Science Class 9 - Cell The-Fundamental-Unit-Of-Life Notes
Comprehensive study notes for Class 9 - Cell The-Fundamental-Unit-Of-Life olympiad preparation
Cell: The Fundamental Unit of Life
Welcome to the chapter on Cell: The Fundamental Unit of Life for Class 9. In this chapter, you will learn what cells are, their structure, types, and functions. By the end of this chapter, you will understand why cells are called the building blocks of all living things!
Introduction
All living things are made up of cells. Cells are the smallest units of life. They carry out all the basic functions needed for living.
Discovery of the Cell
- Robert Hooke discovered cells in 1665 using a microscope.
- He saw tiny box-like structures in a cork and called them "cells".
Structure of a Cell
- Cell Membrane: Outer covering that protects the cell and controls what enters and leaves.
- Cytoplasm: Jelly-like substance inside the cell where many activities happen.
- Nucleus: The "brain" of the cell. It controls all cell activities.
- Cell Wall: Found only in plant cells. It gives shape and support.
- Vacuole: Stores water, food, and waste.
- Chloroplast: Found in plant cells. Helps make food using sunlight.
Types of Cells
- Plant Cells: Have a cell wall and chloroplasts.
- Animal Cells: Do not have a cell wall or chloroplasts.
Functions of Cell Parts
- Cell membrane: Protects the cell.
- Nucleus: Controls cell activities.
- Cytoplasm: Where cell activities happen.
- Cell wall: Gives support (plants only).
- Chloroplast: Makes food (plants only).
- Vacuole: Stores things.
Why Are Cells Important?
- Cells make up all living things.
- Cells help living things grow, repair, and reproduce.
- Cells carry out all life processes.
Fun Activity: Observe Onion Cells
Take a thin peel of onion and look at it under a microscope. You will see small box-like cells!
Summary
- Cells are the basic units of life.
- All living things are made of cells.
- Cells have different parts with special functions.
Practice Questions
- Who discovered the cell?
- Name two parts found only in plant cells.
- What does the nucleus do?
- What is the function of the cell membrane?
- Why are cells called the fundamental unit of life?
Challenge Yourself
- Draw and label a plant cell and an animal cell.
- List three differences between plant and animal cells.
Did You Know?
- Some cells are so small that you need a microscope to see them!
- Red blood cells carry oxygen in your body.
Glossary
- Cell: The smallest unit of life.
- Nucleus: The control center of the cell.
- Cytoplasm: Jelly-like substance inside the cell.
- Cell wall: Outer layer in plant cells.
- Chloroplast: Part that makes food in plant cells.
Answers to Practice Questions
- Robert Hooke
- Cell wall, chloroplast
- It controls all cell activities.
- It protects the cell and controls what goes in and out.
- Because all life processes happen in cells and all living things are made of cells.
Cells are amazing! Learn more about them to understand how living things work.