How to Use This Page
Solve each Samacheer Kalvi exercise question on your own first, then compare your answer with the solutions below. Taxonomy and Systematic Botany covers classification systems, the species concept, taxonomical aids, and the Bentham & Hooker system — focus on comparing systems and understanding the hierarchy of classification.
Key Concepts (Quick Recap)
Taxonomy vs Systematics
| Feature | Taxonomy | Systematics |
|---|---|---|
| Definition | Science of classification, identification, nomenclature | Study of diversity and evolutionary relationships |
| Scope | Naming and grouping organisms | Taxonomy + phylogenetic relationships |
| Focus | Classifying into ranks | Understanding evolutionary history |
| Includes | Identification, classification, nomenclature | All of taxonomy + phylogeny |
Hierarchy of Classification (Taxonomic Categories)
Kingdom → Division (Phylum) → Class → Order → Family → Genus → Species
- Species: Fundamental unit; a group of organisms that can interbreed and produce fertile offspring
- Genus: A group of related species sharing common ancestry
- Family: A group of related genera (e.g., Solanaceae — Solanum, Datura, Petunia)
- Order: A group of related families (e.g., Polymoniales includes Solanaceae and Convolvulaceae)
- Class: A group of related orders
- Division/Phylum: A group of related classes
- Kingdom: Highest category (e.g., Plantae)
Classification Systems
| System | Proposed by | Basis | Merits | Demerits |
|---|---|---|---|---|
| Artificial | Linnaeus | One or few morphological characters (e.g., number of stamens) | Simple, easy to follow | Groups unrelated organisms; ignores natural relationships |
| Natural | Bentham & Hooker, de Candolle | Many natural characters (morphology, anatomy) | More natural grouping; practical for identification | Not phylogenetic; does not show evolutionary relationships |
| Phylogenetic | Engler & Prantl, Hutchinson, Takhtajan | Evolutionary relationships and common ancestry | Shows evolutionary trends; based on descent | Changes with new evidence; sometimes speculative |
Bentham and Hooker's Classification
1. Dicotyledons (Polypetalae, Gamopetalae, Monochlamydae) 2. Gymnosperms 3. Monocotyledons
- Published in Genera Plantarum (1862–1883)
- Based on natural affinities
- Classified 97,205 species of seed plants
- Three main groups:
Species Concept
- Biological species concept (Mayr): A group of interbreeding natural populations that are reproductively isolated from other such groups
- Typological species concept: Based on a type specimen; morphological similarity
- Species is the fundamental unit of classification
Taxonomical Aids
| Aid | Purpose | Key Feature |
|---|---|---|
| Herbarium | Store dried, pressed plant specimens | Arranged by classification system; label has collection details |
| Botanical Garden | Live collection of plants for study | Labelled with scientific names; e.g., Kew Gardens, NBRI Lucknow |
| Museum | Preserve specimens in jars/skeletons | Houses preserved plants and animals |
| Flora | Book describing plants of a region | Lists all plant species in an area with descriptions |
| Key | Tool for identification of organisms | Couplet-based (dichotomous key); leads to correct identification |
| Monograph | Detailed study of one taxon | Comprehensive account of a single genus or family |
| Catalogue | List of species in a collection | Alphabetical list with brief descriptions |
Important Botanical Gardens in India
- Indian Botanic Garden, Howrah (largest)
- Lal Bagh Botanical Garden, Bangalore
- National Botanical Research Institute (NBRI), Lucknow
- Government Botanical Garden, Ooty
I. Choose the Best Answer (MCQs)
Q1. The fundamental unit of classification is (a) Genus (b) Family (c) Species (d) Order
Q2. Bentham and Hooker's classification is an example of (a) Artificial system (b) Natural system (c) Phylogenetic system (d) Numerical system
Q3. A herbarium is a (a) Collection of live plants (b) Collection of dried, pressed plant specimens (c) Collection of animals (d) Collection of fossils
Q4. The taxonomic aid used for identification of organisms based on contrasting characters is (a) Herbarium (b) Key (c) Museum (d) Flora
Q5. Linnaeus' classification system is called artificial because (a) It uses many characters (b) It uses one or few morphological characters (c) It shows evolutionary relationships (d) It is based on molecular data
