Topics to be Learn :

  • Introduction
  • Criteria Used for Animal Classification
  • Animal Body Plan
  • Animal Classification
Basis for Classification:
  • Grades of organization
  • Body symmetry
  • Body cavity
  • Germ layers
  • Segmentation

Robert Whittaker's Contribution:

  • Proposed the five kingdom system of classification.

Need and Importance of Classification:

  • Facilitates accurate identification of animals.
  • Makes the study of animals convenient.
  • Helps in understanding animal relationships with other organisms.
  • Aids in understanding the habitat and role in nature of each animal.
  • Provides insight into the entire group by studying a few animals.
  • Helps in understanding adaptations.
  • Offers ideas about evolution of animals.

Criteria for Animal Classification:

Grades of Organization:

  • Cellular Level: Loose cell aggregates with some division of labor but no nervous coordination (e.g., Porifera).
  • Tissue Level: Cells performing the same function arranged as tissues (e.g., Coelenterates).
  • Organ Level: Tissues grouped to form organs, each specialized for a function (e.g., Platyhelminthes).
  • Organ System Level: Organs form functional systems with specific physiological functions (e.g., Aschelminthes, Annelids, Arthropods, Molluscs, Echinoderms, Chordates).
Body Cavity:
  • Acoelomates: Absent coelom (cavity)
  • Pseudocoelomates: False coelom
  • Eucoelomates: True coelem
Body Symmetry:
  • Asymmetry: Body cannot be divided into two identical halves in any plane.
  • Radial Symmetry: Body can be divided into two similar halves in multiple planes passing through the center.
  • Bilateral Symmetry: Body can be divided into two identical halves by a single median or vertical plane.
Animal Body Plans:

1. Cell Aggregate Body Plan:

  • Cells do not form tissues or organs.
  • Minimal differentiation and division of labor among cells.
  • Example: Phylum Porifera.

2. Blind Sac Body Plan:

  • Body is sac-like with a single opening.
  • Digestion and egestion occur through the same opening.
  • Example: Phylum Cnidaria.

3. Tube Within Tube Body Plan:

  • Digestive system is present in a tube-like body cavity.
  • Mouth and anus are present at separate ends.
  • Example: From Phylum Annelida onwards.
Germ Layers:
  • Diploblastic Animals: Have two germ layers: outer ectoderm and inner endoderm, separated by non-living mesoglea.
  • Triploblastic Animals: Have three germ layers: outer ectoderm, middle mesoderm, and inner endoderm.

Phylum Porifera (Sponges):

  • Habitat: Aquatic, mostly marine, some freshwater.
  • Forms: Sedentary animals (attached to substratum or rock).
  • Body Shape: Asymmetrical, colony of different types of cells with minimal division of labor.
  • Body Surface: Minute pores called ostia allow water to enter the spongocoel (body cavity), Water exits through a large opening called osculum, Flagella create water currents.
  • Circulation: Water circulates through the canal system, Cells absorb food, exchange gases, and release waste.
  • Digestive System: Lined with unique choanocytes or collar cells for digestion.
  • Endoskeleton: Made of calcareous/siliceous spicules or proteinaceous spongin fibers.
  • Reproduction: Asexual: Fragmentation and gemmule formation, Sexual: Gamete formation, internal fertilization, indirect development through larval stages.
  • Regeneration: High regenerative ability.
  • Examples: Scypha, Euspongia (Bath sponge), Euplectella (Venus’ flower basket).

Additional Characteristics:

  • Most primitive multicellular animals.
  • Intracellular digestion.
  • Hermaphrodites (both male and female reproductive organs).

Larval Stages of Porifera:

  • Parenchymula: Flagellate larvae of calcareous sponges.
  • Amphiblastula: Free swimming larval stage of Sycon and many other calcareous sponges.
Phylum Cnidaria:

Characteristics:

  • Habitat: Aquatic, mostly marine, some freshwater.
  • Forms: Sessile or free swimming.
  • Cnidoblasts: Stinging cells on tentacles for anchorage, offense, and defense.
  • Body Symmetry: Radially symmetrical.
  • Germ Layer: Diploblastic.
  • Body Cavity: Central cavity called coelenteron or gastrovascular cavity for digestion and circulation, with a single pore opening to the exterior (blind body-sac plan).
  • Body Form: Two forms: Polyp: Cylindrical, e.g., Hydra, Medusa: Umbrella-like, e.g., Aurelia (jellyfish).
  • Digestion: Both extracellular and intracellular.
  • Reproduction: Asexual: Budding and regeneration, Sexual: Gamete formation. Metagenesis: Alternation of polypoid generation with medusoid generation. Polyps produce medusae asexually, Medusae produce polyps sexually.
  • Examples: Hydra, Aurelia (Jellyfish), Physalia (Portuguese man-of-war), Adamsia (Sea anemone), Diploria (Brain coral), Gorgonia (sea fan).

