Final answer:
Darwin's fundamental insights include the common ancestry of all life, particulate inheritance, natural selection as the mechanism of evolution, and the transformation process of evolution via natural selection.
Step-by-step explanation:
Darwin's fundamental insights are:
- Common ancestry of all life on Earth: Darwin proposed that all living organisms are related and share a common ancestor.
- Inheritance is particulate: Darwin understood that characteristics are inherited in a particulate manner, meaning they are passed down through discrete units called genes.
- Natural selection is the mechanism of evolution: Darwin's most famous insight was the concept of natural selection, which explains how advantageous traits are more likely to be passed on to future generations, leading to the gradual evolution of species.
- Evolution via natural selection is a transformation process: Darwin believed that if a species changed enough, it could evolve into a new species.
Therefore, the answer is option 5: Complex organs are difficult to explain via evolution as it is not one of Darwin's fundamental insights.