Railway Science (Biology – Cell : Basic Unit of Life) (Part-II)

Tissue - A group or layer of cells that work together to perform a specific function. Types of tissue : Connective tissue, Epithelial tissue, Muscle tissue, and Nervous tissue. Connective tissues, support and connect different tissues and organs of the body, It contains three types of fibers : collagen, elastic and reticular. Discovery of Cell (Robert Hooke,1665).

Sclerenchyma - These tissues are permanent tissues made up of dead cells present in the plants. It provides hardness and stiffness to the plants. Parenchyma tissues are living thin-walled tissues that help in the storage of starch, protein, and water.
Collenchyma is also composed of thin-walled and living cells, Provides support, structure and flexibility to the young plants.
Aerenchyma is a modified parenchymatous tissue containing air chambers between cells to allow gasses to diffuse and provide buoyancy to aquatic plants.

It is the internal spherical structure of the cell containing the genetic material. It is bound by a nuclear membrane and it controls the activity of all the other organelles of the cell.
Mitochondria (Powerhouse of the cell) is a rod shaped structure which is found in animal and plant cells; its function - Production of energy (in the form of ATP), regulation of immunity, stem cell regulation.
Endoplasmic reticulum - It is a large, dynamic structure that serves many roles in the cell including calcium storage, protein synthesis and lipid metabolism.

Arteries play a major role in nourishing organs with blood and nutrients. These are always under high pressure. To accommodate this stress, they have an abundance of elastic tissue and less smooth muscle.
Heart is a fist-sized organ that pumps blood throughout the body. Epithelial tissues are widespread throughout the body.
They form the covering of all body surfaces, line body cavities and hollow organs, and are the major tissue in glands.

The discovery of the structure of DNA and its role in heredity is attributed to James Watson and Francis Crick. The term ‘Genetics’ was coined by William Bateson in the year 1905. In human beings, in each cell, there are 46 (23 pairs) chromosomes.
Twenty-two of these pairs are autosomes and the 23rd pair, the sex chromosome differs in males and females. Females have 2 copies of the X chromosome while males have one X and one Y chromosome.