Chapter – 2:
The Invisible Living World – Beyond Our Naked Eye
Clean Study Notes with Visuals
The Invisible Living World – Beyond Our Naked Eye
1. Introduction to the Invisible World
• Many tiny living organisms cannot be seen with the naked eye.
• Magnifying glasses and microscopes help us observe microscopic life.
• Microscopes revealed a hidden world of microorganisms.
Important Point
Microorganisms exist everywhere around us.
2. Discovery of Cells and Microscope Robert Hooke
• Discovered cells in 1665 while observing cork.
• Published findings in Micrographia.
Antonie van Leeuwenhoek
• Improved microscopes.
• Observed bacteria and blood cells.
• Known as the Father of Microbiology.
3. What is a Cell?
• A cell is the basic unit of life.
• All living organisms are made of cells.
Main Parts
1. Cell Membrane
2. Cytoplasm
3. Nucleus
Plant Cell Extras
• Cell Wall
• Chloroplast
• Large Vacuole
Feature Plant Cell Animal Cell
Cell Wall Present Absent
Chloroplast Present Absent
Feature Plant Cell Animal Cell 4.
Differences
Vacuole Large Small
Between
Shape Rectangular Irregular/Round Plant and
Animal Cells
5. Variation in Cell Shape and Function
Different cells have different shapes according to their work. Examples
• Muscle Cells → help movement
• Nerve Cells → carry messages
Key Concept
Structure and function are closely related.
6. Levels of Organisation
Cell → Tissue → Organ → Organ System → Organism
• Cells form tissues
• Tissues form organs
• Organs form organ systems
7. Microorganisms
Microorganisms are tiny living organisms invisible to the naked eye.
Examples
• Bacteria
• Fungi
• Protozoa
• Algae
8. Types of Microorganisms
Protozoa
• Amoeba
• Paramecium
Fungi
• Yeast
• Mould
Algae
• Contain chlorophyll Bacteria Shapes:
• Rod-shaped
• Spiral-shaped
• Spherical
9. Importance of Microorganisms
Uses
• Decompose waste
• Clean the environment
• Improve soil fertility
• Produce biogas
Rhizobium
Helpful bacteria found in plant roots.
10. Microorganisms in Food
Yeast
Makes bread and cakes fluffy.
Lactobacillus
Converts milk into curd.
Fermentation Used in:
• Idli
• Dosa
• Bhatura
11. Microalgae
• Produce oxygen
• Food source for aquatic animals Spirulina
• Nutrient-rich superfood
Uses
• Biofuel production
• Water purification
12. Key Facts
• Cells are the building blocks of life.
• Microorganisms can be useful or harmful.
• Viruses reproduce only inside living cells.
• Bacteria do not have a true nucleus.
Quick Revision Summary
• Cell is the basic unit of life.
• Microorganisms are found everywhere.
• Plant and animal cells differ in structure.
• Useful microbes include yeast and Lactobacillus.
• Microorganisms help recycle nutrients and decompose waste.
Questions and Answers
Chapter
2:
The
Invisible Living World – Beyond Our Naked Eye
Questions and Answers
Based on
1.
What are microorganisms?
Answer:
Microorganisms are very tiny living organisms that cannot be seen with
the naked eye. They can only be seen with a microscope.
2.
Name the main types of microorganisms.
Answer:
The main types of microorganisms are:
•
Bacteria
•
Fungi
•
Protozoa
•
Algae
•
Viruses
3.
Who discovered cells?
Answer:
Robert Hooke discovered cells in 1665 while observing a thin slice of
cork under a microscope.
4.
Who is known as the Father of Microbiology?
Answer:
Antonie van Leeuwenhoek is known as the Father of Microbiology because he
first observed bacteria and other tiny living organisms.
5.
What is a cell?
Answer:
A cell is the basic structural and functional unit of life. All living
organisms are made up of cells.
6. What are the
basic parts of a cell?
Answer:
The three basic parts of a cell are:
•
Cell membrane
•
Cytoplasm
•
Nucleus
Plant cells also have a cell wall.
7. What is the
function of the cell membrane?
Answer:
The cell membrane protects the cell and controls the movement of
substances into and out of the cell.
8. What is the
function of the nucleus?
Answer:
The nucleus controls all activities of the cell and regulates growth.
9. What is the
function of cytoplasm?
Answer:
Cytoplasm contains different cell components, and most life processes
occur in it.
10. What is the role
of the cell wall in plants?
Answer:
The cell wall gives strength, support, and rigidity to plant cells.
11. What is the
difference between plant and animal cells?
Answer:
Plant cells have:
•
Cell wall
•
Chloroplasts
•
Large vacuole
Animal cells do not have a cell wall or chloroplasts, and their vacuoles
are small.
12. Why do cells
have different shapes?
Answer:
Cells have different shapes because each type of cell performs a special
function. The shape helps the cell perform its work efficiently.
13. What are
unicellular organisms?
Answer:
Organisms made up of only one cell are called unicellular organisms.
Example: bacteria and Amoeba.
14. What are
multicellular organisms?
Answer:
Organisms made up of many cells are called multicellular organisms.
Example: humans and plants.
15. What are the
levels of organisation in living organisms?
Answer:
The levels of organisation are:
Cell → Tissue → Organ → Organ System → Organism
16. How do
microorganisms help in decomposition?
Answer:
Microorganisms break down dead plants, animals, and waste materials into
simpler substances rich in nutrients. This process is called decomposition.
17. What is manure?
Answer:
Manure is a nutrient-rich substance
formed when microorganisms decompose plant and animal waste. It improves soil
fertility.
18. What is the role
of yeast in bread making?
Answer:
Yeast produces carbon dioxide during respiration. The gas forms bubbles
in the dough, making bread soft and fluffy.
19. Which bacterium
helps in curd formation?
Answer:
Lactobacillus bacteria help convert milk into curd by producing lactic
acid.
20. What is the
function of Rhizobium bacteria?
Answer:
Rhizobium bacteria live in the root nodules of leguminous plants and fix
nitrogen from the air into the soil.
21. Why are
microalgae important?
Answer:
Microalgae:
•
Produce oxygen
•
Serve as food for aquatic animals
•
Help clean water
•
Are used in medicines and biofuel production
22. Why are viruses
different from other microorganisms?
Answer:
Viruses are acellular and can reproduce only inside living cells.
23. What would
happen if microorganisms did not exist?
Answer:
Dead plants and animals would not decompose, waste would accumulate, soil
fertility would decrease, and many food products like curd and bread could not
be prepared properly.