NEET BIOLOGY – CHAPTER 1
THE LIVING WORLD – HIGH YIELD REVISION NOTES
1. WHAT IS LIVING?
Living organisms show several characteristics that distinguish them from non-living things.
Important characteristics:
• Growth
• Reproduction
• Metabolism
• Cellular organisation
• Consciousness
2. GROWTH
Growth = Increase in mass and/or increase in the number of cells.
Examples:
• Child → Adult
• Seed → Plant
In living organisms, growth mainly occurs through cell division.
NEET POINT: Growth is NOT an exclusive characteristic of living organisms because non-living things can also
grow. For example, crystals can increase in size by accumulation of material on their surface.
3. REPRODUCTION
Reproduction = Production of new individuals of the same species.
A. Asexual reproduction: Only one parent is involved. (Examples: Amoeba, Yeast)
B. Sexual reproduction: Usually involves two parents. Involves formation and fusion of gametes. (Examples:
Humans, flowering plants)
NEET POINT: Reproduction is NOT an all-inclusive characteristic of living organisms. Examples: Mules, sterile
worker bees, and infertile human couples cannot reproduce. Therefore, it is not a defining feature of life.
, 4. METABOLISM ★
Metabolism = Sum total of all chemical reactions occurring in a living organism. It is a defining feature of life.
A. Anabolism: Building or synthesis reactions. (Example: Amino acids → Proteins)
B. Catabolism: Breakdown reactions. (Example: Glucose → Energy)
5. CELLULAR ORGANISATION
The cell is the basic structural and functional unit of life.
• Unicellular: Made up of one cell (e.g., Amoeba, Paramecium, bacteria).
• Multicellular: Made up of many cells (e.g., Humans, plants, animals).
Basic organisation Hierarchy: Cell → Tissue → Organ → Organ System → Organism
6. CONSCIOUSNESS ★
Consciousness = Ability of an organism to sense and respond to its surroundings. It is a defining property of
living organisms.
Examples:
• Plant grows towards light.
• Touch-me-not plant folds its leaves when touched.
• Human withdraws hand after touching a hot object.
Humans show self-consciousness because they can think, learn, remember, and communicate.
7. BIODIVERSITY
Biodiversity = Variety of living organisms present on Earth. Organisms differ in size, shape, structure, habitat,
nutrition, and reproduction. Because there are millions of organisms, scientists need a systematic method to
identify, name, and classify them through Taxonomy.
8. TAXONOMY ★
Taxonomy deals with three systematic steps:
1. Identification: Finding out which organism it is.
2. Nomenclature: Giving an organism a universal scientific name.
3. Classification: Grouping organisms based on similarities and differences.
THE LIVING WORLD – HIGH YIELD REVISION NOTES
1. WHAT IS LIVING?
Living organisms show several characteristics that distinguish them from non-living things.
Important characteristics:
• Growth
• Reproduction
• Metabolism
• Cellular organisation
• Consciousness
2. GROWTH
Growth = Increase in mass and/or increase in the number of cells.
Examples:
• Child → Adult
• Seed → Plant
In living organisms, growth mainly occurs through cell division.
NEET POINT: Growth is NOT an exclusive characteristic of living organisms because non-living things can also
grow. For example, crystals can increase in size by accumulation of material on their surface.
3. REPRODUCTION
Reproduction = Production of new individuals of the same species.
A. Asexual reproduction: Only one parent is involved. (Examples: Amoeba, Yeast)
B. Sexual reproduction: Usually involves two parents. Involves formation and fusion of gametes. (Examples:
Humans, flowering plants)
NEET POINT: Reproduction is NOT an all-inclusive characteristic of living organisms. Examples: Mules, sterile
worker bees, and infertile human couples cannot reproduce. Therefore, it is not a defining feature of life.
, 4. METABOLISM ★
Metabolism = Sum total of all chemical reactions occurring in a living organism. It is a defining feature of life.
A. Anabolism: Building or synthesis reactions. (Example: Amino acids → Proteins)
B. Catabolism: Breakdown reactions. (Example: Glucose → Energy)
5. CELLULAR ORGANISATION
The cell is the basic structural and functional unit of life.
• Unicellular: Made up of one cell (e.g., Amoeba, Paramecium, bacteria).
• Multicellular: Made up of many cells (e.g., Humans, plants, animals).
Basic organisation Hierarchy: Cell → Tissue → Organ → Organ System → Organism
6. CONSCIOUSNESS ★
Consciousness = Ability of an organism to sense and respond to its surroundings. It is a defining property of
living organisms.
Examples:
• Plant grows towards light.
• Touch-me-not plant folds its leaves when touched.
• Human withdraws hand after touching a hot object.
Humans show self-consciousness because they can think, learn, remember, and communicate.
7. BIODIVERSITY
Biodiversity = Variety of living organisms present on Earth. Organisms differ in size, shape, structure, habitat,
nutrition, and reproduction. Because there are millions of organisms, scientists need a systematic method to
identify, name, and classify them through Taxonomy.
8. TAXONOMY ★
Taxonomy deals with three systematic steps:
1. Identification: Finding out which organism it is.
2. Nomenclature: Giving an organism a universal scientific name.
3. Classification: Grouping organisms based on similarities and differences.