Coral Reefs:

  • Ecosystem: Underwater, characterized by reef-building corals.
  • Biodiversity: Constitutes 25% of all marine species.
  • Types: Fringing, barrier, atoll.
  • Services: Tourism, fisheries, shoreline protection.
  • Threats: Cannot survive high temperatures, declining population due to climate change.

Sea Fan (Gorgonia):

  • Structure: Soft coral composed of numerous polyps growing together in a flat, fan-like pattern.
  • Skeleton: Does not produce calcium carbonate skeletons.

Phylum Ctenophora:

  • Common Names: Comb jellies, sea walnuts, acnidarians (lack cnidoblasts).
  • Habitat: Exclusively marine.
  • Forms: Free swimming.
  • Germ Layers: Diploblastic.
  • Body Symmetry: Radially symmetrical.
  • Body Plan: Blind-sac body plan.
  • Body Organization: Tissue level organization.
  • Locomotion: Achieved through eight rows of ciliated comb plates.
  • Bioluminescence: Characteristic feature; light produced by chemical reactions.
  • Digestion: Both extracellular and intracellular.
  • Reproduction: Sexual with indirect development.
  • Colloblasts: Sticky cells used for capturing prey.
  • Examples: Pleurobrachia, Crenoplana.

Bioluminescence:

  • Definition: Light produced by a chemical reaction in living organisms.
  • Organisms Exhibiting Bioluminescence:Marine organisms: Fishes, bacteria, ctenophores, jellyfish, Fireflies (Arthropoda).
  • Chemicals Involved: Luciferin and luciferase (or photoprotein).
  • Uses: Defense against predators, Finding mates, Hunting prey, Other vital activities.
Phylum Platyhelminthes (Flatworms):

Characteristics:

  • Body Shape: Dorsoventrally flattened.
  • Coelom: Acoelomates (no body cavity).
  • Germ Layers: Triploblastic (three germ layers).
  • Body Organization: Organ-system grade of organization.
  • Forms:Endoparasites: Most are parasitic with hooks and suckers for attachment; body covered by a cuticle. Free-Living: Few are free-living with ciliated bodies.
  • Digestive System: Parasitic Forms: Generally lack a digestive system. Free-Living Forms: Incomplete digestive system.
  • Body Plan: Blind-sac body plan.
  • Excretion and Osmoregulation: Occurs via flame cells or protonephridia.
  • Reproduction: Mostly hermaphrodites (bisexual), Self-fertilization is common,Some exhibit high regenerative capacity and polyembryony (development of multiple embryos from a single fertilized egg).
  • Examples: Planaria, Taenia (Tapeworm), Fasciola (Liver fluke).

Additional Notes:

  • Parasitic Forms: Absorb nutrients directly through the body surface.
  • Planaria: Notable for high regenerative capacity.

Liver Fluke (Parasitic Adaptations):

  • Hooks and Suckers: For attachment to host.
  • Cuticle: Covers body.
  • Digestive System: Lacks digestive system.
  • Reproduction: Hermaphroditic.
Phylum Aschelminthes (Nemathelminthes):

Characteristics:

  • Forms: Mostly parasitic; few free-living (e.g., Planaria).
  • Body Shape: Long, cylindrical, thread-like, circular in cross-section; known as roundworms.
  • Body Symmetry: Bilaterally symmetrical.
  • Coelom: Pseudocoelomate (body cavity is not fully lined by mesoderm).
  • Germ Layers: Triploblastic (three germ layers).
  • Body Plan: Tube within a tube type body plan.
  • Body Covering: Tough, resistant cuticle.
  • Muscles: Longitudinal muscles present; circular muscles absent.
  • Digestive System: Complete alimentary canal with mouth and anus at opposite ends.
  • Excretion: Via canals or gland cells.
  • Nervous System: Consists of a nerve ring and nerves.
  • Reproduction: Unisexual: Separate sexes,Fertilization: Internal,Development: May or may not include larval stages, Sexual Dimorphism: Males and females differ in appearance.
  • Examples: Ascaris (Roundworm), Wuchereria (Filarial worm), Ancylostoma (Hookworm).
  • Habitat: Aquatic and terrestrial.