Q6. Which of the following is the correct taxonomic hierarchy? (a) Kingdom → Family → Order → Genus → Species (b) Kingdom → Order → Family → Genus → Species (c) Kingdom → Order → Genus → Family → Species (d) Kingdom → Genus → Order → Family → Species
Q7. Systematics differs from taxonomy in that it also includes (a) Identification (b) Nomenclature (c) Phylogenetic relationships (d) Classification
II. Fill in the Blanks
1. The branch of biology dealing with classification, identification, and nomenclature is called taxonomy. 2. The basic unit of classification is species. 3. Linnaeus proposed the artificial system of classification based on the number of stamens. 4. Bentham and Hooker proposed the natural system of classification. 5. A system of classification based on evolutionary relationships is called phylogenetic classification. 6. The preserved plant specimens in a herbarium are dried, pressed, and mounted. 7. A key is a taxonomical aid used for identification based on contrasting characters. 8. A flora is a book that lists and describes all plant species of a given region. 9. The largest botanical garden in India is the Indian Botanic Garden, Howrah. 10. The order of taxonomic categories from highest to lowest is Kingdom, Division, Class, Order, Family, Genus, Species. 11. A monograph gives a detailed account of a single taxon (genus or family). 12. The label on a herbarium sheet contains information about collection date, locality, collector's name, and habitat. 13. In Bentham and Hooker's system, seed plants are divided into Dicotyledons, Gymnosperms, and Monocotyledons. 14. Species that can interbreed and produce fertile offspring are called biological species. 15. The term 'Systematics' was coined by Linnaeus.
III. True or False (with corrections for false statements)
IV. Match the Following
| Column A | Column B | Answer |
|---|---|---|
| 1. Artificial classification | (a) Based on evolutionary relationships | (c) Based on one or few characters |
| 2. Natural classification | (b) Based on natural affinities | (b) Based on natural affinities |
| 3. Phylogenetic classification | (c) Based on one or few characters | (a) Based on evolutionary relationships |
| 4. Herbarium | (d) Detailed study of one taxon | (e) Dried, pressed plant specimens |
| 5. Monograph | (e) Dried, pressed plant specimens | (d) Detailed study of one taxon |
| 6. Flora | (f) Collection of live plants | (g) Book listing plants of a region |
V. Answer Briefly (2-mark questions)
VI. Answer in Detail (5-mark questions)
Common Mistakes to Avoid
- Confusing taxonomy and systematics: Taxonomy = classification + identification + nomenclature. Systematics = taxonomy + phylogenetic relationships. Systematics is the broader term.
- Calling Linnaeus' system natural or phylogenetic: Linnaeus' system is ARTIFICIAL — based on one character (number of stamens). Natural systems use many characters; phylogenetic systems use evolutionary relationships.
- Confusing herbarium and botanical garden: A herbarium stores DRIED, PRESSED specimens. A botanical garden has LIVE plants.
- Confusing monograph and flora: A monograph is a detailed study of one taxon (genus/family). A flora lists all plants of a region.
- Thinking species is not the fundamental unit: Species IS the fundamental unit. Kingdom is the highest, species is the lowest and most basic.
- Confusing artificial and natural classification merits: Artificial systems are simple but unnatural. Natural systems are more scientific but not phylogenetic.
- Forgetting that Bentham & Hooker's system is natural, not phylogenetic: This system is based on natural affinities, not evolutionary relationships.
Exam Checklist
- [ ] Can you differentiate taxonomy and systematics?
- [ ] Can you list the taxonomic hierarchy from Kingdom to Species?
- [ ] Can you describe the three types of classification systems with examples?
- [ ] Can you explain Bentham and Hooker's classification system?
- [ ] Can you define species and explain the biological species concept?
- [ ] Can you list and describe at least five taxonomical aids?
- [ ] Can you explain what a herbarium is and what a herbarium label contains?
- [ ] Can you distinguish between a key, a flora, and a monograph?
- [ ] Can you name important botanical gardens in India?
- [ ] Can you state the merits and demerits of each classification system?