CHAPTER1 THE CELL ITS STRUCTURE AND FUNCTIONS Cell

CHAPTER-1 THE CELL- ITS STRUCTURE AND FUNCTIONS

• Cell is the basic structural as well as functional unit of all living organisms. • Certain basic functions like, nutrition, respiration, growth, development and reproduction are performed by the cell in all organisms.

• Robert Hooke was the first scientist, who in 1665, observed thin slices of cork (obtained from the bark of a tree) through his self designed microscope. • He observed that they had honey comb like structure consisting of little compartments. • These compartments were actually dead cells bound by a cell wall.

UNICELLULAR AND MULTICELLULAR ORGANISMS • On the basis of their number of cells living organisms can be classified into two categories: unicellular and multicellular organisms.

• Organisms which consists of a single cell are termed unicellular. For example- Euglena, Amoeba, Paramecium, etc. • Organisms made up of many cells are termed multicellular. For example- Humans, Birds, Animals, etc.

CELL SHAPE • The cell shapes may be oval, spherical, cuboidal, fiber-like, or polygonal. • Cells have different shape due to their location and function in the tissue. • A nerve cell has to transmit impulses to organs located in different parts of the body, hence they possess a fiber-like structure.

CELL SIZE • Smallest cell: mycoplasma/ PPLO/ Pleuro pneumonia-like organisms (0. 1 micron) • Largest cell: ostrich egg(170 mm in diameter)

ACTIVITY-1 Given below are the links of You. Tube on how to prepare temporary mount of onion peel and cheek cell. • https: //youtu. be/cmnh. BJKfv. Nw • https: //youtu. be/tm. Ra 8 u. TG 7 e. Q

PICTURE GALLERY EUGLENA AMOEBA

PARAMOECIUM CHLAMYDONOMAS

LIVER CELL FAT CELL

RED BLOOD CELL SMOOTH MUSCLE CELLS

CROSS SECTION OF HEN’S EGG Refer to activity-1 , page-4 of science book ‘The Living World’-8

GREEN ALGAE- CHARA

HUMAN OVUM

ASSIGNMENT-1 GIVE ONE WORD FOR THE FOLLOWING: 1. The basic structural and functional unit of life: ____ 2. The scientist who discovered cell: _______ 3. Animals that consists of single cell belong to the category of_______ 4. Animals that consists of many cells belong to the category of_______ 5. Cells possessing fiber like structure: ____ 6. Smallest cell: _____ 7. Largest cell: ______ 8. Smallest human cell: _____ 9. Largest human cell: ______ 10. The reserve food material in the cytoplasm of hen’s egg: _______