Naturalist (noun)

1. A person who studies or is an expert in natural history, which is the study of plants, animals, and other organisms and their relationships to each other and to the environment.
2. A person who advocates or follows a lifestyle or philosophy that is in harmony with nature.

Origin:

From latin naturalis, from natura "nature".

Examples:

1. The naturalist studied the plants and animals in the forest.
2. The naturalist's observations were important in understanding the ecosystem.
3. He was a naturalist and an advocate for conservation.
4. The naturalist's book was a bestseller and helped raise awareness about endangered species.
5. As a naturalist, he believed that humans should live in harmony with nature.