Ascaris (Roundworm):

  • Body: Long, cylindrical, thread-like.
  • Body Covering: Tough, thick, resistant cuticle.
  • Sexual Dimorphism: Male: Shorter, narrower, curved posterior end, with pair of penial setae for copulation, Female: Longer, broader, straight posterior end, without penial setae.
Phylum Annelida (Segmented Worms)

Characteristics of Phylum Annelida:

  • Forms: Aquatic (living in water), Ectoparasitic (living on the surface of other organisms),Free-living (independent organisms),Burrowing in moist soil
  • Body Symmetry: Bilaterally symmetrical (two equal halves)
  • Body Coelom: True coelomates (body cavity fully lined by mesoderm)
  • Segmentation: Metamerically segmented (body divided into repeating segments), Clitellum: A special region for reproduction
  • Digestive System: Complete alimentary canal (mouth to anus)
  • Locomotion: Setae (bristles in earthworms), Parapodia (lateral extensions in Nereis), Suckers (in leeches), Muscles: Longitudinal and circular muscles help in movement
  • Nervous System: Nerve ring (ring of nerves around the pharynx),Ventral solid and ganglionated nerve cord (central nerve cord with ganglia)
  • Reproduction: Mostly hermaphrodites (both male and female organs),Dioecious (separate sexes, e.g., Nereis)
  • Respiration: Gas exchange through the body wall
  • Circulation: Closed circulatory system (blood enclosed within vessels)
  • Excretion and Osmoregulation: Nephridia (excretory organs)
  • Examples: Nereis (aquatic annelid), Pheretima (earthworm), Hirudinaria (leech),

General Traits in Phylum Annelida:

  • Tube within tube body plan
  • Triploblastic (three germ layers)
  • Coelomate (having a body cavity)
  • Organ-system level of organization

Hermaphroditism in Annelida:

Merits:

  • Assured fertilization
  • Conservation of energy (less effort in finding a mate)
  • Maximized mating frequency

Demerits:

  • Higher energy requirement (to maintain both reproductive systems)
  • Limited gene diversity
Phylum Arthropoda (Joint-legged Animals)

Characteristics of Phylum Arthropoda:

  • Habitat: Omnipresent (found everywhere)
  • Forms: Solitary or colonial (living alone or in groups), Free-living, with some exceptions like Barnacles (sedentary) and parasitic forms (e.g., female mosquito, bed bug)
  • Body Symmetry: Bilaterally symmetrical (two equal halves)
  • Germ Layers: Triploblastic (three germ layers)
  • Body Cavity: Eucoelomates (true body cavity)
  • Body Plan: Tube within tube body plan
  • Level of Organization: Organ system level
  • Special Features: Jointed appendages (legs and other body parts with joints), Polymorphism in some insects (e.g., honey bees, ants, termites)
  • Exoskeleton: Chitinous exoskeleton (tough outer covering), Moulting/Ecdysis: Shedding of exoskeleton to allow growth
  • Body Division: Divided into head, thorax, and abdomen
  • Segmentation: Metameric segmentation (repeated segments)
  • Digestive System: Complete, divided into foregut, midgut, and hindgut
  • Circulation: Open circulatory system with haemocoel (body cavity for blood flow)
  • Respiration: Through gills, trachea, book lungs, or book gills
  • Excretion: Through green glands, Malpighian tubules, or coxal glands
  • Nervous System: Nerve ring and double ventral ganglionated nerve cord
  • Sense Organs: Antennae, simple or compound eyes, and various receptors
  • Reproduction: Sexes are generally separate with distinct sexual dimorphism, Mostly oviparous (egg-laying), except Scorpions, Internal fertilization, Direct or indirect development with metamorphosis, Parthenogenesis in some (e.g., honey bees, bugs)

Useful & Harmful Arthropods:

Beneficial Arthropods:

  • Honey bees (Apis): For honey and wax
  • Silk worms: For silk production
  • Edible arthropods: Lobsters, prawns, crabs

Harmful Arthropods:

  • Vectors of diseases: Mosquitoes
  • Pests: Locusts (Locusta)
  • Living fossils: King crab (Limulus)
  • Other Examples: Cockroach (Periplaneta), butterfly, scorpion (Hottentotta), millipede

Phylum Arthropoda - Success Factors:

