Diversity in Living Organisms
Contents
- Biodiversity & Classification
- Taxonomy & Linnaeus
- Hierarchy of Classification
- Five Kingdom Classification
- Kingdom Monera
- Kingdom Protista
- Kingdom Fungi
- Kingdom Plantae
- Kingdom Animalia
- Vertebrata – Classes
- Binomial Nomenclature
Biodiversity & Classification
Biodiversity means different forms of living organisms or a variety of life forms found in a particular region. The branch of science dealing with identification, naming and classification of organisms is called systematics or taxonomy.
Classification enables us to study organisms conveniently, reveals inter-relationships between groups, and helps establish evolutionary tendencies.
Artificial vs. Natural Classification
- Artificial classification (Aristotle) — based on one or few arbitrarily chosen criteria (habitat, habit). Drawback: grouped unrelated organisms; separated related ones.
- Natural classification — based on multiple characters, from broad groups down to smallest units, reflecting true evolutionary relationships.
- Phylogenetic classification — based on evolutionary relationships of organisms.
Taxonomy & Carolus Linnaeus
Carolus Linnaeus (1707–1778), a Swedish scientist, is called the father of Taxonomy. He introduced binomial nomenclature and published Systema Naturae (1735), classifying all known organisms.
History of Kingdom Classifications
| Classification | Proposed By | Kingdoms |
|---|---|---|
| Two Kingdom | Carolus Linnaeus, 1758 | Plantae, Animalia |
| Three Kingdom | Ernst Haeckel | + Protista |
| Four Kingdom | Copeland | + Monera |
| Five Kingdom | R.H. Whittaker, 1969 | Monera, Protista, Fungi, Plantae, Animalia |
Hierarchy of Classification (Linnaean)
| Category | Description & Example |
|---|---|
| Species | Lowest; individuals that can interbreed. Pisum sativum (pea). |
| Genus | Closely related species. Dog & wolf → Canis. |
| Family | Related genera. Cat & lion → Felidae. |
| Order | Assemblage of families with common characters. |
| Class | Related orders. Rats, camels, monkeys → Chordata. |
| Phylum/Division | Classes with same specific characters. |
| Kingdom | Highest category — Plantae, Animalia. |
Five Kingdom Classification (Whittaker, 1969)
| Kingdom | Organisation | Prokaryotic/Eukaryotic | Cell Wall | Nutrition |
|---|---|---|---|---|
| Monera | Unicellular | Prokaryotic | Some have, some don't | Autotrophic & Heterotrophic |
| Protista | Unicellular | Eukaryotic | Some have, some don't | Autotrophic & Heterotrophic |
| Fungi | Multicellular | Eukaryotic | Chitin | Heterotrophic |
| Plantae | Multicellular | Eukaryotic | Cellulose | Autotrophic |
| Animalia | Multicellular | Eukaryotic | Absent | Heterotrophic |
Check Out- CBSE Class 9 Science Notes
Kingdom Monera
- Mostly unicellular; cyanobacteria are filamentous.
- No definite nucleus — circular dsDNA not enclosed by nuclear envelope (prokaryotes).
- No membrane-bound organelles (except ribosomes).
- Cell wall generally present; single-stranded flagella in many.
- Nutrition: autotrophic or heterotrophic.
Groups within Monera
- True bacteria: Cocci, Diplococci, Bacilli, Spirilli, Vibrio.
- Actinomycetes: Unicellular, branched, filamentous — Streptomycetes, Mycobacterium.
- Cyanobacteria (Blue-green algae): Nostoc, Anabaena (N₂ fixation), Oscillatoria, Trichodesmium (red colour of sea).
- Mycoplasma: Mycoplasma pneumoniae.
- Archaebacteria: Methanogens, Halophiles, Thermoacidophiles.
Kingdom Protista
- Mostly aquatic; typically eukaryotic with distinct plasma membrane.
- Contain membrane-bound organelles (mitochondria, plastids, Golgi, ER, ribosomes).
- DNA: linear dsDNA complexed with proteins in chromosomes; nucleolus present.
- Motile forms use pseudopodia, flagella or cilia.
Three Major Groups
- Protistan algae (plant-like): Dinoflagellates, Diatoms, Euglena, Chlamydomonas, Volvox.
- Protozoa (animal-like): Amoeba, Entamoeba, Paramecium, Trypanosoma, Plasmodium.
- Slime moulds (fungus-like): Physarum, Dictyostelium.
Kingdom Fungi
- Thalloid, unicellular or multicellular, filamentous/mycelial. Single filament = hypha; cluster = mycelium.
- Cell wall of chitin (tough complex sugar).
- Lack chlorophyll — heterotrophic (saprotrophic or parasitic).
- Reserve food: glycogen and oil drops.
- Asexual reproduction by spores; sexual by gamete fusion.
Examples: Yeast (Saccharomyces), mushroom (Agaricus campestris), Rhizopus, Penicillium, Aspergillus.
