An undergraduate degree in biology is a good choice if you want a career in a scientific field. A bachelor's degree in biology can certainly lead to future graduate studies, but even without an advanced degree, you might get a job as a science writer or research assistant, or in sales and marketing for a scientific company. The specific major you choose will play a role in what doors are open to you after college.
General biology is an obvious choice, and in some schools "biology" may be the only biology major available. In general biology, students acquire a solid background in all areas of biology without necessarily having a specific focus. This may be a good idea if you envision yourself pursuing graduate studies in biology but you're not yet sure which specific area interests you most. A degree in general biology can also be a great choice if you want to teach high school biology, and many schools offer this degree with an option for a teaching credential.
Marine biology focuses on the study of ocean-dwelling plants and animals as well as the general functioning of the ocean's ecosystem. It may be a stand-alone major or an option for a specific track in a general biology major. This major can be a good choice if you want to work in an aquarium or become a marine researcher, but you may need to seek a graduate degree or higher in order to find jobs.
Biochemistry or Molecular Biology
A major in biochemistry or molecular biology would focus on studies of life at the cellular level. You would learn about the chemical reactions inside living cells and the roles they play for the organism's overall functioning. This major can be a good choice if you are interested in research. You will need an advanced degree to work as a scientist, but a bachelor's degree could lead to a sales or administrative position in the pharmaceutical industry.
Botany is the study of plant life, and thus the major focuses on understanding plants and the roles they play in the environment. Individuals with a botany degree can find work in plant nurseries, park maintenance, gardening, agriculture, or in teaching and research. Botany may be available as a separate major in some schools or it may be a specialization for majors in general biology.
In contrast to botany, zoology is a major focusing on the study of animal life and ecosystems with a focus on animals. An advanced zoology degree will likely be required if you want to conduct research on animals or work directly with animals in a zoo or other type of park. If you hope to become a veterinarian, zoology is also an excellent choice for your undergraduate degree.
Ecology or Environmental Studies
If you are interested in issues like global warming and sustainable development, a major focused on ecology or environmental studies might suit you. Ecologists study biology at the macroscopic level, focusing on the interactions between plants and animals as well as other influences such as environmental chemicals and physical forces. This major could lead to work as a science writer, an environmental planner, a soil technician or related professions.
Microbiologists study life at the level of bacteria and viruses, which can have applications ranging from infectious disease research to public health to industrial uses of bacterial byproducts. Expect a major in microbiology to include studies of both organic and inorganic chemistry, as well as genetics and immunology. After graduation, the major could lead to work in laboratory research or in public services.
In some universities, pre-medical studies are offered as a specific major or track for college studies, but even a degree in general biology can be structured so as to make you eligible for medical school. You will need to take courses in cell biology, anatomy and physiology, physics, math and chemistry in order to meet admission requirements for medical school. If this is something that interests you, speak with a guidance counselor at your university to work out the details.