Biology

The body wall of the earthworm is covered externally by a thin non-cellular cuticle below which is the epidermis, two muscle layers (circular and longitudinal)…

Earthworms have long cylindrical body. The body is divided into more than hundred short segments which are similar (metameres about 100-120 in number). The dorsal…

Earthworms are classified in the phylum Annelida or Annelids. Earthworm is a reddish brown terrestrial invertebrate that inhabits the upper layer of the moist soil. They…

The granular, transparent and homogeneous liquid substance present in the nucleus is known as nucleoplasm. It is the substance of a cell nucleus, especially that…

The transparent, semi-permeable and flexible membrane around the nucleus is said to be the nuclear membrane. Structure: It is a porous and two-layered membrane. It…

The most conspicuous organelle in a living cell is usually round, surrounded by lipo-protein made membrane which contains chromosomes and regulates all the activities of…

Neural tissue exerts the greatest control over the body’s responsiveness to changing conditions. Neurons, the unit of neural system are excitable cells (Figure). The neuroglial…

Each muscle is made of many long, cylindrical fibers arranged in parallel arrays. These fibers are composed of numerous fine fibrils, called myofibrils. Muscle fibers…

Loose connective tissue has cells and fibres loosely arranged in a semi-fluid ground substance, for example, areolar tissue present beneath the skin. Often it serves…

Bones have a hard and non- pliable ground substance rich In calcium salts and collagen fibres which give bone its strength. It is the main…