How to Use This Page
Solve each Samacheer Kalvi exercise question on your own first, then compare your answer with the solutions below. The Living World chapter covers the fundamental characteristics of life and the principles of classification — master these before moving to later chapters.
Key Concepts (Quick Recap)
Characteristics of Living Organisms
- Growth: Increase in number of cells or mass. Plants: indeterminate (throughout life). Animals: determinate (stops at maturity).
- Reproduction: Producing offspring. Not unique to living things (crystals can "grow" and "reproduce").
- Metabolism: Sum total of all chemical reactions (anabolism + catabolism). Occurs in all living organisms.
- Cellular Organisation: All living organisms are composed of cells. Most fundamental characteristic.
- Consciousness (Response to stimuli): Ability to sense and respond to environmental stimuli. Most obvious feature of living organisms.
- Homeostasis: Maintaining a stable internal environment.
Important Distinctions
- Living growth vs non-living growth: Living growth is from inside (cell division). Non-living growth is by accumulation (crystal growth).
- Reproduction: Not a defining characteristic — sterile organisms (mules) are still living.
- Metabolism and cellular organisation are more defining characteristics than growth or reproduction.
Taxonomic Hierarchy
Kingdom → Phylum → Class → Order → Family → Genus → Species
Remember: King Philip Came Over For Good Soup
Binomial Nomenclature
- Introduced by Carl Linnaeus (Father of Taxonomy)
- Two-word system: Genus (capitalised) + species (lowercase)
- Written in italics (or underlined when handwritten)
- Example: Homo sapiens (human), Panthera leo (lion)
- Governed by ICZN (International Code of Zoological Nomenclature)
Five Kingdom Classification (Whittaker)
| Kingdom | Cell Type | Cell Wall | Nutrition | Organisation | Examples |
|---|
| Monera | Prokaryotic | Present (peptidoglycan) | Autotrophic/Heterotrophic | Unicellular | Bacteria, Cyanobacteria |
| Protista | Eukaryotic | Present/Absent | Autotrophic/Heterotrophic | Unicellular | Amoeba, Paramecium, Euglena |
| Fungi | Eukaryotic | Present (chitin) | Heterotrophic (saprophytic) | Multicellular/Unicellular | Mushroom, Yeast, Aspergillus |
| Plantae | Eukaryotic | Present (cellulose) | Autotrophic (photosynthesis) | Multicellular | Mango, Fern, Moss |
| Animalia | Eukaryotic | Absent | Heterotrophic (holozoic) | Multicellular | Human, Fish, Insect |
Taxonomical Aids
- Herbarium: Dried, pressed, preserved plant specimens with labels
- Museum: Preserved plant and animal specimens (wet/dry preservation)
- Botanical Garden: Living collection of plants for study (e.g., Kew Gardens)
- Zoological Park (Zoo): Living animals in protected environments
- Key: Analytical device using contrasting characters (couplets) for identification
- Flora: Book describing all plant species in a region
- Manual: Book for identification of species in a region
- Monograph: Detailed study of a single taxon
I. Choose the Best Answer (MCQs)
Q1. The most fundamental characteristic of living organisms is (a) Growth (b) Reproduction (c) Cellular organisation (d) Movement
Answer(c) Cellular organisation — All living organisms are composed of cells. Cellular organisation is the most fundamental characteristic because even unicellular organisms (bacteria, amoeba) have cellular organisation, and it is the basis of all life processes.
Q2. Binomial nomenclature was introduced by (a) Charles Darwin (b) Carolus Linnaeus (c) Aristotle (d) Robert Whittaker
Answer(b) Carolus Linnaeus — Carl Linnaeus (Carolus Linnaeus) introduced the binomial nomenclature system of naming organisms with two words — Genus + species.
Q3. In binomial nomenclature, the first word represents (a) Species (b) Genus (c) Family (d) Order
Answer(b) Genus — In binomial nomenclature, the first word is the genus name (always capitalised) and the second word is the species epithet (always lowercase). Example: Homo (genus) sapiens (species).
Q4. The five kingdom classification was proposed by (a) Linnaeus (b) Whittaker (c) Copeland (d) Haeckel
Answer(b) Whittaker — R.H. Whittaker proposed the five kingdom classification (Monera, Protista, Fungi, Plantae, Animalia) in 1969 based on cell type, cell wall, mode of nutrition, and body organisation.
Q5. Which kingdom includes organisms without a cell wall? (a) Monera (b) Protista (c) Fungi (d) Animalia
Answer(d) Animalia — Organisms in Kingdom Animalia are eukaryotic, multicellular, heterotrophic, and lack a cell wall. This distinguishes them from Plantae (cellulose cell wall), Fungi (chitin cell wall), and Monera (peptidoglycan cell wall).
Q6. A herbarium is a collection of (a) Living plants (b) Living animals (c) Dried, pressed plant specimens (d) Preserved animal specimens
Answer(c) Dried, pressed plant specimens — A herbarium is a collection of dried, pressed, and preserved plant specimens mounted on sheets with labels showing name, collector, date, and location.