Kingdom Plantae
Multicellular eukaryotes with chlorophyll for photosynthesis. Cell wall of cellulose; large central vacuole; mostly non-motile; indefinite growth.
Division: Thallophyta
Most primitive plants; no differentiation into root, stem, leaves (thalloid). Predominantly aquatic; no vascular system; single-celled reproductive organs.
- Algae: Aquatic or terrestrial; autotrophic; unicellular to multicellular. Examples: Nostoc, Anabaena, Ulothrix, Spirogyra, Ulva, Chara.
- Fungi (within Thallophyta): Heterotrophic; chitin cell wall; parasitic or saprotrophic. Examples: Rhizopus, Saccharomyces, Agaricus, Aspergillus, Penicillium.
- Lichens: Symbiotic relationship between algae (phycobiont) and fungi (mycobiont). Grow on rocks, tree trunks. Examples: Parmelia, Alectoria.
Division: Bryophyta
Simplest non-vascular land plants; amphibians of the plant kingdom (need water for life cycle). Main plant body is gametophyte (haploid). No xylem/phloem.
Examples: Funaria (moss), Riccia, Marchantia.
Division: Pteridophyta (First Vascular Plants)
Sporophyte (diploid); true roots, stem, leaves; xylem and phloem present. Flowers and seeds absent. Male sex organs: antheridia; female: archegonia.
Examples: Lycopodium, Selaginella, Equisetum, Marsilea, Azolla, Pteridium (fern).
| Feature | Bryophytes | Pteridophytes |
|---|---|---|
| Plant body | Gametophyte (haploid) | Sporophyte (diploid) |
| Differentiation | Thallus/foliose; no true roots, stem, leaves | True roots, stem and leaves |
| Attachment | Rhizoids | True roots |
| Vascular tissue | Absent | Present |
Division: Gymnosperms
Vascular, perennial, evergreen, woody plants. Ovules are naked (not enclosed in ovaries). After fertilisation, ovules become seeds (not enclosed in fruits). Sporophylls form cones (separate male and female).
Examples: Cycas, Pinus, Ephedra.
Division: Angiosperms (Flowering Plants)
Seeds enclosed within fruits (developed from ovary). Embryo has plumule, radicle and cotyledons. Two sub-groups based on number of cotyledons:
| Feature | Dicotyledons | Monocotyledons |
|---|---|---|
| Cotyledons | Two | One |
| Leaf venation | Reticulate | Parallel |
| Vascular bundle | Open, in a ring | Closed, scattered |
| Root system | Tap root | Fibrous |
| Flower parts | Pentamerous or tetramerous | Trimerous |
| Examples | Pea, Gram, Mustard | Wheat, Rice, Maize |
Kingdom Animalia – Non-Chordates
Multicellular, eukaryotic, no chlorophyll, no cell wall. Nutrition by ingestion. Reproduction mostly sexual. Growth stops at adult stage.
- Mostly marine; sessile; radial symmetry or asymmetrical.
- Cellular level of organisation (simplest multicellular animals; no tissues/organs).
- Body perforated by pores (Ostia); single opening = osculum; canal system.
- Hard outside skeleton of spicules; no mouth/digestive cavity/anus.
- Asexual by budding/gemmules; sexual by ova and spermatozoa.
- Aquatic; two-layered body (tissue level of organisation); radial symmetry.
- Single body cavity with one aperture (mouth); no anus.
- Stinging cells: cnidoblasts. Tentacles present.
- Both asexual and sexual reproduction.
- Marine, transparent, radial symmetry; 8 ciliated comb plates for locomotion.
- Bilaterally symmetrical; dorsoventrally flattened; no segmentation.
- First animals with 3 germ layers (triploblastic); no true coelom.
- Excretion by flame cells (protonephridia); mostly hermaphrodite.
- Cylindrical; bilaterally symmetrical; triploblastic; unsegmented; tough cuticle.
- Body cavity = pseudocoelom (not lined by mesoderm); straight one-way alimentary canal.
- Sexes generally separate; mostly parasitic.
- Soft, elongated, bilaterally symmetrical; body divided into metameres (segmentation = metamerism).
- Locomotory appendages: parapodia, setae/chaetae.
- True coelom; complete alimentary canal; closed circulatory system.
- Excretion by metanephridia.
Largest phylum (~900,000 species).
- Segmented body grouped into cephalothorax + abdomen, or head + thorax + abdomen (tagmatization).
- Exoskeleton of chitin; jointed legs; haemocoel (open circulatory system).
- Respiration by gills, trachea, or book-lungs.
- Soft, unsegmented; body in three regions: head, visceral mass, ventral foot.
- Mantle secretes calcareous shell; respiration by ctenidia (gills).
- Marine; radial symmetry in adults; no head; mesodermal exoskeleton of calcareous spines.
- True coelom; peculiar tube feet for locomotion; sexes separate.
Three distinctive characters present at some stage:
- Notochord — solid, unjointed rod (persists in lower chordates; replaced by vertebral column in higher ones).
