Classification of Animals (Kingdom Animalia) – Complete Notes for Competitive Examinations

Home Academy Notes

(Useful for JKSSB, JKPSC, SSC, UPSC, CUET, NEET, State PSC, Forest Exams, Veterinary & Other Competitive Exams)

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Animal Classification (Taxonomy)

Classification is the scientific arrangement of animals into different groups based on their similarities, differences, body organization, embryonic development and evolutionary relationships.

Father of Animal Taxonomy

Aristotle – Father of Zoology

Carl Linnaeus – Father of Modern Taxonomy

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Taxonomic Hierarchy

Rank	Example (Human)
Kingdom	Animalia
Phylum	Chordata
Class	Mammalia
Order	Primates
Family	Hominidae
Genus	Homo
Species	Homo sapiens

Mnemonic

King Philip Came Over For Good Soup

(Kingdom → Phylum → Class → Order → Family → Genus → Species)

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Kingdom Animalia

General Characteristics

Multicellular organisms

Eukaryotic cells
Heterotrophic nutrition
Cell wall absent
Mostly motile
Reproduce sexually
Nervous system developed
Digestive system generally present

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Basis of Animal Classification
Animals are classified on the basis of:
Level of organization
Body symmetry
Germ layers
Body cavity (Coelom)
Segmentation
Presence or absence of notochord

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Level of Organization

Level	Animals
Cellular	Porifera
Tissue	Cnidaria
Organ	Platyhelminthes
Organ System	Nematoda onwards

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Body Symmetry
1. Asymmetrical
Cannot divide into equal halves.
Example
Sponge

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2. Radial Symmetry
Body divided into equal halves through many planes.
Examples
Hydra
Jellyfish
Sea Anemone
Starfish (adult)

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3. Bilateral Symmetry
Only one plane divides body equally.
Examples
Human
Earthworm
Cockroach
Fish

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Germ Layers
Diploblastic
Two germ layers
Ectoderm
Endoderm
Example
Hydra

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Triploblastic
Three germ layers
Ectoderm
Mesoderm
Endoderm
Examples
Earthworm
Human

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Body Cavity (Coelom)
Acoelomate
No body cavity
Example
Flatworm

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Pseudocoelomate
False body cavity
Example
Roundworm

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True Coelomate
True body cavity
Examples
Earthworm
Human

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Segmentation
Metamerism
Body divided into repeated segments.
Examples
Earthworm

Cockroach

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Notochord
Present only in chordates.
Examples
Fish
Frog
Birds
Human

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Classification of Animal Kingdom

Animal Kingdom

Animalia
│
├── Non-Chordata
│
│── Porifera
│── Cnidaria
│── Platyhelminthes
│── Nematoda
│── Annelida
│── Arthropoda
│── Mollusca
│── Echinodermata
│
└── Chordata

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NON-CHORDATES

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1. Phylum Porifera

Meaning

Pori = Pores

Characteristics

• Simplest multicellular animals

• Aquatic

• Mostly marine

• Cellular level organization

• Body full of pores

• Asymmetrical

• Skeleton of spicules

Examples

• Sycon

• Spongilla

• Euspongia

Important Facts

Oldest multicellular animals.

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2. Phylum Cnidaria (Coelenterata)

Characteristics

• Aquatic

• Radial symmetry

• Diploblastic

• Tentacles present

• Stinging cells (Cnidoblasts/Nematocysts)

Examples

• Hydra

• Jellyfish

• Sea Anemone

• Coral

Important

Coral reefs are formed by corals.

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3. Phylum Platyhelminthes

Flatworms

Characteristics

• Bilateral symmetry

• Triploblastic

• Acoelomate

• Flat body

Examples

• Tapeworm

• Liver fluke

• Planaria

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4. Phylum Nematoda (Aschelminthes)

Roundworms

Characteristics

Cylindrical body

Pseudocoelom
Bilateral symmetry
Examples
Ascaris
Wuchereria
Hookworm
Disease
Filariasis
Ascariasis

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5. Phylum Annelida
Segmented worms
Characteristics
True coelom
Segmented body
Closed circulatory system
Examples
Earthworm
Leech
Nereis

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6. Phylum Arthropoda
Largest phylum
Characteristics
Jointed legs
Chitin exoskeleton
Segmented body
Open circulatory system
Examples
Cockroach
Honey bee
Butterfly
Spider
Crab
Scorpion
Prawn
Important
Nearly 80% of known animal species belong to Arthropoda.

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7. Phylum Mollusca
Second largest phylum
Characteristics
Soft body
Shell generally present
Muscular foot
Examples
Snail
Octopus
Squid
Oyster
Important
Pearl is produced by Oyster.

