Saturday, March 27, 2010

plant evolution

Most of the evidence Coyne uses in the book to prove evolution as true has to do with animals. For instance, evidence he uses deals with the fossils of animals, the embryos of animals, etc... to prove his point. How come Coyne didn't use more examples relating to plants in his book? On the other hand, how did he use plant examples in his book to prove evolution?
Also, Coyne says on pg 149 that features such as bright colors and ornaments in animals are molded by a type of sexual selection, mate choice. In plants, who can't choose mates, why did bright colors and ornaments evolve? Give specific examples of plants with bright colors/ornaments, and example why they adapted them.


  1. I believe that Coyne didn't use more examples relating to plants in his book so that he could keep his target audience's attention. Humans, whether they are collegiate scholars or high school students, would be able to identify more with animals than plants because we are animals. Therefore, we would be more able to understand the concepts behind evolution as they apply to animals more so than as they apply to plants. Coyne does, however, incorporate some examples of plants to prove evolution in his book. One such example was the use of artificial selection to produce plant diversity. He states that the ancestor of an ear of corn was a grass, the tomato can now be bred so that its weight increases, and that the wild cabbage gave rise to broccoli, domestic cabbage, kohlrabi, brussel sprouts, and cauliflower (127). Another example of plant evolution that Coyne uses is to describe the different types of cacti that appear in different deserts. He explains that "in North and South America, the succulents are members of the cactus family. But in the deserts of Asia, Australia, and Africa, there are no native cacti, and the succulents belong to a completely different family, the euphorbs" (91). He later says that these two plants look very alike but are fundamentally different because the habitats in which each lives differ in subtle but important ways (91). Like peacocks, plants, especially flowering angiosperms, come in a variety of shapes and colors. Bright colors serve as an evolutionary advantage for such flowers because bees and other animals that pollinate flowers are more attracted towards more brightly colored flowers, believing that such flowers have sweeter nectar, according to an article entitled "Plant and Animal Evolution" written by the staff at the University of Waikato. This enhances the flower's ability to reproduce because it "increases the odds of fertilization by ensuring that pollen is transferred efficiently from flower to flower." According to a gardening know-how article by Nikki Phipps, "flower color significance also depends on the specific pollinator. For instance, bees are attracted to bright blue and violet colors. Hummingbirds prefer red, pink, fuchsia, or purple flowers. Butterflies enjoy bright colors such as yellow, orange, pink, and red." One example of such a flower is the Dahlia coccinea, which has a pastel pink color with a bright orange-yellow center. There are at least 36 species of this genus - the Aztecs used to grow this flower for cultivating and decorative purposes, but today, the most common reason for planting these flowers are for gardening purposes. The success of this flower is mostly due to the high number of animal pollinators that are attracted to the Dahlia flower because of its showy colors. If you don't believe me, check out the Dahlia gallery and judge for yourself:

  2. First off, I believe Coyne didn’t use more examples relating to plants in his book because the proof that evolution and natural selection took place can be seen in the fossil record. Because animals have bones or bone-like structures, fossils remain millions of years later; on the other hand, plants do not have such structures so it is much rarer to find actual fossil evidence of a plant. In comparing plants to their ancestors and ancestral forms, most of the evidence is seen by evaluating the DNA sequences of current plants to determine if any common ancestors took place between them. Because this book is written for the general public and is “One of Newsweek’s Top Fifty Books to Read Now” (Back cover of book), it is easier for the general public to identify to similarities between bone structures as opposed to similarities in DNA sequences. We have all seen the T-Rex at the museum, but a very select few have actual seen a comparison of DNA between the Tiktaalik rosae and the alligator.

    Coyne, however, does mention plant examples in his book to prove evolution. He mentions that “flowers, vegetables, and so on – all came from humans choosing variants present in wild ancestors, or variants that arose by mutation during domestication” (127). Notice the last word in that quote: domestication. This may be another reason as to why Coyne chose not to mention plants as much as animals. Most of the plants the human being species identify with are the ones we eat. These plants have coevolved with humans and through human-sponsored natural selection, in which the human species would breed and handpick the biggest or tastiest plant, would lead to the evolution and formation of certain types of plants. For example, human beings would pick and replant the seeds for the biggest tomato with the hope that the end result would be larger tomatoes. “The ancestral tomato weighed only a few grams, but has now been bred into a two-pound behemoth…with a long shelf life” (127).

