pls tell the summy of chapter 8 the unit of life
Answers
Answer:
Cell is the basic unit of life.
Explanation:
CELL: THE FUNDAMENTAL UNIT OF LIFE
Cell: Cell is called the fundamental unit of life.
A cell is capable of independent existence and can carry out all the functions which are necessary for a living being. A cell carries out nutrition, respiration, excretion, transportation and reproduction; the way an individual organism does. Unicellular organisms are capable of independent existence which shows a cell’s capability to exist independently. Due to this, a cell is called the fundamental and structural unit of life. All living beings are composed of the basic unit of life, i.e. cell.
CELL THEORY (Schleiden, Schwann and Virchow):
All living organisms are composed of one or more cells.
The cell is the basic unit of structure, function, and organization in all organisms.
All cells come from preexisting, living cells.
STRUCTURE OF CELL
Shape and Size of Cells: Cells come in all shapes and sizes. While most of the cells are spherical in shape, cells of various other shapes are also found. Most of the cells are microscopic in size, i.e. it is impossible to see them with naked eyes. Some cells are fairly large, e.g. a neuron in human body can be as long as 1 meter. The egg of an ostrich is the largest known cell of a living animal and an average egg is 15 cm long and 13 cm wide.
A cell is enclosed in a membranous casing and is filled with a liquid substance which is called the cytoplasm. There are many cell organelles in a typical cell. Some of the main structures of a cell are as follows:
Cell wall: Cell wall is made of cellulose. It is somewhat hard but permeable to most of the substances. Cell wall is available in plant cells and in cells of bacteria and fungi.
Plasma membrane: Plasma membrane is a semi-permeable membrane. It is composed of bilayer of lipid and protein.
Functions of Plasma Membrane: Plasma membrane provides a container to the cytoplasm. It facilitates passage of various substances in and out of the cell.
Nucleus: Nucleus is covered by double membrane; called nuclear membrane. The fluid which is inside the nucleus is called nucleoplasm. Nucleus contains chromosomes which are important for the functioning of a cell. Chromosomes contain genes which are the carriers of genetic information. Nucleus plays an important role during cell division.
Plant Cell Vs Animal Cell
Plant cellAnimal cellCell wall presentCell wall absentPlastids presentPlastids absentVacuole is usually very large and singleVacuoles are much smaller an may be absent
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