Topics to be learn :

  • Classification
  • Benefits of animal classification
  • Non Chordates and Chordate
  • Phylum Porifera
  • Phylum Coelenterata/Cnidaria
  • Phylum Platyhelminthes
  • Phylum Aschelminthes
  • Phylum Annelida
  • Phylum Arthropoda
  • Phylum Mollusca
  • Phylum Echinodermata
  • Phylum Hemichordata
  • Phylum Chordata and Class
Classification of Organisms
  • Presence or absence of nucleus
  • Unicellular or multicellular body
  • Presence or absence of cell wall
  • Mode of nutrition
Plant Classification
  • Organs: Presence or absence
  • Conducting tissues: Present for conduction of food and water or absent
  • Seeds: Presence or absence
  • Fruits: Whether seeds are enclosed or not
  • Cotyledons in seeds: One or two
Animal Classification
  • About 7 million animal species exist on Earth.
  • Classification helps in organizing these animals based on similarities and differences.
  • Systematic classification aids in studying this diversity.
History of Classification

Benefits of Animal Classification
  1. Convenient study: Animals grouped for easier learning.
  2. Understanding groups: Studying a few animals explains the whole group.
  3. Animal evolution: Insights into evolutionary processes.
  4. Accurate identification: Animals can be identified with precision.
  5. Relationships: Better understanding of animal relationships with other organisms.
  6. Habitat and role: Understanding of the animal's role in nature.
  7. Adaptations: Studying various adaptations in animals.

 Traditional Method of Animal Classification

Subphyla of Chordates
  • 1.Urochordata 2.Cephalochordata 3.Vertebrata (further divided into six classes)
Classes of Sub-phylum Vertebrata
  • 1. Cyclostomata, 2. Pisces, 3. Amphibia, 4. Reptilia, 5. Aves, 6. Mammalia

 Five Kingdom Classification by Robert Whittaker

  • All multicellular, heterotrophic organisms are placed in Kingdom Animalia.
Criteria for classification in this system include:
  • Body organization
  • Body symmetry
  • Body cavity
  • Germinal layers
  • Segmentation
New System of Animal Classification
(1) Grades of Organization
  • Animals can be classified based on their cellular organization.

(2) Body Symmetry
  • Classification based on the symmetry of the animal's body when cut along an imaginary axis.
 
(3) Germ Layers
  • Germ layers are formed during the early embryonic stage and give rise to tissues in animals.

 (4) Body Cavity (Coelom)
  • Coelom: Cavity between the body and internal organs.

(5) Segmentation
  • Segmentation: The body is divided into small, similar units called segments.
  • Example: Phylum Annelida exhibits segmentation.

Kingdom Animalia: Classification of Non-chordates into Ten Phyla

The non-chordates in Kingdom Animalia are classified into the following ten phyla:

  1. Protozoa
  2. Porifera
  3. Coelenterata/Cnidaria
  4. Platyhelminthes
  5. Aschelminthes
  6. Annelida
  7. Arthropoda
  8. Mollusca
  9. Echinodermata
  10. Hemichordata
(1) Phylum: Porifera
  • Body Structure: Simplest body plan; known as sponges. Body has many pores called ostia (for water intake) and oscula (for water outlet).
  • Habitat: Aquatic animals, mainly marine; some are freshwater.
  • Body Symmetry: Asymmetrical.
  • Characteristics: Have special collar cells. Supported by spicules (made of calcium carbonate or silica) or sponging fibers. Feed on small organisms brought in with water.
  • Germinal Layers and Coelom: Acoelomate, cellular grade.
  • Locomotion: Sedentary (attached to a surface, no movement).
  • Reproduction: Asexual (by budding). Sexual reproduction also possible. High ability for regeneration.
  • Examples:
    • Sycon, Euspongia (Bath sponge), Hyalonema, Euplectella.
(2) Phylum: Coelenterata/Cnidaria
  • Body Structure: Cylindrical body form is called polyp (e.g., Hydra). Umbrella-shaped body form is called medusa (e.g., Jellyfish).
  • Habitat: Mostly marine, a few in freshwater.
  • Body Symmetry: Radially symmetrical, diploblastic.
  • Characteristics: Tentacles around the mouth have cnidoblasts (stinging cells) for capturing prey and defense. Tentacles are used to inject toxins into prey.
  • Locomotion: Either sedentary (polyp) or free-swimming (medusa).
  • Germinal Layers and Coelom: Acoelomate, diploblastic.
  • Reproduction: Both asexual and sexual reproduction.
  • Examples: Hydra, Adamsia (Sea anemone), Physalia (Portuguese-man-of-war), Aurelia (Jellyfish), Corals.

