g07.    How did plate tectonics affect the diversity of ecosystems?

Pangea provided an ease of migration and global interactions.  At the time, global biological diversity was relatively low. When there is a supercontinent, there tend to be extremes in climate, elimination of habitat, regression of inland seas, and loss of barriers to migration. The more fragmented the landmasses, the more likely there is to be an increase in global diversity. Fragmentation episodes are accompanied by changes in sea level, perhaps as much as 650 meters lower, resulting in vast inland seas, which allow for the proliferation of marine invertebrates. Transgression of the seas would also moderate the temperature, creating better conditions for the increase in numbers of families. Small changes of floral and faunal elements at lower levels on the food pyramid would have profound affects on higher organisms, even on a global level. (See Figure 04: Food Energy Pyramid)

In the Cambrian through Ordovician, the supercontinent divided, making it more difficult for species interaction, and making it more likely that speciation would occur. From the Silurian through Devonian, the Ancient Caledonian Mountains formed (because of two plates coming together), putting up a barrier to migration and species interactions.  Land vegetation appeared in the Silurian with the advent of primitive vascular plants called psilopods. Plant species expanded rapidly.  True ferns grew in profusion.  Seed ferns began their colonization.

In the Pennsylvanian through Permian, the Ancient Hercynian Mountains formed, drawing the continents together, and allowing interactions of plants, insects, but eventually leading to more homogeneous speciation. Conifers and ginkos appeared. Glossopteris developed in the southern hemisphere.

During the Permian through Triassic, the continents merged once more, and a still more homogeneous ecosystem developed. During most of the 200 million years of the Age of Reptiles dispersal was a relatively simple matter. The Age of Reptiles produced only 20 reptilian orders.

Late Triassic through Jurassic found the continents again beginning to divide.  Barriers to migration and interbreeding occurred, allowing for the increase in the number of families of organisms. The trend toward divergence of continents continued through the Cretaceous into the Cenozoic, with more and more ecosystems emerging.

Cenozoic separations of the continents became extreme, causing evolution to occur in relative isolation. Isolationism caused the greatest diversity of species the world had ever hosted. The Age of Mammals gave rise to 30 orders of mammals in 65 million years.

e01.    What is biodiversity?

e02.   Where is life found in the water?

e08.    What are bioregions and biosphere reserves?

e11.    What types of old-growth forests are there?

e15.    What was early life like?

e17.    How do organisms use matter?

m11.    What is the aesthetic and recreational importance of organisms?

m12.    Why are organisms becoming extinct?

m13.    What are endangered and threatened species?

m16.    How are forests of commercial importance?

m78.    How do droughts and floods impact populations?