PT110.S1.P3.Q15 > Analytics

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In the eighteenth century the French naturalist Jean Baptiste de Lamarck believed that an animal's use or disuse of an organ affected that organ's development in the animal's offspring. ███

Intro to Topic · Lamarckianism

Environmentally induced adaptations can somehow be inherited.

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Example · Giraffe's neck

Mama giraffe stretched its neck out to reach tall leaves (that's the environmentally induced adaptation). Somehow baby giraffe is able to inherit a long neck.

Problem with Lamarckianism · No genetic mechanism for inheritence

Biologists couldn't find genetic mechanism that could explain how baby giraffe could inherit mama giraffe's long neck.

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New Evidence · of the phenomenon

Scientists newly discovered numerous examples. I'm expecting to read on to find examples of where a mama organism's environmentally induced adaptation gets passed onto her babies.

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Example 1 · Bacteria pass on lack of walls

Environmentally induced adaptation in this case is the loss of cell walls in bacteria. This adaptation (loss of cell wall) does get passed onto subsequent generations of bacteria. The mechanism of inheritance is not via genes but rather via the interaction among genes.

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Example 2 · Genes can be added or deleted

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Example 2.1 · Fruit flies

Virus can infect fruit flies and add a gene which will get passed on. If infected flies are kept warm during reproduction, the virus is eliminated and so is the gene.

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Example 2.2 · E. coli

If an E. coli bacterium with a certain kind of gene comes into contact with another without that kind of gene, the gene can be inserted into latter, which will then get passed onto its offspring.

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Example 2.2 · Speculation

The causal mechanism found in E. coli could have helped to speed up evolution. For example, complex cells could have acquired photosynthesis by having come into contact with bacterium that possessed the photosynthesis gene.

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Implications · Gene inheritance can be "vertical" or "horizontal"

"Vertical" inheritance is what we are familiar with, inheritance of genes from from ancestors. "Horizontal" inheritance is what the previous paragraphs described: from viruses, plasmids, bacteria, or other environmental agents.

Conclusion · Horizontal transmission may be the mechanism for inheritance that Lamarck needed

Passage Style

Phenomenon-hypothesis (RC)

Single position

15.

The primary purpose of the ████ █████████ ██ ██

Question Type

Purpose of paragraph

Structure

Think about the low-res summary for the last paragraph. The primary purpose of the last paragraph is to present implications of the new evidence. The new evidence shows that Lamarck’s hypothesis might be plausible, because there is evidence of a mechanism for inheritance of acquired characteristics.

suggest a modification ██ █████████ ██████████

The author doesn’t suggest any change to Lamarck’s theory.

demonstrate the correctness ██ █████████ ██████████

Too strong. The author believes the new evidence lends support to Lamarck’s hypothesis, but that doesn’t imply the author thinks Lamarck’s hypothesis is correct.

illustrate the significance ██ █████████ ██████████

The purpose concerns the impact of the new evidence on Lamarck’s hypothesis; not the importance of Lamarck’s hypothesis.

criticize scientists' rejection ██ █████████ ██████████

This is too negative. The author doesn’t believe that scientists were wrong to reject Lamarck’s hypothesis. There was no evidence supporting it. But now that there is evidence of a mechanism for inheritance of acquired characteristics, Lamarck’s hypothesis is more plausible.

explain how recent ███████████ ███ ███████ █████████ ██████████

This best captures the purpose, which is to present implications of new research. The recent research may provide support to Lamarck’s hypothesis by providing evidence of a mechanism for inheritance of acquired characteristics.

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