- Dorsal hollow nerve cord
- Pharyngeal gill slits
Sub-Phylum Vertebrata – Five Classes
Class Cyclostomata (Agnatha)
Most primitive vertebrates; jawless; circular suctorial mouth; cartilagenous skeleton; two-chambered heart (1 auricle + 1 ventricle); external fertilisation.
Examples: Petromyzon (lamprey), Myxine (hagfish).
Class Pisces (Fish)
Exclusively aquatic; scales; respiration by gills; cold-blooded; two-chambered heart; external fertilisation.
| Feature | Chondrichthyes (Cartilaginous) | Osteichthyes (Bony) |
|---|---|---|
| Skeleton | Cartilaginous throughout | Bony in adult |
| Mouth | Ventral | Terminal |
| Tail fin | Heterocercal (asymmetric) | Homocercal (symmetric) |
| Gills covered? | No (naked) | Yes (operculum) |
| Swim bladder | Absent | Usually present |
| Fertilisation | Internal | External |
| Examples | Sharks, rays, Scoliodon | Labeo, Hippocampus, Anabas |
Class Amphibia
Live on land and water; first vertebrates to invade land; cold-blooded; smooth moist skin; two pairs of pentadactyl limbs; respiration by gills, lungs, skin and bucco-pharyngeal cavity; three-chambered heart (2 auricles + 1 ventricle); no marine forms.
Examples: Rana tigrina (frog), Bufo (toad), Hyla (tree frog), Salamandra.
Class Reptilia
First vertebrates fully adapted to dry land; cold-blooded; horny epidermal scales (keratin); internal fertilisation; cleidoic eggs with calcareous shells; heart incompletely four-chambered (2 auricles + partly divided ventricle); 12 pairs of cranial nerves.
Examples: Hemidactylus (wall lizard), Python, Naja (cobra), Testudo (tortoise), Crocodiles, Gavialis (gharial).
| Feature | Amphibia | Reptilia |
|---|---|---|
| Skin | Smooth and moist | Dry and cornified |
| Scales | Absent | Present |
| Claws | Absent | Present |
| Heart | 3-chambered | Incompletely 4-chambered |
| Fertilisation | External | Internal |
Class Aves (Birds)
Forelimbs modified into wings; feathers cover body; bony but spongy/light endoskeleton; beak present; teeth absent; respiration by lungs; four-chambered heart; warm-blooded.
Examples: Columba (pigeon), Struthio (ostrich), Pavo (peacock), Corvus (crow). Flightless birds: Ostrich (Africa), Rhea (S. America), Kiwi (New Zealand), Emu (Australia), Penguin.
Class Mammalia
Primarily terrestrial; hair covers body; mammary glands (milk production); mostly viviparous (except Platypus, Echidna — oviparous); lungs for respiration; four-chambered heart; warm-blooded; two pairs of pentadactyl limbs.
Examples: Macropus (kangaroo), bat, Rattus (rat), Felis (cat), Panthera (lion, tiger, leopard), Elephas (elephant), Balaena (whale), Macaca (monkey), Homo sapiens (human).
| Feature | Invertebrata | Vertebrata |
|---|---|---|
| Notochord | Absent | Present at some stage |
| Nerve cord | Solid and ventral | Hollow and dorsal |
| Heart position | Dorsal (if present) | Ventral |
| Vascular system | Open or closed | Closed |
| Haemoglobin | Dissolved in plasma (if present) | In red blood corpuscles |
| Pharyngeal gill slits | Absent | Present |
| Post-anal tail | Absent | Present |
Binomial Nomenclature
Proposed by Carolus Linnaeus (1753). Each organism receives two names: first = genus (capital letter), second = species (small letter). Governed by ICBN (plants) and ICZN (animals).
Conventions
- Genus name begins with a capital letter; species name begins with a small letter.
- Printed in italics; when handwritten, genus and species are underlined separately.
- Scientific names are based on Latin and accepted internationally.
| Organism | Scientific Name |
|---|---|
| Human | Homo sapiens |
| Common frog | Rana tigrina |
| Pea | Pisum sativum |
| Mango | Mangifera indica |
| Lion | Panthera leo |
| Wheat | Triticum vulgare |
| Rice | Oryza sativa |
FAQs for CBSE Class 9 Science Notes Diversity in Living Organisms
Classification helps scientists organize living organisms into groups based on similarities and differences. It makes identification and study easier. The chapter explains how classification helps understand relationships among organisms and simplifies the study of biodiversity..
The five-kingdom classification includes Monera, Protista, Fungi, Plantae, and Animalia. Each kingdom has unique characteristics based on cell structure, nutrition, and organization. Students learn how organisms are grouped and how classification has evolved over time.
Biodiversity refers to the variety of living organisms present on Earth. It is important because it maintains ecological balance and supports life. The chapter highlights the significance of preserving biodiversity and understanding the vast range of species found in different habitats