  • Largest phylum of kingdom Animalia, including diverse forms like lobsters, prawns, crabs, insects, millipedes, locusts, and honey bees.
  • Omnipresent with great variety of adaptations in terrestrial and aquatic habitats.
  • Chitinous exoskeleton enables survival in almost all environments and provides defense against predators.
  • Jointed appendages allow complex movements.
  • Moulting or ecdysis allows growth.
  • Metamerically segmented body aids in movement across diverse environments.
Phylum Mollusca (Soft-Bodied Animals)

Characteristics of Phylum Mollusca:

  • Habitat: Aquatic (found in water) or in marshy places; some are terrestrial (land-dwelling)
  • Forms: Free-living or sedentary (stationary)
  • Body Plan: Soft-bodied, Tube within tube body plan
  • Body Symmetry: Mostly bilaterally symmetrical, Some are asymmetrical due to torsion (twisting of the body)
  • Body Division: Three main parts: Head, Foot (muscular, located ventrally), Visceral mass (contains organs), Mantle: Thick, muscular fold of body wall enclosing the visceral mass, Shell: Hard, calcareous; may be external, internal, or absent
  • Digestive System: Well-developed and complete, Radula: Rasping organ with rows of teeth in the buccal cavity (helps in feeding)
  • Respiration: Aquatic forms: Ctenidia (feather-like gills), Terrestrial forms: Lungs
  • Circulatory System: Open type (except in Sepia, which has a closed system), Blood contains haemocyanin (copper-containing blue pigment)
  • Excretion: By kidney-like structures called Organ of Bojanus
  • Nervous System and Sense Organs: Three pairs of ganglia interconnected by commissures and connectives.
  • Sense Organs: Eyes: Vision, Tentacles: Tactile sensation, Osphradia: Tests purity of water
  • Reproduction: Sexes are usually separate, Oviparous (egg-laying), Development: Direct or indirect
  • Examples: Pila, Spisula (Bivalve), Octopus (Devil fish), Sepia (Cuttlefish), Chaetopleura (Chiton), Pinctada (Pearl oyster), Loligo (Squid), Aplysia (Sea hare), Dentalium (Tusk shell).
Economic Importance of Molluscs:
  • Pearl oyster (Pinctada): Produces precious pearls.
  • Edible Molluscs: Many are consumed as food.
  • Molluscan Shells: Rich source of calcium.
Phylum Echinodermata:
  • Habitat: Exclusively marine organisms.
  • Forms: Can be solitary, sedentary, free-living, or gregarious. Typically benthic (live on the ocean floor).
  • Body Symmetry: Adult echinoderms: Radially symmetrical (pentamerous symmetry). Larval forms: Bilaterally symmetrical.
  • Body Shape: Shapes can be spherical, elongated, or star-shaped.
  • Body Structure: Endoskeleton made of calcareous ossicles. Presence of spines on the body (reason for the name echinoderms). Body has two surfaces: Oral surface (where the mouth is located, ventrally). Aboral surface (where the anus is located, dorsally). Body lacks clear divisions.
  • Water Vascular System: Unique system for locomotion, food capture, and respiration. Madreporite: Opening through which water enters the system.
  • Digestive System: Complete digestive tract.
  • Respiration: Done via peristomial gills, papillae, and respiratory tree (in different species).
  • Circulatory & Excretory Systems: Both systems are absent.
  • Nervous System: Simple structure with: Nerve ring around the mouth. Radial nerves in the arms.
  • Reproduction & Development: Sexes are usually separate (though some species are bisexual). Fertilization is external. Development occurs through larval stages (indirect development). Echinoderms have a high capacity for regeneration. Larvae are free-swimming.
  • Examples: Asterias (Sea star), Cucumaria (Sea cucumber), Echinus (Sea urchin), Antedon (Sea lily),Ophiothrix (Brittle star).

Phylum Hemichordata (Half Chordates)

Characteristics of Phylum Hemichordata:

  • Habitat: Exclusively marine animals, typically found at the bottom of the sea in burrows, Mostly free-living; some like Rhabdopleura are sedentary
  • Body Shape and Division: Soft and vermiform (worm-like), Unsegmented body, Divided into three parts: Proboscis, Collar, Trunk.
  • Digestive System: Complete alimentary canal, Shape: Straight or ‘U’-shaped, Buccal cavity contains a rod-like buccal diverticulum
  • Respiration: Numerous gills in two longitudinal rows located in the pharyngeal region, Gills open via gill slits
  • Circulatory System: Simple and open type
  • Excretion: Carried out by the glomerulus
  • Nervous System: Nervous tissue embedded in the epidermis on both the dorsal and ventral sides
  • Reproduction and Development: Sexes are separate (sometimes bisexual), Fertilization is external, Development occurs indirectly through a free-swimming larva
  • Examples: Balanoglossus, Saccoglossus
Difference Between Chordates and Non-Chordates

Phylum Chordata

Characteristics of Chordates:

  • Notochord: Present as a cartilaginous rod at least during early embryonic life.
  • Gill Slits: Found in the pharyngeal (neck) region.
  • Nerve Cord: Hollow, dorsal nerve cord running throughout the length of the body.
  • Heart: Positioned ventrally.

