It's difficult to call any branch of biology truly "minor" as they all contribute to our understanding of life. However, some branches are indeed more specialized or less well-known than others. Here are a few examples, grouped by their focus:

Focusing on specific organisms:

* Bacteriology: The study of bacteria

* Mycology: The study of fungi

* Virology: The study of viruses

* Entomology: The study of insects

* Ichthyology: The study of fish

* Herpetology: The study of amphibians and reptiles

* Ornithology: The study of birds

* Mammalogy: The study of mammals

Focusing on specific aspects of life:

* Biochemistry: The study of chemical processes within living organisms

* Biophysics: The study of physical principles applied to biological systems

* Biomechanics: The study of the mechanics of living organisms

* Developmental biology: The study of the development of organisms

* Ecology: The study of the interactions between organisms and their environment

* Evolutionary biology: The study of the origin and diversification of life

* Genetics: The study of heredity and variation

* Immunology: The study of the immune system

* Microbiology: The study of microorganisms

* Molecular biology: The study of biological processes at the molecular level

* Neurobiology: The study of the nervous system

* Physiology: The study of the functions of living organisms

* Zoology: The study of animals

Focusing on specific applications:

* Biotechnology: The use of biological systems for technological purposes

* Bioinformatics: The use of computers and software to analyze biological data

* Conservation biology: The study of the conservation and protection of biodiversity

* Forensic biology: The application of biological principles to legal investigations

* Marine biology: The study of marine organisms and ecosystems

* Paleontology: The study of prehistoric life

This is just a small selection of the many branches of biology. There are many other specialized fields, often overlapping with each other, and new areas of research are constantly emerging.

It's important to note that the distinction between "major" and "minor" branches can be subjective and depends on individual perspectives and research interests. Each branch of biology is essential for understanding the complex and fascinating world of living things.