Continental Drift Theory plant phytogeography pptx

Continental drift theory plant phytogeography seminar present by R Parihar

1. Continental drift theory Tracing Plant Evolution Across Shifting Continents

2. Contents Introduction to Continental Drift Theory The S upercontinent Pangea Botanical Evidence for Continental Drift E volutionary C onsequences of Continental D rift Theory References

3. Introduction to Continental Drift Theory Alfred Wegener was a German meteorologist and geophysicist who proposed the theory of continental drift in the book "The Origin of Continents and Oceans" in 1915. The Continental Drift Theory proposes that the Earth's continents were once joined together in a single landmass called Pangaea , which later broke apart around 200 million years ago and drifted to their current positions. Wegener supported his proposal with evidence from geology, paleontology, and climatology . His ideas were initially met with skepticism but laid the groundwork for modern plate tectonics theory. Plate tectonics provides the mechanism by which continents move. The movement of convection currents in the mantle drives the motion of these plates, causing them to collide, separate, or slide past each other. Pangea Plate tectonics

4. The supercontinent pangea Pangaea, meaning "all lands" in Greek, was a supercontinent that existed during the late Paleozoic and early Mesozoic eras , approximately 335-175 million years ago. Pangaea was a single landmass, surrounded by a vast ocean known as Panthalassa . Pangea was made up of two major landmasses: Laurasia: Located in the northern hemisphere, Laurasia was composed of the continents that now form North America, Europe, and Asia. Gondwana: Positioned in the southern hemisphere, Gondwana comprised the landmasses that currently constitute South America, Africa, Antarctica, Australia, the Indian subcontinent, and the Arabian Peninsula.

5. Botanical evidence for continental drift Fossil Distribution: Paleontologists have found identical fossilized plant species on continents that are now widely separated by oceans. For instance, fossils of the Glossopteris fern have been discovered in South America, Africa, India, Australia, and Antarctica. The presence of identical plant fossils across these continents suggests that they were once connected. Paleoclimatic Evidence: Some plant fossils indicate past climates that are incompatible with the present-day locations of the continents. For example, fossils of tropical plants have been discovered in regions that are currently too cold to support them. This suggests that these regions were once situated closer to the equator when the continents were joined. Fossils of  Glossopteris  (dark green) found in all of the southern continents provide strong evidence that the continents were once amalgamated into a supercontinent  Gondwana

6. Botanical evidence for continental drift Geological Distribution of Plant Species : The distribution of certain plant species across continents can be explained by continental drift. For example, the genus Nothofagus , commonly known as southern beech, is found in South America, Australia, New Zealand, and Antarctica . The presence of Nothofagus on these widely separated continents supports the idea that they were once connected. Matching Geological Features : Matching geological features, such as mountain ranges and rock formations, across continents further support the idea of continental drift. For example, Appalachian Mountains in North America share similar rock types and geological structures with the Caledonian Mountains in Europe Southern Hemisphere Maps and Present-Day Nothofagus Distribution The Scottish Highlands, the Appalachians, and the Atlas are the same mountain range, once connected as the Central Pangean Mountains

7. evolutionary consequences of continental drift theory Isolation and Speciation : As continents drift apart, populations of plants become isolated from each other. Over time, this isolation can lead to genetic divergence and ultimately speciation. For example: The separation of Gondwana into South America, Africa, Antarctica, Australia, and the Indian subcontinent led to the divergence of flora in these regions. One notable example is the Proteaceae family , which includes iconic plants like Proteas in South Africa and Banksias in Australia. These plants evolved separately due to continental drift and developed unique adaptations to their respective environments. Intercontinental Dispersal : Continental drift not only separates but also brings landmasses together, facilitating the dispersal of plant species across continents. For instance: During the Cenozoic era, the connection between North and South America via the Isthmus of Panama allowed for the exchange of flora between the two continents. This led to the Great American Interchange , where plants (as well as animals) migrated between North and South America. Examples include the spread of various tree species like oaks (Quercus) and palms (Arecaceae) between the continents. Worldwide distribution of Proteaceae Formation of isthmus of Panama due to continental drift

8. evolutionary consequences of continental drift theory Formation of New Habitats : Continental drift creates new habitats as landmasses move and climates change. This can lead to the evolution of new plant species adapted to these novel environments. For example: The separation of Antarctica from South America and Australia during the late Mesozoic and Cenozoic periods created the isolated polar environment of Antarctica. This isolation led to the evolution of unique Antarctic flora, including mosses, lichens , and hardy flowering plants like Antarctic pearlwort ( Colobanthus quitensis ). Colobanthus quitensis

9. References 1. Alfred Wegener’s Hypothesis on Continental Drift and Its Discussion in Petermanns Geographische Mitteilungen By Imre Josef Demhardt 2. The breakup history of Gondwana and its impact on pre-Cenozoic floristic provincialism By Stephen McLoughlin  3. Cretaceous to Paleogene Vegetation Transition in Antarctica By David J. Cantril

10. Thankyou!