  3. Another reason why he may not have chosen to deal with plants as much as animals, which also goes along with the domestication, is that Coyne points out that evolution and natural selection is a very long process in which adaptations often take millions and millions of years to occur. On the contrary, however, “the domestication of all wild plants occurred within the last twelve thousand years” (127). This would thus undermine one of Coyne’s arguments. Creationists believe that macroevolution, in which one organism evolves to another, is impossible. Coyne describing that the process takes a very long time and that the changes that occur are very subtle heightens the credibility of his argument.

    Coevolution can be defined as the change of a biological object triggered by the change of a related object ( The question asks why bright colors and ornaments evolved on plants that don’t choose mates. The answer to this is coevolution. Plants have coevolved with bumblebees in order for both of them to survive and reproduce. Bees go to flowers to drink up their nectar, which bees with then use to create honey, a major energy source for them ( . During this process, the bee accidentally acquires pollen from the plant which it then transfers to other plants when it goes to gain nectar from other plants; this enables fertilization ensuring the survival and reproduction of the flowers and plants (

    One example of a plant that formed a flower with bright colors is the Night-blooming cereus ( Bees, who are yellow and black, are attracted to bright colors; specifically, bees are attracted to the color yellow as it resembles the color of honey. As a result the Night-blooming cereus formed a bright yellow center in the flower where the pollen and nectar are, which is engulfed in bright white petals. This evolved in order to attract bees to these specific flowers in order to out-compete competitor flowers; because of this Night-blooming cereus have been able to continually survive and reproduce.

  4. While Coyne does seem to ignore plants, they have an ample amount of evidence that evolution has occured. It is thought that land plants have evolved from green algae. Evidence for this include that they have similar chloroplasts with chlorophyll for photosynthesis. During photosynthesis the pigment, which for both green algae and many land plants is chlorophyll, is hit by a photon which reduces it causing the electron to leave the pigment, causing the pigment to be oxidized. This continues to occur until the reaction center is oxidized and the electron is passed to the primary electron acceptor. During non-cyclic photophosphorylation, light hits the pigment in Photosystem II and electrons jump to a higher energy level and then come back down, causing the release of heat energy to allow the next electron to jump, until it hits P680. The electron then goes to the primary electron acceptor where a water molecule is then split, causing P680 to be restored. The electron goes through an electron transport chain where ATP is produced and it then restores P700 after P700 was oxidized. Then, NADPH is produced. This complex process is then followed by the Calvin cycle. All in all, the similar pigments between the green algae and land plants cause them to both use photosynthesis as their energy source. Another similarity suggesting that land plants evolved from green algae is that they both have flagellated sperm. Why did this evolution occur? As the plants were removed from the water and migrated towards land they faced many challenges and they had to adapt in order to survive and reproduce. One major challenge was drying out. In order to prevent the plant from losign too much water, the plants began showing a cuticle, a waxy covering to protect the leaves. Also, guard cells became evident which help open and close stomata so that the plant can monitor its water loss on hot or cold days. To endure the large variation in temperature, some plants such as deciduous trees began to release their leaves in the fall. Other trees began forming needles, and some began releasing antifreeze chemicals in order to protect itself from the cold. In order to protect itself from herbivores an dparasites, plants formed thorns, or some even released toxins to make it difficult for organisms to eat. The plants experienced a lack of motility and were not able to stand up right. The adaptation from this problem was the formation of the apical meristem and lignin to help it stand upright. These are just a few of the many adaptations land plants had to undergo in order to survive out of the water. All of these examples show how natural selection led to the evolution from green algae to land plants. All in all, not only did plants develop brightly colored flowers to increase reproductive success, but they also were forced to adapt many other unique features in order to survive.