Question

Fundamental unit of life

Explain Unicellular and Multicellular organisms .

Explain Struchral Organisation of cell .

Explain Shape of Cell

Class 9
Science ​

Answer 1

1. Explain Unicellular and Multicellular Organisms.

Answer -:

There are two types of organisms on the basis of the number of cells they have. They are -:

• Unicellular Organisms
• Multicellular Organisms

Unicellular Organisms

• As the word suggests, "uni" means one and "cellular" means cell. So, unicellular organisms are those organisms that have only one cell.

• All life functions are carried out by this one particular cell.
• For Example -: Paramecium, Yeast, Bacteria, Amoeba, etc.

Multicellular Organisms

• As the word suggests, "multi" means many and "cellular" means cell. So multicellular organisms are those organisms that have multiple or more than one cell.
• Different life functions are carried by different cells.
• For Example -: Plants, Human beings, Lion, etc.

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2. Explain the Structural Organisation of Cell.

Answer -:

• The thin outer covering of the cell is known as the cell membrane. Components of the cell are enclosed in this membrane. It is a semi-permeable membrane and controls the entry and exit of substances within the cell.

• Cell wall is a rigid and hard outer layer of the plant and some bacteria. They are fully-permeable and allow the entry and exit of all molecules.

• Cytoplasm is a jelly-like, cell fluid that fills the spaces in the cells. All cell organelles are present in the cytoplasm. It controls bio-chemical reactions (metabolism) within the cell and is a part of the protoplasm.

• Nucleus is present in the center of the cell in animal cells and in the corner in plant cells. It controls the functions of the cell. It is also known as the brain of the cell. It consists of chromosomes that have hereditary unit, the DNA, which passes from the parent to the offspring. It controls the character of the organism.

• The nucleus has a small tiny round structure known as the nucleolus that performs ribosome biogenesis.

• The mitochondria helps in the production of energy in the form of ATP molecules.

• Plant cells consist of plastids. They are of three main types → Chromoplasts, Chloroplasts and Leucoplasts.

• Lysosomes are also known as suicide bags and they clean up the cells by eating/digesting foreign materials or damaged cell organelles.

• Golgi Apparatus carries out the processing of proteins that are produced by the Endoplasmic Reticulum.

• Vacuole in plant cells helps in maintaining the balance of water. They are present in the center.

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3. Explain the Shape of Cell

Answer -:

Different cells have different shapes depending on their functions they perform. Mostly cells are spherical in shape, like the RBCs. Cells may be elongated and branched as well, for example, the nerve cell or the neuron. They are elongated and branched so they can easily paṩs the signals from one cell to the other.

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