Sourav Pan is the founder and sole author of Biology Notes Online. He holds a Bachelor of Science (B.Sc.) degree and an M.Sc. in Microbiology from the University of Calcutta. He creates educational resources covering microbiology, immunology, biotechnology, genetics, cell biology, botany, zoology, and other life-science subjects.
His goal is to make complex biological concepts easier to understand through well-structured, student-friendly articles based on academic textbooks, peer-reviewed research, and authoritative scientific sources. In addition to writing new content, he regularly reviews and updates articles to improve their accuracy, clarity, and educational value.
What is Rolling circle replication? Rolling circle replication is a unidirectional and asymmetric process of nucleic acid replication. It is the process by which multiple copies of circular DNA or RNA molecules is synthesized rapidly. This mechanism is commonly seen in bacterial plasmids, bacteriophages and certain plant and animal viruses. In this type of replication … Read more
Chemical Oxygen Demand (COD) is a way to measure how much oxygen is needed to chemically oxidize organic and some inorganic substances in water that is acidic and has a strong oxidant, like potassium dichromate. It is usually shown in mg O₂ per liter. To find out how much oxidizable material is in a sample, … Read more
A dry mount slide is the simplest type of slide preparation in microscopy. It is the process in which a dry specimen is placed directly on the clean glass slide without using any liquid medium. It is the air that remains between the specimen and the objective lens, and the refractive index of air is … Read more
What is Animal Behaviour? Animal behaviour is the study of the activities and responses shown by animals in relation to their environment and other organisms. It includes all the actions that animals perform during their life such as searching for food, finding shelter, avoiding enemies, communication and reproduction. These activities help the animal to survive … Read more
Onion cells are plant cells obtained from the thin epidermal layer of an onion (Allium cepa). This layer is peeled from the inner surface of onion scale and placed on a clean glass slide. The cells are transparent, so iodine stain is generally used for better observation. Under low magnification, onion cells appear as closely … Read more
Inflammation is a protective reaction of body against injury, infection and harmful substances. It is a part of innate immune system. It helps to remove the harmful agent and starts tissue repair.Inflammation is a protective defence reaction of the body which occurs against infection, toxic chemical, injury and tissue damage. It is a part of … Read more
Innate immunity is the natural defence system of the body which is present from birth. It gives immediate protection against invading pathogens like bacteria, viruses, fungi and parasites. It acts in a non-specific manner and does not require previous exposure to the antigen. Innate immunity is the first and primary defence system of the body … Read more
Definition of Pseudostratified columnar epithelium A pseudostratified columnar epithelium an epithelium made up of only one layer of cells which creates the appearance of multiple layers due to the nuclei in the cells are located at various levels. It is histologically an epithelium that is simple, even though when viewed from a cross-section it could … Read more
Principles Of Biotechnology Biotechnology has grown and changed a lot over the years. The old way of doing it was to use microbes to make products that people could use. Now, the new way is to use genes to make vaccines. So, the European Federation of Biotechnology (EFB) has come up with a new definition … Read more