12th Zoology

Neo lamarckism

Neo lamarckism

Lamarck’s ‘theory of inhertitance’ was further studied by a group of
scientists. Their ideas supporting Lamarck’s opinion collectively constitute
neo Lamarckism.

The neo Lamarckians were of the opinion that ‘adaptions’ are
universal in nature. An adaptation happens through causal relationship of
structure, function and environment. Due to changes in the environment, habits
and life style of organism gets altered. Thus gradually the organism acquires
new structures. The newly obtained character gradually becomes an
inheritable trait. This opinion and argument is a modified form of
Lamarckism. These ideas stressed direct action of environment on organisms.
Support to neo-Lamarckian concept – Experiments (Neo lamarckism)

Neo Lamarckism

1. McDougall (1938) tried to prove that learning is an acquired character
that can be inherited. He did his experiments on rats.

He deviced a ‘T’ shaped tank. The tank had two exits. One exit was
well lighted. However at the terminal region of the exit he deviced an
arrangement for giving electrical shock. The pathway to the other exit was
kept dark. At the terminal exit point a small piece of cheese was kept as a
reward. McDougall dropped several rats into the tank. Many of the rats
preferred lighted pathway to escape and at the exit they received electric
shock. Those rats, that preferred dark pathway received the cheese. He
repeated the trial several times. Gradually many rats learnt the correct route
for escape. Subsequently the rats were allowed to breed and the next
generation developed.
The same experiment was repeated in the second generation. (Neo lamarckism)

According to Mc Dougall, it was claimed that the number of mistakes
committed, gradually got reduced. The speed of learning increased from generation to generation. Thus he concluded that learning is an acquired

However later workers found some technical mistakes in the work
of Mc Dougall. The same experiment while repeated in other laboratories
failed to give similar results. (Neo lamarckism)

2. Temperature related changes in the body of mice was noted by F.B.Sumner
(1910). He reared one set of white mice in warmer temperature (20 – 300c)
and another set in cold conditions. He found that in warmer conditions the
mice developed larger ears and longer tails. He further claimed that these
characters were inherited.

Through similar works claim for inheritance of acquired characters
were made by Lindsey, Guyer and Smith and Kammerer. In all these works
while repeating, critics have found technical mistakes and rejected them

However, the controversy over ‘inheritance’ of acquired characters
still continues. This theory of Lamarck while has not been disproved totally,
it remains to be proved correct. (Neo lamarckism)

Related Topics in Zoology:

Bio Zoology All Important Topics

  1. Livestock and Management

  2. Important cattle breeds and their characteristics

  3. Milch breeds (or) Dairy breeds

  4. Dual purpose breeds & Draught breeds

  5. Exotic breeds of cattle

  6. Common diseases and control in Cattle – Contagious diseases

  7. Non-contagious diseases – Cattle

  8. Techniques adopted in cattle breeding

  9. Poultry Breeds

  10. Farming methods

  11. Poultry byproducts

  12. Fish Pond

  13. Edible Fishes Of Tamilnadu

  14. Medical Lab Techniques – Stethoscope

  15. Sphygmomanometer

  16. Haemocytometer

  17. Urine Sugar analysis

  18. ECG Electrocardiogram

  19. Computed Tomography CT

  20. Endoscopy (Laproscopy) techniques , Artificial Pacemaker

  21. Autoanalyser

Unit 7. THEORIES OF EVOLUTION Topic List Zoology

  1. Theories Of Evolution Introduction

  2. Lamarck Laws

  3. Neo Lamarckism

  4. Darwinism

  5. Theory of Natural Selection

  6. Objections to Darwinism

  7. Modern concept of Natural Selection

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