Final answer:
The Dept. of the Interior's annual lecture is named for Rachel Carson, a marine biologist who worked for the U.S. Bureau of Fisheries in the 1940s and authored 'Silent Spring'.
Step-by-step explanation:
The biologist who worked for the Dept. of the Interior in the 1940s and for whom an annual lecture is named is Rachel Carson. She was a marine biologist and author known for her groundbreaking work in environmental science, particularly with her book 'Silent Spring'. This book exposed the hazards of the pesticide DDT, leading to a revolutionary shift in environmental policies. Her significant contributions to the field and her role at the U.S. Bureau of Fisheries make her a notable figure in environmental history.
Rachel Carson continues to inspire new generations of scientists and environmentalists, symbolizing the impact an individual's work can have on public policy and environmental consciousness.