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Class 8 - BS Unit 2 (Biology 2), , , , , , 2. Cell Clusters, , * Human body is made up of millions of different kinds of cells like nerve cells, muscle, cells, blood cells and bone cells., , * Tissues :- Groups of similar cells that have a common origin and perform specific, functions., , * Animal tissues :- Epithelial tissue, Nervous tissue, Muscular tissue and Connective, tissues (blood, fibrous tissue, Cartilage, bone etc.), , * Plant tissues :- Parenchyma, Collenchyma, Sclerenchyma and Vascular tissues (xylem, and phloem), , * Animal tissues are developed from a single undifferentiated cell, called the zygote., , * Plant tissues are developed from rapidly dividing cells, called the meristematic cells., , * Cell differentiation :- The process by which all tissues are developed from a single cell., [eg:- The formation of animal or plant tissues after continuous division and changes], , , , , , , , , , , , , , , , , , , , , , , , , , ‘Sclerenchyma, , Xylem, , Phloem, , item cells :- specialized cells that can transform into any kind of cells through constant, , differentiation. Stem cells are found in the bone marrow, skin, digestive tract etc., , * Importance of stem cells ?, The research of stem cells can bring about miraculous changes in the treatment of, blood cancer, diabetes, parkinson disease etc., and also in the manufacture of, artificial organs., , Nerve cells, {zygote} ——-> [Foetal cells Bone cells, Muscle cells, Blood cells Parenchyma, 7 7 a Collenchyma, Meristematic cell| > |Meristematic tissue. as :, , * Meristematic tissue :- Specific cells seen at the tip of the stem or root in plants. They, undergo rapid division, which results in the growth of plants., * Comparison between a meristematic cell and a mature plant cell,, , [——"Meristematie cel | Mature plant cal, , - Rapidly dividing cell - No further growth by division, - Relatively large nucleus - Relatively small nucleus, , - Thin primary cell wall - Thick secondary cell wall, - More cytoplasm - Less cytoplasm, - No vacuoles - Large vacuole, , , , , * Tissues , Function and peculiarities., , 1. Epithelial tissue 1. Parenchyma, ~~ Functions such as - Composed simplest cells., protection, absorption |- Seen in the soft parts., and cell secretions. - Helps in photosynthesis and, , 2. Nervous tissue the storage of food., , - Controls and coordinates 2. Collenchyma, physiological functions and |- Composed of cells that are, responds to identify changes] thick only at the corners of, inside and outside the body. | the cell wall.