James Farley
Underwood
12/04/07
D5
Log 7: Chapter 8- The Making and the Evolution of Complexity
Synopsis:
(1) What are Microevolution and Macroevolution?
These two terms stem from debate in the scientific community as to whether or not evolution is valid or invalid. This argument polarizes when the discussion of complex structures comes into play. Evolution doesn’t presume or claim to know all of the answers but in the gray areas of argument, such as evolution of complex biological structures, the speculations of microevolution and macroevolution tend to arise. Microevolutionists accept that adaption and variation can occur within species. Macroevolutionists believe that those adaptive and variational changes can occur beyond the confines of the original species to eventually form new species. Both of these ideologies have been examined and studied thoroughly.
(2) What is "Evo Devo?"
It is widely believed by the scientific community that variational changes are caused by the development adjustments in a particular species. Evo Devo simply stands for evolution of development. By studying the cause of the effect, scientist gain invaluable insight into the conceptual understanding of evolution. In studying development, complex structures of organisms are often the foremost examination of alteration. When examining the evolution of complexity in species, one must be extremely observant in documenting all findings in order to draw conclusions pertaining to similarities, differences, and ultimately variations within evolution.
(3) Explain how discoveries about the Pax-6 gene shows that all complex eyes evolved not from scratch each time but from a common ancestor having a very primitive eye.
The Pax-6 protein is a protein which exists in fly, mouse and human proteins. The main arguments suggesting that this protein came from a common ancestor rather than independent mutation relies on the fact that there are a large number of species producing Pax-6 and that the production of this protein has remained unchanged for 500 million years. It is thus believed that the Pax-6 of the common ancestor was used to manufacture a primitive eye and that as time went on, the species then split from the common ancestor. This eye was believed to be composed of an optic nerve and photoreceptors. Since then, much hasn’t changed. Scientist use a variety of methods to ascertain answers to genetics’ deepest questions in order to better understand the vastness and diversity of life.
(4) Explain how studies of the ragworm show that the evolution of vertebrate eyes and other animal eyes were not independent events.
The marine ragworm, or Platynereis dumerilii, possesses a two-celled eye which is enough for it to survive in its habitat. Though these eyes may appear to be simple in form, they are extremely advanced in performance. The eyes of the ragworm function using light-sensitive opsin proteins found in much larger organisms. Ragworm and larger complex animals alike use opsin detect light. As stated by Carroll, “The inescapable explanation is that opsin existed in a primitive eye in the common ancestor of most animals, and has since been used for detecting light in all varieties of eyes” (Carroll 197). This example of similarity is a small illustration that shows that ragworm eyes and vertebrate eyes were not independent of one another.
(5) What's the difference between proteins that are responsible for physiology (like opsins, globins, ribonucleases, and odorant receptors) and those responsible for form (like the Pax-6) Use the phrase "tool kit" gene in your answer.
Proteins responsible for physiology deal with alterational changes of DNA that change within the confines of the organ the cell exists in. Proteins responsible for form have the ability to either produce or remove the organs in which physiological changes take place. For example a form mutation can cause the eye to become non-existent in the offspring of a species. A physiological mutation can only cause change in the protein opsin being manufactured for the ability of an organism to see different wavelengths of the spectrum. The tool-box of physiological changes coinciding within the form of the organ enables differences to occur within species. Therefore, form mutation affects existence of an organ and physiological mutation affects the variational changes operating within that organ.
(6) What is the role of regulatory DNA sequences on how the tool-kit gene Pitx1 produces the two types of stickleback fish pelvic skeletons? Make sure you explain just what regulatory DNA is and thus also explain its connection with genes that code for proteins.
There are two main types of stickleback fish which are still able to reproduce today. Pitx1 serves as “the major gene responsible for the reduction of the pelvic skeleton” (Carroll 206). DNA sequences serve as switches in the code that determine the usage of a gene. Tool-kit genes are the guideline basis for which variation within the organ is created. Based on the DNA in which the sequence chooses to activate or deactivate the switches of the tool kit genes, mutations will effect the location and functionality of these DNA sequences as well. Small changes as a result of mutation lead to large noticeable variational differences over time.
Some of the best data comes from living examples of today’s world. There is only so much that can be told from a fossil or something that lived long ago. By studying living organisms, both genetic and behavioral traits can be studied simultaneously. It is important for scientists and non-scientists alike to gain a conceptual understanding of that which is being studied in order to make real world applications in both personal and professional settings. Understanding how genes code for proteins in the stickleback fish helps humans understand how their own genetic coding process works and how it relates to living organisms in the world around them.