Subphyla of Phylum Chordata:

  • Urochordata
  • Cephalochordata
  • Vertebrata

Protochordates: Urochordata and Cephalochordata are collectively known as Protochordates.

Subphylum Urochordata (Tunicates or Ascidians)

Features of Urochordata:

  • Habitat: Exclusively marine.
  • Body Covering: Soft body covered by a ‘test’ or ‘tunic’ made of tunicine.
  • Notochord: Present only in the tail of the larva and lost during metamorphosis.
  • Respiration: Pharynx with many gill slits aids in respiration.
  • Circulation: Closed circulatory system.
  • Reproduction: Development is indirect.
  • Examples: Herdmania, Salpa, Doliolum, Ascidias.
Subphylum Cephalochordata (Lancelets)

Features of Cephalochordata:

  • Habitat: Exclusively marine, often partly buried in soft marine sediments.
  • Notochord: Extends throughout the entire length of the body and persists throughout life.
  • Muscle Blocks: Myotomes are present.
  • Tail: Post-anal tail is present.
  • Circulatory System: Closed type, but blood lacks pigment.
  • Example: Branchiostoma.
Subphylum Vertebrata

Characteristics: Notochord: Replaced by a cartilaginous or bony vertebral column in these chordates.

Division: Vertebrata is divided into two main divisions:
  • Agnathostomata: No jaws.
  • Gnathostomata: Jaws present.
Division Agnathostomata (Jawless Vertebrates)

Class Cyclostomata (Cyclostomes):

  • Body Structure: Jawless, eel-like animals.
  • Skin: Soft, smooth skin with unicellular mucus glands; no scales.
  • Fins: Median fins are present; paired fins are absent.
  • Feeding: Ectoparasitic with a sucking and circular mouth without jaws.
  • Skeleton: Cranium and vertebral column made of cartilage.
  • Digestive System: Lacks a stomach.
  • Respiration: 6 to 15 pairs of gill slits without operculum.
  • Circulation: Heart is two-chambered (one auricle and one ventricle).
  • Reproduction: Single, large gonad without gonoduct. External fertilization. Anadromous: Migrate from marine to freshwater to spawn; die after spawning. Larvae undergo metamorphosis and return to the ocean.
  • Examples: Petromyzon (Lamprey), Myxine (Hagfish).
Division Gnathostomata (Jawed Vertebrates)

Superclasses: Pisces: Bears fins & Tetrapoda: Bears four limbs.

Superclass Pisces (Fishes)

Important Features:

  • Habitat: Aquatic, found in freshwater, marine, and brackish environments.
  • Body Temperature: Poikilothermic (cold-blooded) – body temperature varies with the environment.
  • Sensory Organs: Lateral line system with rheoreceptors to detect water currents.
  • Locomotion: Body muscles and fins facilitate movement; caudal fin acts as a steering wheel.
  • Skeleton: Exoskeleton made of dermal scales; skeleton can be bony or cartilaginous.
  • Body Shape: Streamlined, boat-shaped body for efficient swimming.
  • Respiration: Through gills.
  • Circulation: Single, closed circulatory system with a two-chambered heart (ventral position). The heart contains only deoxygenated blood, known as a venous heart.
  • Nervous System: Well-developed brain with prominent olfactory lobes.
  • Reproduction: Separate sexes, Most are oviparous (egg-laying); some are viviparous (live-bearing).
Class Chondrichthyes (Cartilaginous Fish)

Key Features:

