Complete Biology notes on Plant and Animal Kingdom for BPSC and Other Competitive Exams in 2025

Complete Biology notes on Plant and Animal Kingdom for BPSC and Other Competitive Exams in 2025

General Science- 15 (Biology)

Plant and Animal Kingdom

The diversity of life on Earth is immense. To study and understand this vast variety, biologists classify organisms into different groups based on their similarities and differences. This systematic classification is known as Taxonomy.

1. Introduction to Biological Classification

• Why Classify
  • To organize the vast number of organisms into logical groups.
  • To understand the evolutionary relationships between different life forms.
  • To make the study of organisms easier and more systematic.
• Hierarchy of Classification (Taxonomic Ranks): Life is classified into a hierarchical system, from broad to specific:
  • Kingdom (Broadest)
  • Phylum (for animals) / Division (for plants)
  • Class
  • Order
  • Family
  • Genus
  • Species (Most specific, basic unit of classification)
• Binomial Nomenclature:
  • A two-part naming system for species, introduced by Carl Linnaeus.
  • Consists of the Genus name (capitalized) followed by the species name (lowercase). Both are italicized.
  • Example: Homo sapiens (for humans), Mangifera indica (for mango).
• Five Kingdom Classification (by R.H. Whittaker, 1969): This widely accepted system classifies all living organisms into five kingdoms based on cell structure, mode of nutrition, and body organization:

• Monera: Prokaryotic organisms (e.g., Bacteria).
• Protista: Unicellular eukaryotes (e.g., Amoeba, Paramecium).
• Fungi: Multicellular eukaryotes (mostly), heterotrophic (saprophytic or parasitic).
• Plantae: Multicellular eukaryotes, autotrophic (plants).
• Animalia: Multicellular eukaryotes, heterotrophic (animals).

2. Plant Kingdom (Plantae)

The Plant Kingdom includes all photosynthetic, multicellular, eukaryotic organisms with a cell wall made primarily of cellulose. They are autotrophs, meaning they produce their own food using photosynthesis.

General Characteristics of Plants:

• Multicellular: Composed of many cells.
• Eukaryotic: Possess a true nucleus and membrane-bound organelles.
• Autotrophic: Produce food through photosynthesis using chlorophyll.
• Cell Wall: Present, made of cellulose, providing structural support.
• Non-motile: Generally stationary (cannot move from one place to another).

Broad Classification of Plant Kingdom (based on increasing complexity):

1. Thallophytes (Algae):
   • Simplest plants: Body is not differentiated into roots, stems, and leaves (undifferentiated body is called a thallus).
   • Mostly aquatic (freshwater and marine).
   • Reproduce by spores.
   • Examples: Spirogyra, Ulothrix, Chlamydomonas.
2. Bryophytes (Mosses and Liverworts):
   • Often called the “Amphibians of the Plant Kingdom” because they live on land but require water for reproduction.
   • No true roots, stems, or leaves; have simple root-like structures called rhizoids.
   • Lack specialized vascular tissue (xylem and phloem) for water and nutrient transport.
   • Examples: Moss (Funaria), Liverwort (Marchantia).
3. Pteridophytes (Ferns and Horsetails):
   • The first terrestrial plants to possess true roots, stems, and leaves.
   • Possess vascular tissue (xylem and phloem) for efficient transport of water and nutrients.
   • Reproduce by spores (no seeds).
   • Examples: Ferns, Horsetails (Equisetum).
4. Gymnosperms:
   • “Naked seeds” – their seeds are not enclosed within a fruit.
   • Well-developed root, stem, and leaf systems.
   • Possess well-developed vascular tissue.
   • Often evergreen trees.
   • Examples: Pine, Cycas, Deodar, Sequoia.
5. Angiosperms (Flowering Plants):
   • The most diverse and dominant group of plants.
   • Characterized by the presence of flowers (reproductive organs).
   • Seeds are enclosed within a fruit.
   • Highly developed vascular tissue.
   • Sub-groups of Angiosperms:
     • Monocotyledons (Monocots):
       • Have a single cotyledon (seed leaf).
       • Leaves typically have parallel venation.
       • Usually have fibrous root systems.
       • Floral parts are often in multiples of three.
       • Examples: Rice, Wheat, Maize, Grasses, Lilies.
     • Dicotyledons (Dicots):
       • Leaves typically have reticulate (net-like) venation.
       • Usually have a tap root system.
       • Floral parts are often in multiples of four or five.
       • Examples: Pea, Bean, Mango, Rose, Sunflower.

