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Lamarck and Darwin: Summary of Theories

Lamarck and Darwin: Summary of Theories Compilation of images of Lamarck, by Charles Thévenin [Public domain], and Darwin, by George Richmond [Public domain], via Wikimedia Commons

Introduction

This chart will help you to compare Lamarck's mechanism for evolution with Darwin’s theory of natural selection.


  Jean Baptiste de Lamarck Charles Darwin
Conception of species:

Population of individuals all of the same kind (identical characteristics in all members). Individuals capable of transformation.

Population of interbreeding individuals with similar characteristics, though variation is common among all of them at all times. Individuals fixed and unchanging. Population capable of transformation.

Mechanism of new species production:

Internal drive toward greater complexity modified by the inheritance of acquired characteristics. Change directed to meet organism needs.

Natural selection. Variation exists regardless of organism's needs not directed toward any purpose.

Example of this type of explanation:

The giraffe's neck: “At some point in the past, giraffes must have found themselves in an environment where they had difficulty reaching food present on the tops of trees. In order to eat, they must have had to stretch their necks and in doing so physically elongated them some. This longer neck was passed on to the offspring in the next generation, who in turn stretched their necks even further, thus resulting in the giraffe species having very long necks."

Keen eyesight of the hawk: “In a  population of hawks, individual  variation existed in the power of  their vision, just as variation exists  in the color of their feathers. In  their competition for food, the  individuals with keener eyesight  could more easily spot their prey  (small voles and mice) and thus  were successful in securing food to  eat. The hawks with poor eyesight  had difficulty spotting prey and  died for lack of food. The hawks  with the keen eyesight passed on  this trait to their offspring. The  hawks that died were not able to  produce any offspring. Over a  number of generations, the  population of hawks all came to  possess extremely powerful vision."

Phenomena the model can account for: • Adaptation
• Fossil record
• Adaptation
• Fossil record
• Homologous structures
• Biogeographical diversity patterns

 

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