You are here
Why does the invisible living world matter?
All living things are made of cells
The cell is the basic unit of life
↓
Cells group together
Forming tissues, organs, and a body
↓
Some living things are single-celled
These tiny microbes are everywhere
↓
Microbes act on waste and food
Making manure, curd, and oxygen
↓
The invisible living world supports life on Earth
The Invisible Living World
Class 8 — Chapter 2
2.1
The Cell
membrane, cytoplasm, nucleus; plant vs animal cell
2.2
Levels of Organisation
cell, tissue, organ, organ system, organism
2.3
Microorganisms
protozoa, algae, fungi, bacteria; microscope
2.4
Connected to Microbes
decomposition, manure, biogas; food and microbes
2.4.2–3
Food & Microalgae
yeast, Lactobacillus, Rhizobium, Spirulina
2.5
Basic Unit of Life
cell carries out life; bacteria have a nucleoid
Key Terms
- Cell
- The basic building block of all living things.
- Cell membrane
- The outer layer that controls what enters and leaves the cell.
- Cytoplasm
- The jelly-like material inside the cell where most life processes happen.
- Nucleus
- The round central part that controls the cell's activities and growth.
- Cell wall
- An extra strong outer layer found in plant, fungal, and bacterial cells.
- Tissue
- A group of similar cells working together.
- Organ
- Different tissues organised to do a major job.
- Organ system
- Several organs working together for a major function.
- Multicellular organism
- A living being made up of many cells.
- Microorganism
- A living thing too small to be seen with the naked eye.
- Decomposition
- Breaking down of dead matter by microbes into nutrient-rich substances.
- Manure
- Nutrient-rich material formed when microbes break down waste.
- Yeast
- A unicellular fungus that releases carbon dioxide, used to make dough rise.
- Fermentation
- The breakdown of sugar by microbes, used in making curd, idli, and dosa.
- Legumes
- Plants whose seeds grow in pods, such as peas, beans, and lentils.
- Rhizobium
- Bacteria in legume root nodules that trap nitrogen from the air.
- Microalgae
- Microscopic plant-like organisms that make food and release oxygen.
- Nucleoid
- The region in a bacterial cell holding genetic material, with no membrane.