3. Animal Kingdom (Animalia)

The Animal Kingdom includes all multicellular, eukaryotic organisms that are heterotrophic (obtain food by ingestion). They generally lack cell walls and are typically motile (can move).

General Characteristics of Animals:

• Multicellular: Composed of many cells that are organized into tissues, organs, and organ systems.
• Eukaryotic: Possess a true nucleus and membrane-bound organelles.
• Heterotrophic: Obtain nutrients by consuming other organisms.
• No Cell Wall: Animal cells lack a rigid cell wall.
• Motile: Most animals are capable of movement at some stage of their life cycle.
• Complex Organ Systems: Exhibit complex systems like nervous, muscular, and digestive systems.

Broad Classification of Animal Kingdom: The Animal Kingdom is broadly divided into two major groups: Invertebrates (animals without a backbone) and Vertebrates (animals with a backbone).

A. Invertebrates (Non-chordates – Animals without a backbone):

This group is highly diverse and includes the majority of animal species.

1. Phylum Porifera (Sponges):
   • Simplest multicellular animals.
   • Porous body (many pores for water circulation).
   • Sessile (immobile) aquatic animals.
   • Example: Sponges.
2. Phylum Coelenterata / Cnidaria (Jellyfish, Hydra, Corals):
   • Radially symmetrical.
   • Have a hollow body cavity (coelenteron).
   • Possess stinging cells (cnidoblasts/nematocysts) for defense and capturing prey.
   • Examples: Hydra, Jellyfish, Sea anemones, Corals.
3. Phylum Platyhelminthes (Flatworms):
   • Flattened, leaf-like or ribbon-like body.
   • Bilaterally symmetrical.
   • Often parasitic.
   • Examples: Tapeworm, Planaria, Liver Fluke.
4. Phylum Nematoda (Roundworms):
   • Cylindrical, unsegmented body.
   • Parasitic (e.g., Ascaris) or free-living.
   • Examples: Ascaris (roundworm), Filarial worm.
5. Phylum Annelida (Segmented Worms):
   • Body is segmented, both externally and internally.
   • True coelom (body cavity).
   • Examples: Earthworm, Leech, Nereis.
6. Phylum Arthropoda:
   • The largest phylum in the Animal Kingdom (includes insects, spiders, crustaceans).
   • Characterized by jointed appendages (legs) and an external skeleton (exoskeleton) made of chitin.
   • Segmented body.
   • Examples: Insects (Cockroach, Butterfly), Spiders, Crabs, Centipedes, Millipedes.
7. Phylum Mollusca:
   • Soft-bodied animals, often protected by a hard external shell (calcareous shell).
   • Have a muscular foot for movement.
   • Examples: Snails, Mussels, Oysters, Octopus, Squid.
8. Phylum Echinodermata:
   • Spiny-skinned animals.
   • Exclusively marine.
   • Radial symmetry in adults.
   • Possess a water-vascular system for locomotion and feeding.
   • Examples: Starfish, Sea Urchin, Sea Cucumber.

B. Vertebrates (Phylum Chordata – Animals with a backbone/vertebral column):

Chordates are characterized by the presence of a notochord (a flexible rod supporting the body), a dorsal hollow nerve cord, pharyngeal slits, and a post-anal tail at some stage of their development. Vertebrates are a subphylum of Chordata where the notochord is replaced by a bony or cartilaginous vertebral column (backbone).