(7) Explain how one gene, the "paintbrush" gene, can create diversity in fruit-fly wing patterns (including a wing spot - how one evolves and how one disappears).
The fruit fly, or Drosophila melanogaster, contains many design patterns within its differences as a species overall. The fruit fly wings are colored using enzymes which process and break down melanin. The spots and dark areas of each wing are the evidence of black pigment built up. The mutations in each wing show a different design scheme and location for the pigment. These mutations are then passed on to the offspring. The offspring grow to adulthood and then have their own mutational variations. The cycle of mutation reoccurs over and over to form new and beautiful adaptive diversity.
Take Away Idea:
The most important concept I took away from this reading is understanding the concepts of micro and macro evolution. Adaption is studied closely by examining the development of evolution. Smalls changes in species result in larger changes over time. I also found it fascinating to look at the design of the fruit fly wings and how these designs were created and mutated through the “paintbrush gene”. Life is fascinating and The Making of the Fittest has sparked my interest in the field of genetic variation and the causes of adaption. I have learned many interesting and amazing things through Carroll’s findings. This is only the beginning.
Most Challenging Concepts:
Overall, the chapter was a very easy read. I had some trouble understanding the concept of tool-kit genes. I got the basic idea that Carroll was emphasizing in that tool-kit genes are responsible for variation within specific body parts and organs. I just thought the subject needed some clarification. The ideas of variation in eyes were fascinating. Nothing else in the chapter presented a problem conceptually.
A Seminar Question:
How diverse are human paintbrush genes as compared to paintbrush genes or other organisms?
Aesthetic Awareness:
This chapter was full of aesthetic awareness. Careful and detailed observation led to well supported scientific conclusions. The study of photoreceptors and opsins in a selection of different eyes allowed scientists to make the connection that different organisms sharing the Pax-6 protein shared a common ancestor. Observing the genetic differences in the reduced and full pelvis of the stickleback fish enabled scientists to find the Pitx1 gene which is responsible for the genetic shift between the two. Scientists were also able to determine the existence and functionality of paintbrush genes within organs and body parts by first looking at the visual evidence of adaption in the variational design of fruit fly wings. All of these scientific discoveries were spearheaded by aesthetic awareness of visual observation.
Today’s science relies on data and sheer scientific evidence. The initial quest to find scientific answers to genetic riddles starts with using aesthetic awareness to make detailed observations. These detailed observations can be used as a starting point for further scientific investigation. Aesthetic Awareness is important because it puts a face to science. Without the visual representation of what is being objectively and subjectively studied, science losses its appeal to the general public because they are not so adept to the matters of complex science and mathematics.
Critical Thinking:
This chapter was about making connections to different variables in order to further understand the world around us. Critical Thinking was used to focus research into the evolution of development of complex organs/body parts. At first glance, the fly, the mouse, and the human are all extremely different from one other. When studied further, science reveals that each share a protein responsible for the construction of the eye which is known as Pax-6. This conclusion would not have been discovered if Critical Thinking were not applied.
The ragworm may look like a primitive creature. However, as scientists chose to examine it past mere surface appearance, they discovered that the ragworm’s eye is complex and contains the opsins humans use to synthesize light. Critical thinking also spurred the human intuitive mind to discover the Pitx1 gene responsible for variation in the pelvis of the Stickleback fish. These and many other discoveries await human kind. With critical thinking, the possibilities are endless.
Connection:
When I read about the paintbrush
genes which are responsible for the diversity in fruit fly wings, I remembered
some of the observations I made at the
Vocabulary:
Cnidarians- kingdom classification for corals and sea anemones
Platynereis dumerilii- scientific name for marine ragworm
Drosophila melanogaster- scientific name for the fruit fly
Key Concepts:
Microevolution vs. macroevolution- divergence in scientific thought as to the confines of adaptation occurring within the parameters of a species or being able to adapt significantly as to create a new species over time
Evolution of development- instrumental study used to examine variation and adaption in complex organs/body parts
Role of paintbrush genes- paintbrush genes are responsible for genetic variation and diversity within specific organs/body parts
Bibliography
The Making of the Fittest: DNA and the Ultimate Forensic Record of Evolution by Sean Carroll, W.W. Norton; Reprint edition (September 10, 2007)