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.
Definition Glandular epithelium The glandular epithelium comprises a set of tissues that is not the epithelium that covers and lines that is specifically designed to secrete and produce of different macromolecules. Due to its primary role it is often referred to as”the secretory epithelium. It is situated under the lining and covering epithelium. It may … Read more
What is hypotonic solution? Definition of Hypotonic solution A hypotonic solution is one that has a lower solute concentration compared to another solution, leading to a net movement of water into the region of higher solute concentration, typically across a semipermeable membrane. What Happens to Cells when it is placed in a hypotonic Solution? When … Read more
To function properly, cells must be kept turgid. To function properly, a well-watered plant will grow and produce fruits and flowers. A plant that is not watered for several days will wilt and eventually die. This happens because water leaves the cell and causes the cell to lose its turgidity. Based on the concentration of … Read more
What is An Autotroph? Definition of Autotroph An autotroph is an organism that can produce its own complex organic compounds (like carbohydrates) using simple substances such as carbon dioxide, typically through processes like photosynthesis or chemosynthesis, without relying on external sources for carbon or energy. Types of Autotrophs Autotrophs, which are organisms that make their … Read more
What is Heterotroph? Definition of Heterotrophs Heterotrophs are organisms that rely on eating other living things for their nutrition and energy, as they cannot produce their own food. Types of Heterotrophic Nutrition In the natural world, living things use different ways to get their food when they can’t make it themselves. These are the main … Read more
What are Phylum Mollusca? Definition of Mollusca (Mollusks) Mollusca, commonly known as mollusks, is a large phylum of invertebrate animals characterized by a soft body that is often protected by a hard shell. This diverse group includes species such as snails, slugs, clams, octopuses, and squids. Mollusks are known for their unsegmented bodies, bilateral symmetry, … Read more
Definition of Phylum Nematoda Nematodes (Gr. nema thread+ form) are often referred to by various names, such as threadworm, non-segmented roundworm or pinworm. They are distinct from flatworms and higher segmented anelids. Characteristics of Phylum Nematoda Classification of Phylum Nematoda Nematoda is one of the most diverse phyla. At present, there are approximately 15,000 species. … Read more
Definition of binary fission (What is binary fission?) Binary fission can be described as a kind of sexual reproduction in which one living cell, or organelle expands twice its size, and then splits into two identical cells, which means that each of the daughter cells can be expected to grow to what size as the … Read more
What is Monera? Definition of Monera Monera is a historical biological kingdom encompassing prokaryotes, which are unicellular organisms lacking a distinct nucleus. This kingdom primarily included bacteria and archaea, and its members are characterized by the absence of membrane-bound organelles. Over time, taxonomic classifications have evolved, and the term “Monera” is less commonly used today. … Read more
Definition of Mesophyll Cells The mesophyll cell is a group of highly differentiated cells which make up the mesophyll layer in plant leaves. The mesophyll layer in the leaves of dicotyledonous plant species is made up two types of cells: the spongy, and the palisade. This makes the mesophyll a site of photosynthesis. These are … Read more