1. Class Pisces (Fishes):
   • Aquatic animals.
   • Respire through gills.
   • Body covered with scales.
   • Possess fins for swimming.
   • Cold-blooded (poikilothermic) – body temperature varies with surroundings.
   • Lay eggs in water.
   • Examples: Shark, Rohu, Salmon.
2. Class Amphibia (Amphibians):
   • Can live both on land and in water.
   • Moist, glandular skin (no scales).
   • Respiration through skin, lungs, or gills (larval stage).
   • Cold-blooded.
   • Lay eggs in water.
   • Examples: Frogs, Toads, Salamanders.
3. Class Reptilia (Reptiles):
   • First truly terrestrial vertebrates.
   • Dry, scaly skin.
   • Respire through lungs.
   • Cold-blooded.
   • Lay hard-shelled eggs on land.
   • Examples: Snakes, Lizards, Crocodiles, Turtles.
4. Class Aves (Birds):
   • Body covered with feathers.
   • Forelimbs modified into wings for flight (most birds).
   • Possess a beak, no teeth.
   • Warm-blooded (homeothermic) – maintain a constant body temperature.
   • Lay hard-shelled eggs.
   • Examples: Pigeon, Sparrow, Ostrich.
5. Class Mammalia (Mammals):
   • Presence of mammary glands (females produce milk to nourish young).
   • Body covered with hair or fur.
   • Warm-blooded.
   • Most give live birth (viviparous), except for monotremes (e.g., Platypus, Echidna that lay eggs).
   • Possess external ears (pinnae).
   • Well-developed brain.
   • Examples: Humans, Cows, Dogs, Whales, Bats, Kangaroos.

Practice Questions

1. The scientific two-part naming system for organisms, consisting of genus and species, is known as:
   • A) Phylogeny
   • B) Binomial Nomenclature
   • C) Taxonomy
   • D) Classification Hierarchy
   • Rationale: Binomial nomenclature provides a unique and universal name for each species.
2. Which of the following is the broadest category in the hierarchical classification system of living organisms?
   • A) Class
   • B) Phylum
   • C) Species
   • D) Kingdom
   • Rationale: Kingdom is the highest and broadest taxonomic rank.
3. According to Whittaker’s Five Kingdom Classification, which kingdom includes organisms that are prokaryotic?
   • A) Protista
   • B) Fungi
   • C) Monera
   • D) Plantae
   • Rationale: The Kingdom Monera is exclusively for prokaryotic organisms like bacteria.

4. Which group of plants is often referred to as the “amphibians of the plant kingdom” due to their dependence on water for reproduction?
   • A) Thallophytes
   • B) Bryophytes
   • C) Pteridophytes
   • D) Angiosperms
   • Rationale: Bryophytes live on land but need water for fertilization.
5. Plants with “naked seeds” (seeds not enclosed within a fruit) belong to which group?
   • A) Pteridophytes
   • B) Gymnosperms
   • C) Angiosperms
   • D) Bryophytes
   • Rationale: Gymnosperms are characterized by their unenclosed seeds.
6. Which of the following is a characteristic feature of monocotyledonous plants?
   • A) Two cotyledons
   • B) Reticulate venation in leaves
   • C) Parallel venation in leaves
   • D) Tap root system
   • Rationale: Monocots typically have leaves with parallel veins.
7. The first group of terrestrial plants to possess a true vascular system (xylem and phloem) are:
   • A) Algae
   • B) Mosses
   • C) Ferns
   • D) Flowering plants
   • Rationale: Pteridophytes (like ferns) were the first land plants to evolve true vascular tissue.

8. Which phylum in the Animal Kingdom is characterized by jointed appendages and an exoskeleton, making it the largest phylum?
   • A) Mollusca
   • B) Annelida
   • C) Echinodermata
   • D) Arthropoda
   • Rationale: Arthropods, including insects and spiders, are defined by their jointed legs and chitinous exoskeleton.
9. Animals that are cold-blooded and lay hard-shelled eggs on land, typically having dry, scaly skin, belong to which class?
   • A) Amphibia
   • B) Pisces
   • C) Aves
   • D) Reptilia
   • Rationale: Reptiles are terrestrial, cold-blooded vertebrates with dry, scaly skin and lay amniotic eggs on land.
10. Which of the following is a distinguishing characteristic of mammals?
    • A) Respire through gills
    • B) Lay eggs (in all species)
    • C) Possess mammary glands
    • D) Are cold-blooded
    • Rationale: The presence of mammary glands for milk production is a unique and defining feature of mammals.
11. Starfish and sea urchins, known for their spiny skin and radial symmetry in adulthood, belong to which phylum?
    • A) Mollusca
    • B) Arthropoda
    • C) Coelenterata
    • D) Echinodermata
    • Rationale: Echinodermata means ‘spiny skin’, and these marine animals exhibit radial symmetry in their adult form.