The hardest biology major is Biochemistry, followed by Molecular Biology and Molecular Cell Biology.
All 3 of these biology majors require that you have a strong foundation in technical biology, mathematics and chemistry along with the ability to memorize complex vocabulary and also be able to understand technical processes.
Both Molecular biology and Biochemistry are fields that combines the intricacies of biochemistry which is "the study of chemical processes within living organisms" with molecular biology which is "the study of molecules which are essential to life".
Biochemistry and molecular biology require a strong understanding of chemistry, biology and mathematics, as well as the ability to memorize a large number of complex concepts and terms.
Molecular Cell Biology is a major that focuses on the structure and the function of cells at the molecular level, which includes the study of nucleic acids, proteins and molecular mechanisms of immunology, cancer and genetic engineering.
Molecular cell biology also involves the strong understanding of genetics, microbiology and animal as well as plant biology and can require a lot of math.
Both majors require that you grasp complex areas in biomedicine and biotechnology and there's also a misconception that biology doesn't involve much math, although that is not true, especially when it comes to genetics.
Other challenging majors and career paths can be in research, medicine, biotechnology and many other fields as well.
The biology major that is often the easiest is environmental science.
A biology major in environmental science often involves more hands on work and less complex math than other areas of biology.
Similarly, some students find plant biology or evolutionary biology less mathematically intensive than molecular biology or biochemistry.