(3) Phylum: Platyhelminthes (Flatworms)
  • Body Structure: Slender and flat like a leaf or strip; hence called flatworms.
  • Habitat: Mostly endoparasites (live inside host organisms). Some are free-living and aquatic.
  • Body Symmetry: Bilaterally symmetrical.
  • Characteristics: Flat body is a typical feature.
  • Locomotion: Swimming.
  • Germinal Layers and Coelom: Acoelomate (no body cavity). Triploblastic (body has three germ layers: endoderm, ectoderm, mesoderm).
  • Reproduction: Bisexual and hermaphroditic (both male and female reproductive organs in the same body). Sexual reproduction.
  • Examples: Planaria, Liverfluke, Tapeworm.
(4) Phylum: Aschelminthes (Roundworms)
  • Body Structure: Long, thread-like or cylindrical; known as roundworms.
  • Habitat: Either free-living or endoparasites.Free-living species may be aquatic or terrestrial.
  • Body Symmetry: Bilaterally symmetrical.
  • Germinal Layers and Coelom: Triploblastic. Pseudocoelomate (false body cavity).
  • Characteristics: Body is non-segmented and covered with a tough cuticle.
  • Locomotion: Swimming.
  • Reproduction: Unisexual.
  • Examples: Ascaris (intestinal worm), Filarial worm, Loa loa (eye worm).
(5) Phylum: Annelida
  • Body Structure: Long, cylindrical, and metamerically segmented body (segments are repeated).
  • Habitat: Mostly free-living, but some are ectoparasites. Free-living species are either marine, freshwater, or terrestrial.
  • Body Symmetry: Bilaterally symmetrical.
  • Germinal Layers and Coelom: Triploblastic. Eucoelomate (true body cavity).
  • Locomotion: Use setae, parapodia, or suckers for movement.
  • Characteristics: Body covered with a special cuticle.
  • Reproduction: Can be hermaphrodite or unisexual.
  • Examples: Earthworm, Leech, Nereis.
(6) Phylum: Arthropoda
  • Body Structure: Animals with jointed appendages. Largest phylum in the animal kingdom due to the high number of species.
  • Habitat: Found in all habitats, from deep oceans to high mountains.
  • Germinal Layers and Coelom: Triploblastic, eucoelomate.
  • Body Symmetry: Bilaterally symmetrical and segmented.
  • Locomotion: Methods include swimming and creeping.
  • Characteristics: Body covered with a chitinous exoskeleton.
  • Reproduction: Unisexual.
  • Examples: Crab, Spider, Scorpion, Millipede, Centipede, Cockroach, Butterfly, Honey bee.

(7) Phylum: Mollusca

  • Body Structure: Body is soft and slimy, hence termed as molluscs. Second largest phylum in the animal kingdom.
  • Habitat: Aquatic or terrestrial. Mostly marine, but some are freshwater dwellers.
  • Germinal Layers & Coelom: Triploblastic (three germ layers). Eucoelomate (true body cavity). Non-segmented and soft body.
  • Body Symmetry: Mostly bilateral symmetry (e.g., snails). Body has three divisions: head, foot, and visceral mass.
  • Locomotion: Methods include swimming or creeping on surfaces.
  • Characteristics: Visceral mass covered with a mantle. Mantle secretes a hard, calcareous shell - may be external, internal, or absent.
  • Reproduction: Generally unisexual.
  • Examples: Bivalve, Snail, Octopus, etc.
(8) Phylum: Echinodermata
  • Body Structure: Body has calcareous spines, giving the name echinoderms.
  • Habitat: Exclusively marine—found only in ocean.
  • Germinal Layers & Coelom: Triploblastic. Eucoelomate.
  • Body Symmetry: Radially symmetrical in adult stage. Bilateral symmetry in larval stage.
  • Locomotion: Uses tube-feet for locomotion and capturing prey. Some species are sedentary.
  • Characteristics: Have skeleton made of calcareous spines or ossicles (plates).
  • Reproduction: High regeneration ability. Usually unisexual.
  • Examples: Starfish, Sea urchin, Brittle star, Sea cucumber, etc.
(9) Phylum: Hemichordata
  • Body Structure: Body divided into three parts: proboscis, collar, and trunk. Notochord present only in the proboscis region—hence called hemichordates. Also known as ‘acorn worms’.
  • Habitat: Marine animals, living in burrows in sand.
  • Characteristics: Possess one to many pharyngeal gill slits.
  • Reproduction: Can be unisexual or hermaphrodite.
  • Examples: Balanoglossus, Saccoglossus.
(10) Phylum: Chordata
  • Chordates: Animals with a supporting notochord in their body.
Key Characteristics:
  • (1) Notochord present either throughout life or at least in the developmental stage.
  • (2) Pharyngeal gill slits present (at least during the developmental stage).
  • (3) Single, tubular, dorsal spinal cord.
  • (4) Ventrally situated heart.
Classification of Phylum Chordata 

