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Question

(Q1)- Explain cell and cell theory in your own words?
(Q2)- DEFINE-
(1)- Single-celled organism.
(2)- Few celled organisms.
(3)- Multi-celled organism.
(Q3)- Explain cell shape?

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Solution

(Q1)

Cell & Cell theory:

  1. ​A cell is termed as a basic unit of life as every living organism is composed of cells.
  2. This theory that cells arise only from pre-existing cells is given by Rudolf Virchow in the year 1855 and it is also called the law of cell lineage.
  3. Cell theory states that all living beings are made up of cells and the cell is the basic functional and structural unit of life. It also states that new cells arise from pre-existing cells.

The cell theory has some key points-

  1. All known living things are made up of one or more cells.
  2. All cells arise from pre-existing cells by division.
  3. The cell is the fundamental unit of structure and function in all living organisms.
  4. The activity of an organism depends on the total activity of independent cells.
  5. Energy flow occurs within cells.

(Q2)

1. Single-celled organisms: These are also called unicellular organisms. These live individually in soil, water, and air and are microscopic in nature. It can include Bacteria, Virus, Protozoa, etc.

2. Few-celled organisms: There are no proper few-celled organisms as organisms that we see today can either be unicellular or multicellular, i.e. single cell or numerous cells.

3. Multi-celled organisms: These are also called multicellular organisms. These organisms form tissues that are made of aggregation of numerous cells and that join together forming organs and finally a complete organism. e.g. Humans, Plants, Mushrooms, etc.

(Q3) Cell shape-

  1. The shape of cells might vary in organisms and also in different parts of the organism.
  2. Cells can be flat ​​​​​(Cheek cells), some are cuboidal (germ cells of gonads), columnar (intestinal cells), polygonal (liver cells), rounded (flat cells), and slipper-shaped (Paramecium), or Spindle-shaped (Muscle cells).
  3. The shape of cells mainly depends on the function it performs and the location it is present.​​

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