Week 4/Genomics 2016/Yoon Changhan

Plan

How molecules and cells propagate in the universe? Evolution.

Close species Comparative Genomics (CSCG) for diverse genome evolution.

Phylogenetic tree.

Evolution

 

Homework [1]

 

Darwin confessed, "To suppose that the eye with all its inimitable contrivances for adjusting the focus to different distances, for admitting different amounts of light, and for the correction of spherical and chromatic aberration, could have been formed by natural selection, seems, I freely confess, absurd in the highest degree.

 

 

 

Evidences to Redress Darwin's Theory of Evolution

 

Changhan Yoon

 

Abstract

 Darwinism is a theory of biological evolution developed by English naturalist Charles Darwin, stating that all species of organisms arise and develop through the natural selection of small, inhereted variations that increase the individual's ability to compete, survive and reproduce. Pangenesis, which is a theory of heredity hypothesized by Darwin, was supporting Darwinism as it explained heredity of variations. I found that Gregor Mendel's experiments and other evidences attacked Darwinism by refuting pangenesis. Hence, Darwinism supported by pangenesis is not perfect to explain the biological evolution.

 

Introduction

 Since 1832, when Charles Darwin arrived at Galapagos islands where various traits and species exists, the concept of evolution has been considered as one of the most powerful tool to explain the variety and origin of life. But, as crucial evidences and theories such as Mendel's law of inheritance emerged, the theory of evolution has been changed gradually, which makes the first model obsolete.  Through that way, we are ignorant about what Darwin's original theory tried to say. Now, in this essay, we want to focus more about Darwin's first model and criticize it on many biological terms.

 

Darwin's Explanation : Gemmule and Pangenesis

 Observing taxidermied birds' traits, Darwin found that there are correlation between their specific traits and their habitats. He had inspiration from Hippocrates's view on the topic, which made Darwin establish and publish his view with "pangenesis". Pangenesis was Darwin's model to explain the mechanism for heredity and evolution using imagined particles named as gemmule which appeared in his book 'The Variation of Animals and Plants under Domestication', pubilshed in 1868, nine years after pubilcation of his famous book 'On the Origin of Species'. 

 Gemmules were assumed to be spread within all parts of body and carried in the bloodstream to the reproductive organs where they accumulated in germ line cells. Gemmules were also able to be changed easily affected by surroundings or natural pressures. It seemed to explain well how acquired traits are inhereted, yet there were lots of problems preventing it accepted.

Defects on Pangenesis

1. Pangenesis can not explain Mendel's Cross expriments.

 Gregor Mendel's study totally defeated Darwin's mechanism. Mendel proved that heredity has at least one certain discrete unit to express one trait. Unfortunately gemmule couldn't be that unit as it was continuous concept and did not have method to explain law of dominance, segregation and independent assortment..

2. Acquired traits are not inherited.

 Lamarckism was very similar to Darwinism in that both were trying to explain that evolution occured within relatively short time. Both are not true because acquired traits are not inherited (but epigenome), which cannot affect phynotypes. 

3. Pangenesis can not explain asexual propagation

 According to the pangenesis, gemmule should be inhereted by sexual propagation. However, there are many asexual reproductions such as binary fission, budding, and vegetative propagation.

 

Reference

https://en.wikipedia.org/wiki/Pangenesis

https://en.wikipedia.org/wiki/Gemmule_(pangenesis)

https://en.wikipedia.org/wiki/On_the_Origin_of_Species