Monthly Archives: August 2012

Nacirema

Language, or the way things are worded, can affect how a reader judges and views a culture.

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D.2a: Origin of Species: Microevolution

A gene pool all the genes in an interbreeding population at a certain time. Allele frequency is the frequency of an allele, as a proportion of all the alleles of of a gene, in a population.allele frequencies range from 0 to 1.0, or as a percentage
evolution always involves a change in allele frequency in a population’s gene pool, over a number of generations. Evolution involves a change in allele frequency in a population’s gene pool over a number of generations. This is expressed by the equation E = ∆af/t.

D.1c Origin of Life: Endosymbiosis

Endosymbiotic theory

Lynn Margulis is known for her theory on endosymbiosis. This theory states that chloroplasts and mitochondria were once free living organisms that lived in other organisms and gave up their independence. They have their own circular DNA and ribosomes that resemble the ribosomes of prokaryotes. Their size, shape and double membranes resemble those of other bacteria.

Thinking about science: the theory of endosymbiosis

1. Belief is when you think something is true but may not be able to prove it. Knowledge is when something has a lot of evidence to support the idea and such.

2. Margulis’ belief is falsifiable, however, it is still a belief and she uses words such as “I think”, which shows that there is not clear evidence to support it therefore, it cannot be a scientific claim.

D.1b Origin of Life: RNA world

Protobionts and the role of RNA

The packaging of abiotically produced molecules into structures with different internal chemistry from their surroundings would have been an important stage of the origin of cells. These are referred as protobionts. They exhibit properties such as the response to the environment, simple reproduction, and basic metabolism. A fourth requirement of the origin of life would be something that makes inheritance possible. In systems these days, enzymes are used for replication and catalysis and for these enzymes to be created, there must be genetic material. RNA is most likely the original molecule of inheritance as it can self-replicate and has catalytic properties as well as its variable sequence, allowing it to store information.

Oxygen

Early cells would have competed for energy sources and this would have provided the selection necessary for evolution of photosynthesis. The oxygen produced would have dissolved in the oceans or used in chemical reactions. It then began to be released in the atmosphere. Early prokaryotes have contributed to rises in atmospheric oxygen, although it is thought that the emergence of eukaryotes and chloroplasts were responsible for further rises. The rise in oxygen may have led to the extinction of certain groups of prokaryotes while other groups were better adapted to deal with oxygen, such as cellular respiration.

No Grades in School

What do you think would happen if there no grades in school- or if the IB diploma did not culminate with a series of tests and quantitative results- would you work less hard, harder, about the same? 

If there were no grades, tests, or results of any kind at school, I think that I would work less hard than I do now. This is because I work hard right now so that I can achieve good grades, and hope that those good grades will help me get into a good university. However if there are no grades, then I would have no incentive to work hard as I am not receiving anything out of it. Also, in all of my classes, the reason I listen is so that I can understand and be prepared for the test. However if there were to be no tests or results  then I would have no motivation to learn in every single class, I would only listen to those that are interesting to me. So, if there were no grades in school, then I think I would have neither motivation nor incentive to learn as much as I do with grades and results.

D.1a Origin of Life

Data-based question: the Murchison meteorite 

1. In both the Murchison meteorite and Miller-Urey experiment, glycine, alanine, isovaline, norvaline, and aspartic acid are found in equal amounts. However the Murchison meteorite contains more alpha-aminoso0butyrc acid, valine, proline, and pipecolic acid than the Miller- Urey experiment. Also, the Miller-Urey experiment contains more alpha-amino-N-butyric acid and N-ethylglycine.

2. Based on this conclusion, it seems as though meteorites could have started life on earth due to the molecules that were found.