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Hormone Regulation

The endocrine system is regulated through feedback loops that prevent signals from becoming too strong.

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I Thought Lemarck Was Wrong!
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Student Exploration

Lemarck Revisited

Some of you may have heard of the evolutionary theories of Jean-Batiste Lemarck (1 August 1744 – 18 December 1829). The aspect of this theory he is widely known for is "the inheritance of acquired characteristics". The example of the giraffe's (Giraffa camelopardalis) neck is often cited as an example of how this theory is wrong. However, while natural selection provides a far better explanation for the giraffe's body plan, Charles Darwin (12 February 1809 – 19 April 1882) never fully abandoned Lemarck's theories, and became increasingly Lemarkian in his later years as he struggled with the question of the source of the variation that natural selection acted upon. Darwin struggled partially through his lack of knowledge of genetics. When genetics were finally recognized as a mechanism that explained natural selection and inheritance, natural selection gained much wider acceptance in the scientific community. Unfortunately for Lemarck, this mechanism ran counter to his theories. If DNA was hard coded with information, how could acquired characteristics be passed on? Well, times change and science marches on. Scientists studying the methylation of DNA have identified a mechanism by which acquired traits can be passed to the next generation. There do appear to be limitations as far as the type of acquired information which is passed on but as far as Lemarck? Well, it seems he wasn't all wrong.

Find out more about work being done at the Salk Institute here

Extension Investigation

Use the below resources to answer the following questions

  1. How are techniques developed with the plant ‘’Arabidopsis thaliana’’ used to study human disease?
  2. Are epigenetic maps consistent throughout an organisms lifetime?
  3. What factors do scientists feel may be affecting the expression of the epigenome?
  4. Why is the epigenome called the "epigenome"
  5. How does the epigenome change through the aging process?

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