What evolutionary study in the early 19th century focused on what two hereditary issues?

In the early 19th century, evolutionary studies, particularly those influenced by the work of figures like Jean-Baptiste Lamarck and later Charles Darwin, focused on hereditary issues related to the inheritance of acquired characteristics and the variation of traits within species. Lamarck proposed that organisms could pass on traits acquired during their lifetime to their offspring, while Darwin emphasized natural selection as a mechanism for evolution, highlighting the importance of heritable variation in adapting to changing environments. These ideas laid the groundwork for modern genetics and evolutionary Biology.