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Beauty,Spring 2005
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The Narrative of Evolution

Rebecca Donatelli

"Now, here, you see, it takes all the running you can do to keep in the same place" (Carrol).

This line from Through the Looking Glass and What Alice Found There is now used to explain a certain evolutionary phenomena called coevolution. In the story Alice finds herself in a fantastical world and is following the Red Queen. The queen runs faster and faster and Alice runs faster and faster to catch up with her, however they both remain in the exact same place. Thus, the hypothesis that an organism must adapt as fast as it can just to keep from going extinct has come to be known as the Red Queen hypothesis. More specifically if one organism's survival is dependent on another organism it must adapt as quickly as that organism to stay alive and this is called coevolution.

There are over 250,000 species of angiosperms (flowering plants) which comprise about eighty percent of the plant population on earth. From experience one knows that many species of angiosperms are aesthetically beautiful due to their complex variations of form and color. In his essay Narrative Ronald Hoffman discusses how people generally find simple things the most pleasing. How is it then that the complexity and variation of angiosperms is still so beautiful? Hoffman's answer is that, "We construct with ease an aesthetic of the complicated, by adumbrating reasons and causes. We do so by structuring a narrative to make up for the lack of simplicity" (Hoffman 3-4). Narratives break down complexities into simpler parts or steps thus making the complexity more beautiful to the human mind. The complexity of the angiosperm group is beautiful because a narrative partly made up of the Red Queen hypothesis can be created that explains how these plants came to exist as we know them today.

Angiosperms like all animals evolved into their present form out of the need to pass their genes on to the next generation. An organism's evolutionary success depends on whether or not it is able to reproduce. This is so important that in some species parents actually die in mating or ensuring their offspring's survival. This fact is the foundation of evolutionary thought yet it is not at all beautiful because it is a gross oversimplification. This statement must be expanded to create a simple narrative that will in greater detail explain the evolution of angiosperms over time. In doing this the beauty of the complexity will be easier seen and understood.

To begin the narrative, the question of why organisms evolve at all should be addressed. Charles Darwin and Alfred Russell Wallace are credited for the theory of Natural Selection which explains this occurrence. The first tenet of this theory is that variations exist within a species and some of these variations are passed down from parent to offspring. For example in pea plants height is a characteristic that is determined by the genes of the parent plants. The second tenet is that more offspring are produced then survive to reproduce. Certain species of fish release thousands of eggs the majority of which are eaten by other organisms allowing only a very small percentage to reproduce and pass on their genes. Also, there may be more individuals in a population then there are resources to support and some individuals will die before getting to reproduce. Therefore there is a struggle for existence and reproduction. Certain individuals may have a variation that gives them an advantage over individuals who don't have that trait. They will survive to pass that trait on to their offspring and the others will die before they get a chance to. Therefore, it is possible for a population of individuals to evolve into an entirely new species over a long period of time (Dodson pp3-17).

There is a great deal of speculation as to what caused the earliest angiosperms to diverge from their predecessors which are the gymnosperms (conifers and ferns). However, it is known that both angiosperms and gymnosperms both share a common ancestor that was a single celled photosynthetic organism that lived in water. This ancestor had evolved the ability to create food by using energy from the sun in a process called photosynthesis. This adaptation gave the organism a competitive edge thus allowing it to reproduce passing the ability to photosynthesize to its offspring. The next major step for plants was terrestrialization or the movement of plants on to land. The individuals who had variations like roots that enabled them to live on land were able to tap into new resources that were unavailable to aquatic plants. This brings us to the evolution of gymnosperms which were the first plants to have seeds. These seeds had a soft covering that protected the egg which increased the chance of fertilization which is a great evolutionary advantage (Campbell).

That was a very brief narrative of an extremely complex series of events that took thousands of years but eventually lead to the evolution of angiosperms. Angiosperms diverge from gymnosperms in that they have a hard seed coat and the seed and other reproductive parts are found in a flower. The hard seed coat is an evolutionary advantage in that it protects the egg so that is why hard seed coats were selected for but the evolution of the many different forms of flowers has a much more complicated answer.

Ultimately flowers were evolved because like seeds they gave individuals a competitive advantage when reproducing. The intricate colors and structures of flowers expend a great deal of the plant's resources but the fact that angiosperms are the most diverse, successful plant group demonstrates that flowers are a wise investment. How do flowers create a reproductive advantage? Flowers have adapted mutualistic relationships with pollinators that are usually insects but can be small animals. In a mutualistic relationship both participants receive a benefit. Pollinators receive food in the form or nectar from the flowers and in turn put the pollen (a yellow powdery substance that is the male reproductive cell) in contact with an egg for fertilization. When the pollinator lands on the flower looking for food particles of pollen stick to it and when the pollinator moves on to feed at the next flower some of the pollen is deposited where it can then fertilize the egg. This makes it much more likely that fertilization would occur when compared to gymnosperms that just release their seeds and pollen into the air. This is evolutionary beneficial for the pollinators because they are provided with a source of food.

The relationship between angiosperms and their pollinators is a great example of coevolution. The relationships of these organisms have become so specific that they need each other for survival. This is where the Red Queen hypothesis comes into play. In these mutualistic relationships if one organism does not evolve as fast as the other it will go extinct because many of these relationships are so specific. Many times there is only one type of pollinator for one type of flower. This explains the diversity of color, form, and scent of flowers.

The shape and scent of a flower is used to attract pollinators. An example of a very specific relationship based on scent would be more commonly known as the corpse lily. This plant can be seven to twelve feet high and when in boom it releases a scent that smells like a rotting corpse. This attracts certain flies that come and spread the plant's pollen. The relationship between the hibiscus flower and the long beak of hummingbirds is a great example of co evolution. Hummingbirds have evolved long beaks because it has allowed them to reach deep into the hibiscus where other insects can't and eat the nectar. The form of the hibiscus has evolved such that its five stamens which have the pollen brush the head of the hummingbird as it eats the nectar (Koning). An example of an even more complex relationship would be common milkweed. The pollen in milkweed is not a powder but rather a waxy packet that is very sticky. The flower has horns and a slippery surface that makes it so that the insect can only land on the flower in a specific position where its legs go through these slits. In this position the packet gets stuck to the insect's legs almost like a saddle bag. When the insect goes to feed at the next flower it must again puts its legs through the slits and the packet of pollen breaks off and fertilizes the flower (Tikiela).
These are just three short stories in the narrative of how angiosperms have become one of the most diverse groups of organism on the earth. The narrative of evolution is what allows one to see the beauty of the variations of angiosperms despite the complexity.

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