Explain Discovery of Cell CBSE NCERT Notes for Class 9 Science Chapter 4 Structure Of The Atom
CBSE NCERT Notes for Class 9 Science Chapter 4 Structure Of The Atom
Chapter 4 Structure of NCERT Solutions for Class 9 Science At skillyogi, the Atom gives students with answers to all of the questions in the NCERT Class 9 textbook, which is aligned with the CBSE board.
This page offers students with study source material that has been compiled by a team of subject-matter experts. Solving NCERT Solutions for Class 9 Science enables students to get the highest score on the CBSE Class 9 Science Term II test.
CBSE Class 9 Science notes will assist students in studying the topic thoroughly and clearly.
These CBSE Class 9 Science notes were written by subject experts who made the study material very basic, both in terms of language and format.
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Discovery of Cell
Under the primitive microscope, Robert Hooke (1665) studied a thin slice of cork. Cork, he discovered, consists of little box-like structures resembling honeycombs.
He dubbed these boxes cells. Cork is derived from the bark of a tree. The cell is derived from the Latin term for ‘a little chamber’. Cells have the following fundamental characteristics:
- They are capable of independence.
- They include information about a person’s ancestors.
- They are capable of carrying out all life-sustaining processes on their own.
- They are chemically related and have similar metabolic functions.
Cellular Composition in Different Organisms
They are classified into two types based on the number of cells present in various organisms:
- Multicellular organisms (having many cells).
- Unicellular organisms (having single cell)
Shape of Cells
Certain cells, such as most plant and animal cells, have a stable form, whereas others, such as WBCs and amoeba, constantly change their shape. Fixed shaped cells may be elliptical (e.g. fat cell), spherical (e.g. ovum), spindle-shaped (e.g. smooth muscle cell), knobbed thread-shaped (e.g. sperm), discoidal (e.g. RBC), or elongated (e.g. nerve cell).
Size of Cells
The size of the cell varies widely, from the smallest Mycoplasma cell (0.1-0.5 gm) to the extremely huge Ostrich egg cells (18 cm). The longest cells in the human body are the nerve cells, which may measure up to 90 cm in length.
Functions of Cells
Each living cell is capable of performing many essential processes that define living organisms.
- Multicellular organisms such as humans carry out these activities via the division of labour. Different sections of the human body are specialised to perform certain activities, such as the heart, which is designed to pump blood, the stomach, which is designed to digest food, and the kidney, which is designed to filter urine.
- Cells are defined by their shape and size in relation to the function they perform.
- Within a single cell, division of labour is also visible. Each cell has unique components referred to as cell organelles. These provide the organism with the ability to live and execute special activities.
- Organelles and protoplasm combine to form the fundamental unit of life defined as the cell. Each kind of cellular organelle serves a unique function. For instance, getting nutrients, breathing, removing waste, or producing offspring. Mitochondria is the organelle that generates energy for the cell.