Classification of Living Beings

Chapter 2-Classification of living beings

Living organisms on Earth are incredibly diverse, ranging from tiny microscopic bacteria to giant whales and tall trees. To study them systematically, scientists classify living beings into groups based on their similarities and in structures, nutrition, cell types, and other characteristics. This is called classification.

The widely accepted system divides living organisms into five kingdoms: Monera, Protista, Fungi, Plantae, and Animalia. Each kingdom groups organisms with features, making it easier to study their relationships and evolutionary.

Five Kingdom Classification

• Organ are classified by structure, nutrition, cell type, presence/absence of cell wall, etc.
• Robert Whittaker classified living beings into Five Kingdoms:
  1. Monera - Prokaryotic organisms (e.g., Bacteria)
  2. Protista - Unicellular eukaryotes (e.g., Euglena)
  3. F - Saprotrophic with cell wall, chlorophyll (e.g., Mushroom) 4 Plantae - Autotroph with cellulose cell wall (e.g., Fern)
  4. Animalia - Multic heterotrophs with no cell wall (e.g., Frog)

2. Kingdom Plantae

• Organisms with chlorophyll, autotrophic, cell wall made of cellulose.
• Divided into 3 divisions

A. Algae (Division Algae)

• Simple plants; thallus body (no root, stem, leaf differentiation)
• Can be unicellular or multicellular
• Reproduce sexually & asexually
• Found in water/marshy places
• Examples: Spirogyra, Volvox,ucus

B. Bryophyta (Mosses)

• More developed than algae
• Body parts: Rhizoid, stem, simple leaf
• Found in moist, shady places
• Depend on water for fertilization (amphibian plant)
• Gametophy stage dominant
• No vascular tissue (no xylem, phloem)
• Examples: Marchantia, Moss,cia

C. TracheophytaVascular Plants)

• Have true root, stem, leaves
• Have vascular tissue (xylem & phloem)

Subdivisions of Tracheophyta:

1. Pteridophyta (Ferns and allies)
   • No flowers or seeds
   • Have spores, sori on
   • Example: Fern, club moss, horsetail
2. Gymnosperms
   • Bear cones, seeds naked (no fruit)
   • Needle-like leaves
   • Example: Cycas, Pinus, Juniper
3. Angiosperms (Flowering plants)
   • Seeds enclosed in fruit
   • Have flowers, well-developed roots & stems
   • Divided into:
     • Monocotyledons: parallel vein leaves, fibrous roots, floral parts in 3s (e.g. Maize, Banana)
     • Dicotyledons: net-veined leaves,root system, floral parts in 4 or 5s (e.g. Mustard, Pea)

3. Kingdom Animalia

• Multicellular, eukaryotic,otrophic, no cell wall.
• Divided into based on body structure and complexity.
• Two types:
  • Invertebrates – No backbone
  • Vertebrates Have backbone (vertebral column)

Invertebrates Phyla Examples:

• Porifera: Sponges - multicellular, with pores (e.g., Spongilla)
• Coelenterata: Radial symmetry, tentacles (e.g., Hydra, Jellyfish)
• Platyhelminthes: Flatworms,itic (e.g., Tapeworm)
• Nemathelminthes Roundworms, parasites (e.g Ascaris)
• Annelida: Segmented worms (e.g., Earthworm, Leech)
• Arthropoda: Joint-legged with exoskeleton (e.g., Butterfly, Crab)
• Mollusca: Soft-bodied, often with shells (e.g Snail, Octopus)
• Echinodermata: Spiny skin, radial symmetry (e.g., Starfish)

Vertebrates (Phylum Chordata):

• Have vertebral column
• Divided into 5 classes:

1. Pisces (Fish)
   • Gills for respiration
   • Two-chambered heart
   • Scaly, streamlined body2. Amphibia
   • skin, live both in water & land --chambered heart
   • Young have gills, adults lungs & skin breathe
2. Reptilia
   • Dry scaly skin
   • Three-chambered (except crocodile has four)
   • Lay eggs (oviparous)
3. Aves (Birds)
   • Feathers, wings for flying
   • Four-chambered heart
   • Homeothermic (constant body temperature)
4. Mammalia
   • Hair on body
   • Mammary glands (produce milk)
   • Four-chambered heart, homeothermic
   • Viviparous (give birth to live young)

4. Evolution and Classification

• Prokaryotes (Monera) evolved first.
• Then unicellular eukaryotes (ista).
• Multicellular evolved with fungi, plants, and animals.
• Organisms are classified based on similarities and differences—show common ancestry.
• Evolution shows gradual development from simple to complex organisms.

5. Important Concepts

• Alternation of Generation (in plants like moss and fern): life cycle alternates gametophyte and sporophyte stages.
• Bacteria vs Euglena: Bacteria are prokaryotes; Euglena is a unicellularist with chlorophyll.
• Ferns vs Mushrooms: Ferns have chlorophyll and vascular tissue, mushrooms do not and are saprotrophic.
• Animals classification: Vertebrates (with backbone and Invertebrates (without backbone).
• Animals differ in types of respiratory organs, body covering, reproduction, and symmetry.