Neo-Lamarckism

• Lamarckism: Acquired characters arise mainly due to needs of the organism.
• Neo-Lamarckism: Acquired characters arise mainly due to the environment and habit.

• It accepts the inheritance of acquired characters.
• It gives strong importance to environmental conditions in bringing about change.
• It considers habit as an important factor in the modification of characters.
• It attempts to support Lamarckian ideas through experimental observations.

Tower reported that potato beetles exposed to abnormal temperature and moisture conditions produced offspring that were markedly different from their parents, and these changes were said to be inherited.

• Condition: Abnormal moisture and temperature.
• Observation: Offspring differed noticeably from the parent beetles.
• Inference: Environmental conditions were thought to induce heritable changes.

Rough, non-type-specific forms of type III pneumococci change into smooth type III pneumococci when exposed to extracts of dead smooth type III pneumococci.

• Initial form: Rough, non-type-specific pneumococci
• Treatment: Exposure to extracts of dead smooth type III pneumococci
• Observation: Conversion into smooth type III pneumococci
• Inference: External influence can lead to a change in character

• Neo-Lamarckism is a modified version of Lamarckism which states that acquired characters are caused by environment and habit rather than the internal needs of the organism.
• It accepts the inheritance of acquired characters and strongly emphasises the environment's role in modifying these traits.
• Unlike the original theory, Neo-Lamarckism relies on direct experimental observations to support its claims.
• Tower’s potato beetle experiment demonstrated that abnormal environmental conditions, such as temperature and moisture, can induce heritable changes in offspring.
• The pneumococci experiment showed that external influences can alter characteristics, as rough bacteria transformed into smooth ones when exposed to dead smooth extracts.