How were lamarcks and darwin’s ideas most similar ?

Both stated that traits were passed on to offspring.

Explanation:

Jean-Baptiste de Lamarck (1744-1829) and  Charles Darwin (1809-1882) both contributed to the understanding of organism's acquired traits over a certain period of time but in different ways. Both scientists believed that organisms change gradually to better survive according to their environmental needs.

Lamarck states that changes occur during the organism's lifetime, rather than long periods of years, He gave the example of Giraffe which acquired long neck as a useful trait to reach tall trees to get food. He believed that this change happened in Giraffe's life time and this useful character was passed to the offspring.

On the other hand, Darwin believed that useful changes occur in an organism over a course of period through the process of natural selection.  According to Darwin,changes occur in specie over a course of time period to make them better adapted to environment. The organisms that are better able in surviving environmental fluctuations become successful and those that are not able to survive environmental fluctuation just die off.

However, those organisms which get successful in adapting environmental conditions transfer these useful traits to their offspring.

So what looks common in both Darwin and Lamark's theories is   Both stated that traits were passed on to offspring.

Hope it helped!