Q7. The basic unit of classification is (a) Genus (b) Family (c) Species (d) Order
Answer(c) Species — Species is the basic unit of classification. Members of the same species can interbreed and produce fertile offspring.
II. Fill in the Blanks
1. The two-word naming system is called binomial nomenclature. 2. The first word in a scientific name represents the genus. 3. The second word in a scientific name represents the species epithet (specific epithet). 4. Scientific names are printed in italics (or underlined when handwritten). 5. The basic unit of classification is species. 6. The five kingdoms are Monera, Protista, Fungi, Plantae, and Animalia. 7. Organisms in Kingdom Animalia lack a cell wall. 8. Organisms in Kingdom Fungi have a cell wall made of chitin. 9. Linnaeus is called the Father of Taxonomy. 10. A herbarium is a collection of dried, pressed plant specimens. 11. The taxonomic hierarchy from broadest to most specific is Kingdom → Phylum → Class → Order → Family → Genus → Species. 12. Kingdom Monera includes prokaryotic organisms (bacteria and cyanobacteria).
III. True or False (with corrections for false statements)
Q1. Reproduction is the defining characteristic of living organisms.
AnswerFalse — Correction: Reproduction is NOT the sole defining characteristic because (1) sterile organisms like mules are living but cannot reproduce, (2) non-living things like crystals can "reproduce." Cellular organisation and metabolism are more defining.
Q2. In binomial nomenclature, both words begin with capital letters.
AnswerFalse — Correction: Only the FIRST word (genus) begins with a capital letter. The SECOND word (species epithet) always begins with a lowercase letter. Example: Homo sapiens, not Homo Sapiens.
Q3. Members of the same species can interbreed and produce fertile offspring.
AnswerTrue — Species is defined as a group of organisms that can interbreed among themselves and produce fertile offspring, but are reproductively isolated from other such groups.
Q4. Kingdom Animalia includes organisms with a cell wall.
AnswerFalse — Correction: Kingdom Animalia includes organisms that lack a cell wall. Plantae has cellulose cell walls, Fungi has chitin cell walls, and Monera has peptidoglycan cell walls.
Q5. Growth in plants is determinate.
AnswerFalse — Correction: Growth in plants is indeterminate — it continues throughout the plant's life through cell division in meristematic tissues. Growth in animals is determinate — it stops at maturity.
IV. Match the Following
| Column A | Column B | Answer |
|---|
| 1. Kingdom Monera | (a) Eukaryotic, cell wall absent | (b) Prokaryotic, peptidoglycan cell wall |
| 2. Kingdom Protista | (b) Prokaryotic, peptidoglycan cell wall | (c) Eukaryotic, unicellular |
| 3. Kingdom Fungi | (c) Eukaryotic, unicellular | (d) Eukaryotic, chitin cell wall |
| 4. Kingdom Plantae | (d) Eukaryotic, chitin cell wall | (e) Eukaryotic, cellulose cell wall |
| 5. Kingdom Animalia | (e) Eukaryotic, cellulose cell wall | (a) Eukaryotic, cell wall absent |
V. Answer Briefly (2-mark questions)
Q1. What are the defining characteristics of living organisms?
Answer
The defining characteristics of living organisms are: 1. Growth: Increase in cell number or mass 2. Reproduction: Production of offspring 3. Metabolism: Sum total of all chemical reactions (anabolism + catabolism) 4. Cellular organisation: All living organisms are made of cells 5. Consciousness: Ability to sense and respond to stimuli 6. Homeostasis: Maintenance of stable internal environment
Q2. What is binomial nomenclature? Give two rules.
Answer
Binomial nomenclature is a two-word naming system for organisms developed by Carl Linnaeus. Each organism has a scientific name with two words — the first is the genus (capitalised) and the second is the species epithet (lowercase). Rules: (1) Scientific names are in Latin and printed in italics (underlined when handwritten). (2) The genus name starts with a capital letter and the species name starts with a lowercase letter. Example: Homo sapiens.
Q3. Distinguish between Kingdom Monera and Kingdom Protista.
Answer
| Feature | Kingdom Monera | Kingdom Protista | |---|---|---| | Cell type | Prokaryotic | Eukaryotic | | Cell wall | Present (peptidoglycan) | Present or absent | | Organisation | Unicellular | Mostly unicellular | | Nutrition | Autotrophic or heterotrophic | Autotrophic or heterotrophic | | Examples | Bacteria, Cyanobacteria | Amoeba, Paramecium, Euglena |
Q4. What is a herbarium? What information does a herbarium sheet contain?
Answer
A herbarium is a collection of dried, pressed, and preserved plant specimens mounted on sheets. Each herbarium sheet contains: 1. Scientific name of the plant 2. Name of the collector 3. Date of collection 4. Place of collection (locality) 5. Name of the family 6. Sometimes, local/vernacular name
VI. Answer in Detail (5-mark questions)
Q1. Explain the five kingdom classification with characteristics and examples.
