paleontology 4: The rise of seed plants and forests (v1.0)

I had talked about a major evolution of the rise of vascular plants earlier. This essay completes the discussion on plant evolution.   

Vascular plants developed robust root systems and gained greater height, likely to get more sunlight. These taller trees with foliage created more shade. Shade has an evolutionary advantage to other life. The combination of larger taller plants and high density gave rise to carboniferous forests. A major evolution change is the rise of global carboniferous forests. During the Carboniferous period, which took place from about 359 to 299 million years ago (across the Mississippian and Pennsylvanian sub periods of the carboniferous period), the dense and swampy forests were characteristic of the period. These forests gave rise to large deposits of peat, which over time transformed into rich coal stores in Western Europe, and North America and parts of Asia in regions that were lush tropically located regions during that Carboniferous period. The coal was produced by bark-bearing trees that grew in vast lowland swamp forests. These seedless plants were divided into two groups: bryophytes and vascular plants. Bryophytes are nonvascular plants that include mosses, liverworts, and hornworts. The vascular plants include club mosses, horsetails, ferns, and whisk ferns.  The growth of these forests removed huge amounts of carbon dioxide from the atmosphere, leading to a surplus of oxygen. Atmospheric oxygen peaked at 35% compared to 20% today. That coal has been used since the industrial revolution to generate energy. 

The evolution of non-flowering seeded plants (gymnosperms) is a great example of plants adapting to changes to environmental conditions. Heterosporous seedless plants are seen as the evolutionary forerunners of seed plants. The rise of non-flowering seed plants (gymnosperms) is a major evolutionary transition. Seed plants had a big impact on ecosystems. Seed plants create two types of spores – male and female, usually in a male cone and a female cone. Pollen (male) and seed (female) were innovative structures that allowed seed plants to break their dependence on water for reproduction and development of the embryo, and to conquer dry land.  Seeds and pollen—two critical adaptations to drought, and to reproduction that doesn’t require water—distinguish seed plants from other (seedless) vascular plants. Pollen can travel far from their original source, spreading the plant’s genes. The seed offers the embryo protection, nourishment, and a mechanism to maintain dormancy for tens or even thousands of years, ensuring germination can occur when growth conditions are optimal. Seeds therefore allow plants to disperse to the next generation through both space and time.  The first reliable record of seed plants is 319 million years ago in the Pennsylvanian subperiod of the carboniferous period (323 million to 298 million years ago). Seed plants dominated the landscape in the Triassic (252 million to 201 million years ago) and Jurassic (201 million to 145 million years ago) periods. An example of gymnosperms today are conifers. 

Flowering plants (angiosperms) and animals that pollinate these plants coevolved and was a major evolutionary transition. 80% of our land plants today use this approach using insects, birds or even mammals to pollinate. It was an extraordinarily successful evolution. 369,000 species of flowering plants are known which is 94% of vascular plants. Flowering plants first emerged about 130 million years ago (Cretaceous period from 145 million years to 66 million years). They were quickly followed by the origin and explosive diversification of animal pollinators. The study of plants is called botany. The study of flowers is called Anthology.