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8. Phylum Echinodermata
Characteristics
Marine only
Spiny skin
Water vascular system
Adults radial
Larvae bilateral
Examples
Starfish
Sea Urchin
Sea Cucumber

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CHORDATA
Characteristics
Notochord present
Dorsal hollow nerve cord
Pharyngeal gill slits
Post-anal tail
Closed circulatory system

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Classification of Chordata
1. Pisces (Fishes)
Characteristics
Aquatic
Gills
Fins
Cold-blooded
Heart two-chambered
Examples
Rohu
Shark
Tuna

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2. Amphibia
Characteristics
Live on land and water
Moist skin
Larvae aquatic
Adults terrestrial
Heart three-chambered
Examples
Frog

Toad

Salamander

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3. Reptilia

Characteristics

Dry scales

Cold-blooded
Internal fertilization
Heart
Mostly 3 chambers
Crocodile → 4 chambers
Examples
Snake
Lizard
Crocodile
Turtle

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4. Aves (Birds)
Characteristics
Feathers
Wings
Warm-blooded
Four-chambered heart
Oviparous
Examples
Sparrow
Pigeon
Peacock
Eagle

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5. Mammalia
Characteristics
Mammary glands
Hair present
Warm-blooded
Four-chambered heart
Mostly viviparous
Examples
Human
Dog
Whale
Bat
Important

Bat is the only true flying mammal.

Whale is the largest mammal.

Blue Whale is the largest animal on Earth.

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Non-Chordates vs Chordates

Feature	Non-Chordates	Chordates
Notochord	Absent	Present
Nerve cord	Ventral	Dorsal
Heart	Usually dorsal	Ventral
Circulation	Mostly open	Closed (generally)

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Largest and Smallest (Exam Facts)

Feature	Answer
Largest Phylum	Arthropoda
Second Largest	Mollusca
Simplest Animal	Sponge
Largest Mammal	Blue Whale
Largest Bird	Ostrich
Largest Reptile	Saltwater Crocodile
Largest Fish	Whale Shark
Only Flying Mammal	Bat
Largest Animal	Blue Whale

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One-Liner Facts

Porifera have pores.
Cnidaria possess stinging cells.
Arthropoda have jointed legs.
Mollusca have muscular foot.
Echinoderms possess water vascular system.
Chordates possess notochord.
Earthworm has closed circulation.
Cockroach has open circulation.
Starfish can regenerate lost arms.
Crocodile has four-chambered heart.
Birds are warm-blooded.
Mammals possess mammary glands.

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Important MCQs

1. Largest phylum of Animal Kingdom is

A. Mollusca

B. Arthropoda ✅

C. Chordata

D. Porifera

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2. Which animal has pores?

A. Hydra

B. Sponge ✅

C. Earthworm

D. Starfish

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3. Water vascular system is found in

A. Mollusca

B. Arthropoda

C. Echinodermata ✅

D. Annelida

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4. Which animal possesses jointed appendages?

A. Cockroach ✅

B. Earthworm

C. Snail

D. Hydra

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5. Which is the only flying mammal?

A. Flying squirrel

B. Bat ✅

C. Eagle

D. Pigeon

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6. Heart with four chambers is present in

A. Frog

B. Lizard

C. Crocodile ✅

D. Snake

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7. Which phylum includes earthworm?

A. Arthropoda

B. Mollusca

C. Annelida ✅

D. Nematoda

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8. Which is the largest fish?

A. Blue Whale

B. Dolphin

C. Whale Shark ✅

D. Shark

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9. Notochord is present in

A. Arthropoda

B. Mollusca

C. Chordata ✅

D. Porifera

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10. Which animal forms coral reefs?

A. Hydra

B. Coral polyps ✅

C. Jellyfish

D. Starfish

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Statement-Based MCQs

Q1

Consider the following statements:

1. Arthropoda is the largest animal phylum.

2. Mollusca is the second largest phylum.

3. Porifera possess true tissues.

Options:

A. 1 only

B. 1 and 2 only ✅

C. 2 and 3 only

D. All are correct

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Q2

Consider the following statements:

1. Earthworm has a closed circulatory system.

2. Cockroach has an open circulatory system.

3. Starfish belongs to Arthropoda.

Answer:

A. 1 only

B. 1 and 2 only ✅

C. 2 and 3 only

D. All correct

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Q3

Which statements are correct?

1. Hydra is diploblastic.

2. Flatworms are acoelomate.

3. Roundworms are pseudocoelomate.

Answer:

A. 1 only

B. 2 only

C. 1 and 2 only

D. 1, 2 and 3 ✅

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Q4

Consider the following:

1. Crocodile has a four-chambered heart.

2. Frog has a three-chambered heart.

3. Birds are cold-blooded.

Answer:

A. 1 only

B. 2 only

C. 1 and 2 only ✅

D. All correct

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Q5

Identify the correct statements:

1. Starfish belongs to Echinodermata.

2. Oyster belongs to Mollusca.

3. Cockroach belongs to Arthropoda.

4. Whale is a fish.

Answer:

A. 1 and 2 only

B. 1, 2 and 3 only ✅

C. 2, 3 and 4 only

D. All correct

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Previous Exam-Oriented Facts

Arthropoda is the largest phylum by number of species.

Mollusca is the second-largest phylum.
Porifera exhibit a cellular level of organization.
Cnidaria possess cnidoblasts (nematocysts) for defense and prey capture.
Platyhelminthes are the first triploblastic animals.
Nematoda are the first pseudocoelomates.
Annelida are the first true coelomates with a closed circulatory system.
Echinodermata are exclusively marine and have a water vascular system.
Chordates are characterized by the presence of a notochord, dorsal hollow nerve cord, pharyngeal gill slits, and post-anal tail.
Crocodiles are the only living reptiles with a four-chambered heart.
Birds (Aves) and Mammals are warm-blooded (endothermic) vertebrates.