A. Subphylum: Urochordata

  • Notochord only in the tail region of larvae.
  • Marine animals; adults are sedentary.
  • Larvae are free-swimming, later metamorphose into sedentary adults.
  • Body covered by test or tunic (skin-like covering).
  • Hermaphrodite animals.
  • Examples: Herdmania, Doliolum, Oikopleura.
B. Subphylum: Cephalochordata
  • Notochord extends through the entire body length.
  • Small, fish-like, marine animals.
  • Large pharynx with gill slits.
  • Unisexual animals.
  • Example: Amphioxus.
C. Subphylum: Vertebrata/Craniata
  • Divided into six classes based on further characteristic.
1. Class: Cyclostomata
  • Body Structure: Jawless mouth with a sucker. Soft skin without scales.
  • Thermoregulation: Cold-blooded animals.
  • Appendages: Paired appendages are absent.
  • Exoskeleton: Soft skin without scales. Endoskeleton is cartilaginous.
  • Habitat: Mostly ectoparasites, marine and aquatic.
  • Respiration: Occurs with gills.
  • Reproduction: Oviparous—egg-laying.
  • Examples: Petromyzon, Myxine, etc.
2. Class: Pisces
  • Habitat: Cold-blooded (poikilotherms) aquatic animals in marine and fresh waters.
  • Body Structure: Spindle-shaped body to minimize water resistance.
  • Thermoregulation: Cold-blooded animals.
  • Appendages: Paired & unpaired fins for swimming. Tail fin acts as a steering organ.
  • Exoskeleton: Exoskeleton in the form of scales. Endoskeleton is either cartilaginous or bony.
  • Respiration: Occurs with gills.
  • Reproduction: Oviparous—egg-laying.
  • Examples: Rohu, Pomfret, Sea horse, Shark, Electric ray, Sting ray, etc.
3. Class: Amphibia
  • Habitat: Aquatic during larval stage (aquatic respiration). Both aquatic and terrestrial during adult stage (aquatic & aerial respiration).
  • Appendages: Two pairs of appendages. Digits lack claws.
  • Exoskeleton: Exoskeleton is absent. Moist skin aids in respiration.
  • Body Structure: Neck absent. Prominent eyes with eyelids. No external ear, but tympanum present.
  • Thermoregulation: Cold-blooded animals.
  • Respiration: Gills during larval stage, skin in water and lungs on land in adulthood.
  • Reproduction: Eggs, larvae, adult metamorphosis.
  • Examples: Frog, Toad, Salamander, etc.
4. Class: Reptilia
  • Habitat: First true terrestrial animals in evolution with creeping movement. Some are aquatic.
  • Thermoregulation: Cold-blooded (poikilotherms).
  • Appendages: Two pairs of weak limbs. Digits with claws.
  • Exoskeleton: Dry, scaly skin.
  • Body Structure: Neck present between head & trunk. External ear absent.
  • Respiration: Lungs.
  • Reproduction: Eggs, young ones, adults.
  • Examples: Tortoise, Lizard, Snake, etc.
5. Class: Aves
  • Habitat: Adapted for aerial life. Warm-blooded (homeotherms).
  • Body Structure: Spindle-shaped to reduce air resistance during flight. Neck between head and trunk. Jaws modified into a beak.
  • Thermoregulation: Warm-blooded.
  • Appendages: Forelimbs modified into wings. Digits covered with scales and bear claws.
  • Exoskeleton: Feathers.
  • Respiration: Lungs aided by air sacs.
  • Reproduction: Oviparous, with parental care.
  • Examples: Peacock, Parrot, Pigeon, Duck, Penguin, etc.
6. Class: Mammalia
  • Habitat: Mostly terrestrial, with some aquatic and aerial species.
  • Key Feature: Mammary glands for nourishing young.
  • Thermoregulation: Warm-blooded.
  • Body Structure: Body divided into head, neck, trunk, and tail.
  • Appendages: Digits with nails, claws, or hooves.
  • Exoskeleton: Hair or fur.
  • Respiration: Lungs, aided by the diaphragm.
  • Reproduction: Mostly viviparous (live birth), with a few oviparous. Mammary glands secrete milk.
  • Examples: Elephant, Human, Kangaroo, Dolphin, Bat, etc.