Wednesday, April 7, 2010
Revenge of the Ignored!
Throughout his book, Jerry Coyne provides evidence of evolution in bacteria, plants, and animals, but largely, if not completely, leaves out evidence of evolution in archaeans, protists, and fungi. Archaeans may even be the best example for natural selection, living in several different types of environments that are lethal to almost any other organism on the face of the planet. What kind of evidence for natural selection occurs in archaeans? In fungi? Protists? Why might Jerry Coyne have seemingly ignored these three kingdoms, considering that they are both so well-adapted to the environments in which they live? How might these kingdoms be utilized in an argument for evolution?
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Not that the book is lacking information, the book was written to inform the reader of logical arguments for the existence of evolution. The particular diction used is not overly scientific and all terms are defined by Coyne. To make a convincing argument, it is necessary for the topic to be relatable to the reader. The use of animals, plants, and bacteria is a more familiar topic to the general reader; therefore, there is a greater chance that using these as examples could help the reader understand the impact of natural selection. The average educated person does not contain the same basic knowledge for archaeans, protists, and fungi as compared to their knowledge of animals, plants and bacteria. Using the less known kingdoms could have resulted in confusion for the reader and brought them away from the main argument due to this confusion.
ReplyDeleteHowever, if Jerry Coyne were to have used them in his argument, they could have better examples of how adaptations over generations have allowed the species to survive in their environment. Fungi, in particular, have adapted their anatomy to maximize the efficiency at which they can draw nutrients from their surrounding environments. Such adaptations include the hyphae, which can penetrate through soil and tissue to expand the area the fungus is absorbing from, and sticky knobs which trap and degrade organisms. Likewise, fungi have also adapted methods of spreading their spores by the use of animals. This is a clear example of an adaptation of fungi because the earliest fungi fossils date back 1,500 million years while the earliest animal fossils only date back approximately 550 million years ago. Fungi adapted to utilize the mobility of animals to reduce competition among the next generation of fungi. Protists also have adapted in order to survive. On the surface, this is most easily seen by the massive diversity of the kingdom; they can be found in nearly every aquatic environment. The huge diversity could have been used as proof to support the ability of species to diverge through mutations. And as Mark mentioned in the question, specifically archaens could be a huge asset to the argument of evolution. Known as extremophiles, they live in unique environments which would normally kill other organisms such as unususally high temperatures and salinity. In occupying a unique niche, they have less competition from other unicellular organisms. Reduced competition increases their odds of survival and reproduction. All of these kingdoms would add to Coyne’s argument for evolution, but they would have also required outside knowledge of the kingdom for the reader to understand.
http://tolweb.org/Fungi
http://cas.bellarmine.edu/tietjen/Ecology/early_animal_evolution.htm
http://en.wikipedia.org/wiki/Evolution_of_fungi
http://courses.missouristate.edu/AlexanderWait/notes/Lecture%20Notes/Lecture%204.htm
http://en.wikipedia.org/wiki/Archaea
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ReplyDeleteLike what Jacob mentions, Coyne most likely chose animals as his main subject to describe the mechanisms for evolution because animals are more accessible to humans; furthermore, with respect to all the kingdoms, Kingdom Animalia is the most diverse and researched by other scientists for the basis of evolution.
ReplyDeleteNatural selection is corroborated by the evidence found linking the genetic origins of both archaeans and eukaryotes. Several pieces of DNA code are shared by both groups; furthermore, the fusion and bacteria and archaea results in a ring that leads to the eukaryotic branch (source: http://www.epjournal.net/filestore/EP06161163.pdf). This goes along with the idea in Campbell’s textbook of endosymbiosis in eukaryotic evolution (pg 576); the DNA of plastid genes in red and green algae closely resembles the DNA of cyanobacteria; this gives rise to the idea of secondary endosymbiosis where red and green algae were ingested in the food vacuole of heterotrophic eukaryotes. (protist evolution)
For archaeans, Jacob covered the main points regarding the extremophiles (halophiles, thermophiles); for example, the proteins and cell wall of the Halobacterium have unusual features that improve function in salty environments; the DNA and proteins of those archaeans that live in extremely high temperatures are also adapted; the Geogemma barossii (“strain 121”) is able to double its cell numbers at 121 C. Methanogens, another type of archaean, are adapted to survive only in anaerobic conditions.
For fungi, apart from adaptations in their anatomy like Jacob mentioned, have common homologous structures shared with plants and protists: the existence of nuclei and condensation of DNA with help of histones and the presence of actin and tubuline (for amoeboid movements of cells). Because plants and fungi have similar developments (cell wall, sessile, etc) but plants are autotrophic and fungi are heterotrophic; this shows that at an evolutionary perspective, natural selection favored fungi transitioning into a species that help recycle the decomposed material and waste. Furthermore, evidence of selection can be seen in the protection against drying out (plants – vascular system and fungi – spores that Jacob mentioned) and the evolution of lichens and mycorrhiza. (source: http://webcache.googleusercontent.com/search?q=cache:fR2PohT6q7YJ:www.biologie.uni-hamburg.de/b-online/e33/33.htm+evolution+in+fungi+and+plants&cd=1&hl=en&ct=clnk&gl=us)
Sources:
Campbell textbook
Coyne book
www.chemistry24.com/biology/evolutionary-history.html
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ReplyDeleteI agree with Jacob in that Coyne used animals, plants and bacteria with the intention of writing a book that the common public could understand easily. Some people don't even know what an archaean or a protist is, so trying to explain the adaptive features of those organisms would only confuse the reader and make the book 'boring'; channels like history channel and discovery tend to simplify explanations for certain concepts so that people are able to relate and grasp a general concept. Coyne most likely viewed getting into details about the evolution of organisms people had never heard of as redundant and unnecessary. However, Coyne could have mentioned archaeans because they have developed many adaptations to fit their environment and that they are an entirely separate domain ("Time for a change"). Some believe that the common ancestor of archaea, bacteria and eukarya was a thermophile, which means that living in a cool environment required an adaptation and thus "organisms that live in cooler environments appeared later in the history of life on Earth" ("The origin and evolution of Archaea: a state of the art"). This means that there is evidence showing that natural selection allowed eukaryotes and bacteria to diverge from archaeans. However, the relationship between archaeans and other organisms is still unclear, and scientists are unsure where to put them with respect to other domains in the phylogenic tree. While the classification of what exactly qualifies as an archaean is still being changed, it is apparent that natural selection chose the traits that allowed archaeans to be extremophiles, thriving in areas with extreme temperature, salinity, or acidity (http://en.wikipedia.org/wiki/Archaea). Evidence for the natural selection that led to the evolution of archaeans includes the enzymes in these extremophiles that don’t denature in certain extreme conditions ("The hunt for living gold. The search for organisms in extreme environments yields useful enzymes for industry"). For example, a special DNA polymerase from the archaean Pyrococcus furiosus has allowed scientists to use the polymerase chain reaction for the rapid reproduction of a segment of DNA (Campbell 403). Another thing pointing to the natural selection and evolution of archaeans (separately from bacteria) is the production of antibiotics that act differently from bacterial antibiotics, such as those seen in Sulfolobus ("Halocins and sulfolobicins: the emerging story of archaeal protein and peptide antibiotics").
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