochytrium dendrobatidis
    • Sources
  • Animalia
    • Life Cycles
    • Evolutionary History
    • Euplectella aspergillum
    • Lingula anatina
    • Priapulus caudatus
    • Mellita quinquiesperforata
    • Tachyglossus aculeatus
    • Sources

Evolutionary History

The earliest evolutionary history of plants on land appears in the early Ordovician period, about 475 million years ago; paleobotanists suspect that plants existed during the Cambrian period, 500 million years ago (21)

Green Algae (Charophyte)
(22)

Main Events of Plant Evolution (20):
  • Plants evolved from Green Algae; from a group called the Charophytes
  • It is believed that ancestral Charophytes lived in shallow water that often dried up
       -Natural Selection would have favored waxy cuticles and layers of tissue surrounding embryos to protect plants from             drying out
  • These pre-adaptations paved the way for the transition onto land
  • In order to move onto land, early plant ancestors had to change their mode of reproduction to suit life on land
       -gametes became contained within gametangia
       -the egg became fertilized within a female gametangium
  • Keeping the embryo contained is a fundamental difference between algae and plants
  • Early land plants had no competition with other plants nor were they preyed upon by herbivores
       -therefore, natural selection quickly dictated the expansive diversification of plants
  • The first land plants lacked vascular tissue (like modern mosses) so they were limited in ability and size
  • Root and shoot development and specialization quickly followed and this required the development of a vascular system
  • Early vascular plants had begun to diversify by 400 mya
  • In the Carboniferous period, large ferns and other seedless plants dominated the Earth
  • Next came the transition from homospory to heterospory; since homosporous plants required water for fertilization, they were limited to damp areas or environments; heterospory allows plants to expand to different environments (not dependent on water)
  • Heterospory led to the development of the seed which gave the new evolving plants more freedom since they now had a protected embryo capable of mobility and dormancy
  • Among seed plants, some developed flowers and fruits which furthered the survival and success rate of the seed to propagate the new plant generations
  • These plants, angiosperms, now represent over 235,000 species versus gymnosperms which only include 700 species
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