The specialist caterpillars of the monarch butterfly

(Danaus plexippus) are insensitive to the terpenoid toxins. They feed on milkweed leaves and retain the cardenolides. As a result, most insectivorous birds quickly learn to avoid eating monarch caterpillars and adult monarch butterflies.

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Just as muscles become strengthened by work, more strongly exercised organs attract and become enlarged by the “nervous fluid.” 

Acquired during an individual’s lifetime, are inherited—a principle called inheritance of acquired characteristics.

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In the most famous example of Lamarck’s theory, giraffes must have stretched their necks to reach foliage above them, and so their necks were lengthened

The longer necks were inherited, and over the course of generations, this process was repeated, and their necks got longer and longer. 

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Neo-Lamarckism - August Weismann

cut off the tails of mice for many generations and showed that this mutilation had no effect on the tail length of their descendants.

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Darwin’s evolutionary theory 

Evolution as such is the simple proposition that the characteristics of organisms change over time.