Ecologist (noun)

1. A person who studies or is an expert in the science of ecology.
2. A person who works to protect and preserve the environment and ecosystems.

Origin:

Late 19th century: from ecology + -ist.

Examples:

1. The ecologist conducted a study on the impact of pollution on the local ecosystem.
2. She worked as an ecologist for a non-profit organization focused on conservation.
3. The ecologist gave a lecture on the importance of biodiversity to the survival of ecosystems.
4. As an ecologist, he was passionate about finding solutions to environmental problems.
5. The ecologist was a key figure in the fight against deforestation and habitat destruction.