Before plants, the earth was a rather dull place. It is predicted that the plants changed land quite a lot. For example, before plants, rivers were thought to be broad, shallow, and laid down in wide, flat sheets. Then plants growing and roots spreading in these areas helped to transform the land into areas of mud with rivers in long continuous, and narrow channels. Bacteria started forming before plants, and it is believed that this bacteria is what began to pump oxygen into the atmosphere. About 2 billion years after bacteria started developing, was the rise of bryophytes descending from the green algae. This is believed to have happened about 409-354 million years ago. They lack lignified vascular tissue and therefore cannot grow to be very tall. Therefore it is believed that the bryophytes were very small and low to the ground. They also needed water to survive and were found most commonly in wet habitats. With the emergence of these basic plants, they were then able to provide more of a food source for early amphibians which evolved shortly after. Amphibians and insects evolved close in the same time-frame, along with early vascular land plants. The first vascular plants fossils appeared about 425 million years ago in rocks from middle Silurian. These plants had a few features that made them able to adapt well to life on land. First, the vascular systems abled them to transport water, nutrients and sugars much more efficiently. Also, they were able to synthesize lignin which made their cell walls very supportive. Therefore, these features abled them to grow larger and away from moist habitats. They include ferns, club mosses, horsetails, etc, and have true roots, stems, and leaves! One phylum of seedless vacular plants, progymnosperms, is believed to be what gymnsosperms evolved from about 380 million years ago. These are vascular plants with seeds. Gymnosperms were/are vascular with naked seeds. Many were (and are) large and tall trees, such as the conifers. The earliest had slender stems, sometimes branched, with leaves not borne close together, and then evolved to having leaves densely crowded together. The oldest TRUE gymnosperms, which produce seeds (not spores), first appeared about 365 million years ago. They also now had pollen grains to protect and transport male gametes and were therefore no longer dependent on water for fertilization. Many became well adapted to drier environments rather than being dependent on moist habitats like previous plants. By the late Paleozoic there came into existence more conifers, and then even more began to appear in the Mesozoic era. These had dense, compact wood and needlelike leaves. Reptiles evolved and then angiosperms were able to emerge. Last but not least is the emergence of angiosperms. Angiosperms first appeared in the fossil record about 130 million years ago. They are known as flowering plants since they possess flowers and they also have highly modified shoots that carry the male and female reproductive structures. Also, another feature that separates these from gymnosperms is the fact that their embryos are protected by an ovary wall which develops into a fruit after fertilization. They aren’t unprotected like the naked seeds and scales in the female cones. Along this timeframe, birds and mammals then evolved and they could feed and survive off of angiosperms. Angiosperms are still hugely important to birds and mammals (AND us humans) in present day. Approximately 54 percent of the food people eat is provided by grain (seed) from cultivated varieties of just three grasses: rice, wheat, and corn. Even meat we eat is provided because of these three things…cows wouldn’t survive without their plant food, and therefore wouldn’t grow big for us to be able to eat. Also corn, fruits, and vegetables are types of angiosperms, which proves how important they are to us today. Angiosperms have been so successful in modern times because of a few reasons. First, they are very developed and able to have double fertilization and produce asexually. Also, many have “protected” seeds, where the ovary grows and is protected by a fruit or covering. Lastly, they are able to grow very rapidly compared to other plants. In conclusion, evolution is the base and process of how things in present time have formed. Both animals and plants are believed to have evolved from eukaryotes in the sea. They owe their survival, environment, and feeding to each other, and continue to adapt and evolve in present-day.

Sources Cited Emms, Simon K.. (2002). Evolution of Plants. Retrieved Feb 20, 2014 from http://www.encyclopedia.com/doc/162-3400700159.html. Encyclopedia Britannica. (2014). Gymnosperm. Retrieved Feb 21, 2014 from http://www.britannica.com/EBchecked/topic/250316/gymnosper. Soltis, D. E., Bell, C. D., Kim, S. and Soltis, P. S. (2008). Origin and Early Evolution of Angiosperms. Annals of the New York Academy of Sciences. Retrieved from http://onlinelibrary.wiley.com/doi/10.1196/annals.1438.005/full Taggart, Ralph E. (2012). The First Vascular Land Plants. Michigan State University: Department of Plant Biology. Retrieved from http://taggart.glg.msu.edu/isb200/fland.htm.