Answer
1. Kingdom Monera: - Prokaryotic, unicellular organisms - Cell wall present (peptidoglycan) - Nutrition: Autotrophic (photosynthetic bacteria) or heterotrophic - Examples: Bacteria (E. coli, Streptococcus), Cyanobacteria (Nostoc, Anabaena) 2. Kingdom Protista: - Eukaryotic, mostly unicellular organisms - Cell wall may or may not be present - Nutrition: Autotrophic (Euglena) or heterotrophic (Amoeba) - Locomotion: Pseudopodia (Amoeba), cilia (Paramecium), flagella (Euglena) - Examples: Amoeba, Paramecium, Euglena, Plasmodium 3. Kingdom Fungi: - Eukaryotic, multicellular or unicellular - Cell wall present (chitin) - Nutrition: Heterotrophic (saprophytic — absorb nutrients from dead matter) - Reproduction: Asexual (spores, budding) and sexual - Examples: Mushroom, Yeast, Aspergillus, Rhizopus (bread mould) 4. Kingdom Plantae: - Eukaryotic, multicellular organisms - Cell wall present (cellulose) - Nutrition: Autotrophic (photosynthesis) - Reproduction: Asexual and sexual - Divisions: Algae, Bryophytes, Pteridophytes, Gymnosperms, Angiosperms - Examples: Mango, Fern, Moss, Pinus, Rose 5. Kingdom Animalia: - Eukaryotic, multicellular organisms - Cell wall absent - Nutrition: Heterotrophic (holozoic — ingest food) - Reproduction: Mostly sexual - Locomotion: Most can move - Examples: Human, Fish, Insect, Bird, Reptile
Q2. Explain the taxonomic hierarchy with an example.
Answer
The taxonomic hierarchy is a system of classification where organisms are arranged in ranks from the broadest (Kingdom) to the most specific (Species). Taxonomic Hierarchy (broadest → most specific): 1. Kingdom: Broadest category. E.g., Animalia (all animals) 2. Phylum: Groups of related classes. E.g., Chordata (animals with notochord) 3. Class: Groups of related orders. E.g., Mammalia (mammals) 4. Order: Groups of related families. E.g., Primates 5. Family: Groups of related genera. E.g., Hominidae (great apes) 6. Genus: Groups of related species. E.g., Homo 7. Species: Basic unit — organisms that can interbreed. E.g., sapiens Example — Human (Homo sapiens): Kingdom: Animalia → Phylum: Chordata → Class: Mammalia → Order: Primates → Family: Hominidae → Genus: Homo → Species: sapiens
Q3. What are taxonomical aids? Explain any four.
Answer
Taxonomical aids are collections, tools, and techniques used for the identification, classification, and study of organisms. 1. Herbarium: A collection of dried, pressed, and preserved plant specimens mounted on sheets with labels showing name, collector, date, and location. It serves as a reference for identification and research. The largest herbarium in the world is at the Royal Botanic Gardens, Kew (London). 2. Museum: A collection of preserved plant and animal specimens for study and reference. Specimens may be preserved in jars (wet preservation — formalin) or as dry specimens (insects pinned, skeletons). Museums provide a permanent record of biodiversity. 3. Zoological Park (Zoo): A place where live animals are kept in protected environments resembling their natural habitats. Zoos help in conservation, education, and research. Animals are labelled with their scientific names, diet, and habitat. 4. Key: An analytical device used for the identification of organisms based on contrasting characters. A key consists of couplets — each couplet offers two contrasting choices, and the user follows the matching choice to identify the organism. Keys can be bracketed (indented) or numbered.
Common Mistakes to Avoid
- Capitalising the species epithet: In Homo sapiens, only the genus (Homo) is capitalised. The species (sapiens) is always lowercase.
- Not italicising scientific names: Scientific names must be in italics when printed (or underlined when handwritten).
- Confusing Kingdom Monera and Protista: Monera = prokaryotic (no nucleus). Protista = eukaryotic (with nucleus). This is the key distinction.
- Saying animals have a cell wall: Kingdom Animalia organisms LACK a cell wall. Only Plantae (cellulose), Fungi (chitin), and Monera (peptidoglycan) have cell walls.
- Calling reproduction the defining characteristic: Reproduction is important but NOT the sole defining characteristic. Sterile organisms (mules) are living but cannot reproduce.
- Confusing herbarium and botanical garden: Herbarium = dried, pressed plant specimens. Botanical garden = living plants.
- Reversing the taxonomic hierarchy: Kingdom → Phylum → Class → Order → Family → Genus → Species. Remember: King Philip Came Over For Good Soup.
Exam Checklist
- [ ] Can you list the characteristics of living organisms and explain why no single one is the defining feature?
- [ ] Can you explain binomial nomenclature with its rules and examples?
- [ ] Can you write the taxonomic hierarchy in correct order?
- [ ] Can you classify an organism (e.g., human, tiger, mango) through all taxonomic ranks?
- [ ] Can you explain the five kingdom classification with characteristics and examples?
- [ ] Can you distinguish between Monera, Protista, Fungi, Plantae, and Animalia?
- [ ] Can you define species, genus, family, order, class, phylum, and kingdom?
- [ ] Can you explain what a herbarium is and what information it contains?
- [ ] Can you distinguish between herbarium, museum, botanical garden, zoo, and key?
- [ ] Can you give at least 4 rules of binomial nomenclature with examples?
