Thursday, July 16, 2020
Group of cells tissue
● Groups of cells that have the same structure and function are called tissues. Examples of blood, phloem, and muscle tissue are.
● Trees are stable, they do not move but grow. Most of the tissue of the plants are supporting the plant and provide structural strength (shape) to the plants, so that the plants stand upright. Most such tissues are dead. These dead tissues provide the same mechanical strength as living tissues and do not require much maintenance.
● Tissues are arranged in a specific order to function smoothly.
● Growth of plants is limited in some areas whereas in animals it is not. Some tissues of plants continue to divide lifetime.
● In unicellular organisms, all fundamental functions are performed by a single cell. In amoeba, the speed, food intake, respiration and excretion are all done by a single cell.
● Multicellular organisms have millions of cells. Most of these cells are capable of performing only a few functions. These organisms have different groups of cells to perform different functions, that is, division of labor.
● The internal cells of the body which are capable of performing similar tasks are always in groups.
● The contraction and expansion of muscle cells causes motion in the body.
● The function of nerve cells is to pass the sensations to the brain and the messages from the brain to other parts of the body.
● The function of blood cells is to carry oxygen, food, hormones and waste materials.
● Conduction tissue carries food and water from one part of the plant to another.
● Plants grow only in certain and special parts of them. It is due to the dividing tissues that such dividing tissues are located in the growth parts of the plants. Such tissues are called meristematic tissues.
● The meristematic tissue loses its ability to grow and divide, which results in the formation of permanent tissue. The cells of the meristem divide and form different types of permanent tissues.
● The differentiation of the permanent form and shape of the tissue to perform a specific function is called differentiation.
● Cells that differentiate and perform specific functions and lose the power to divide, this type of tissue is called permanent tissue.
● Tissues that are made up of the same type of cells and look alike are called simple permanent tissues. Examples: Parenchyma, Collenchyma and Scarenchyma etc.
● Scarenchyma: A type of simple permanent tissue that makes plants hard and strong. Example: coconut peel.
● Collenchyma: Another type of simple permanent tissue that provides flexibility to plants.
● Lignin: It is a chemical substance that acts as a cement to make cells strong.
● The outermost layer of cells is called epidermis. Generally it is made up of a layer of cells. Plants found in dry places may have thicker epidermis.
● In the epidermis of desert plants, a chemical substance called cutine is found which has the properties of water inhibitor.
● Many small holes are found on the surface of the leaves, these holes are called stomata.
● Two kidney-shaped cells surround the stomata, which are called protective cells. Protective cells are required to exchange gases from the atmosphere.
● The process of water degradation in the form of water vapor is called evaporation.
● Xylem is a convection tissue and forms a convection bundle. Xylem is made up of tracheids (vahinica), vasculature, xylem parenchyma and xylem fiber.
● Phloem is also a convection tissue and forms convection bundle. Phloem is made up of four types of components - sieve tubes, companion cells, phloem parenchyma and phloem fibers.
● Xylem combines with phloem to form convection bundles and provide mechanical strength to plants due to the presence of lignin cells.
● Food and nutrients like sugars and amino acids are transported from the leaves of the plant to the growth part and storage organs. This process is called transfer.
● The tissue covering the body of the animal or providing external defense is called epithelium tissue. Skin, mouth, esophagus, blood vessel lining, lung lumen, renal tube etc. are all made up of epithelium tissue.
● Sometimes some part of epithelial tissue is turned inward and forms a multicellular gland. This multicellular gland is called glandular epithelium.
● Blood is a connective tissue that acts as a medium for the convection of substances. Conducts blood gases (oxygen and carbon dioxide), digested food, hormones and excretory substances from one part of the body to another.
● The liquid half of the blood is called plasma.
● Plasma contains suspended red blood cells (RBCs), white blood cells (WBCs) and platelets. Plasma also contains proteins, salts and hormones.