  • Endoskeleton: Made entirely of cartilage.
  • Exoskeleton: Composed of placoid scales (minute, tooth-like scales).
  • Mouth Position: Ventral (located on the underside of the body).
  • Fins: Single dorsal fin, Two pairs of lateral fins: pectoral and pelvic fins.
  • Gill Slits: 5 to 7 pairs of gill slits present without an operculum (gill cover).
  • Caudal Fin: Heterocercal (asymmetrical tail fin, with one lobe larger than the other).
  • Reproductive Structures: Males have claspers (copulatory organs) located between the pelvic fins.
  • Buoyancy: Air bladder absent, so they must swim constantly to maintain buoyancy.
  • Reproduction: Many are viviparous (give birth to live young).
  • Examples: Scolidon (Dogfish), Pristis (Sawfish), Electric ray, Common skate, Hammerhead shark, Carcharodon (Great white shark), Trygon (Stingray),Anoxypristis
Class Osteichthyes (Bony Fish)

Key Features:

  • Endoskeleton: Made of bones.
  • Exoskeleton: Composed of large, flat, and overlapping cycloid or ctenoid scales.
  • Mouth Position: Typically terminal (located at the front of the body).
  • Fins: Two dorsal fins present.
  • Gill Structure: Four pairs of gills covered by an operculum (gill cover).
  • Reproductive Structures: Males lack claspers.
  • Buoyancy: Air bladder present to maintain buoyancy, allowing the fish to stay afloat without constant swimming.
  • Reproduction: Most are oviparous (egg-laying).
  • Examples: Exocoetus (Flying fish), Hippocampus (Sea horse), Labeo rohita (Rohu), Pomphret, Catla (Katla), Clarius (Magur), Pterophyllum (Angelfish), Bombay duck, Lungfishes
Superclass Tetrapods

Overview:

  • Tetrapods are a diverse group of vertebrates that include amphibians, reptiles, birds, and mammals.
  • They are characterized by the presence of two pairs of appendages (with exceptions like limbless snakes).
Class Amphibia (Amphibians) - Detailed Features

Habitat and Lifestyle:

  • Dual Habitat: Amphibians live both on land and in freshwater.
  • Body Temperature: They are poikilothermic (cold-blooded), meaning their body temperature varies with the environment.

Body Structure:

  • Body Division: Differentiated into head and trunk.
  • Limbs: Two pairs of limbs arise from pectoral and pelvic girdles, aiding in locomotion. Some adults may lack a neck and tail (with exceptions).
  • Skin: Moist and glandular, containing mucous glands. Exoskeleton is absent.

Sensory and Excretory Systems:

  • Eyes: Eyelids are present.
  • Ear: Tympanum acts as the ear.
  • Cloaca: A common chamber for the excretion of waste products, digestive products, and gametes.

Circulatory and Respiratory Systems:

Circulation:
  • Closed circulatory system.
  • Three-chambered heart (with two atria and one ventricle) located ventrally.
  • RBCs (Red Blood Cells) are biconvex and nucleated.
Respiration: Through skin, lungs, and buccopharynx.

Reproduction and Development: Separate sexes. Oviparous (egg-laying). External fertilization. Development is indirect, involving an aquatic larval stage. They undergo metamorphosis (a transformation from larva to adult form).

Examples: Rana (Frog), Bufo (Toad), Salamandra (Salamander), Ichthyophis (Limbless amphibian), Hyla (Tree frog).

Class Reptilia - Advanced Notes

Overview:

  • Reptilia includes reptiles, the first true terrestrial vertebrates.
  • Reptiles are characterized by adaptations for a fully terrestrial life, including specialized locomotion and body coverings.
Salient Features of Reptilia:

Habitat:

  • Terrestrial: Primarily land-dwelling.
  • Some are aquatic or semi-aquatic, found in marshy areas.

Locomotion:

  • Limbs: Most reptiles use limbs for movement, which are typically pentadactyl (five digits) with clawed toes.
  • Snakes: Limbless and move by slithering on their belly.

Body Temperature: Poikilothermic: Body temperature fluctuates with the environment.

Exoskeleton: Skin: Dry, non-glandular, Covering: Composed of epidermal scales, scutes, shields, or plates. Skin Shedding: Lizards and snakes periodically shed their skin.

Sensory and Excretory Systems: Ear: Tympanum (eardrum) is present for hearing.

Circulatory System:

  • Heart: Two complete auricles, Ventricles are incompletely partitioned (except in crocodiles, which have a fully four-chambered heart).

Nervous System:

  • Brain: Well-developed, with improved olfactory lobes and cerebellum compared to amphibians.

Reproduction:

  • Sexes: Separate with pronounced sexual dimorphism.
  • Fertilization: Internal.
  • Reproduction: Primarily oviparous (egg-laying), Some species, like the viper, are viviparous (live-bearing), Minimal parental care.

Examples: Naja naja (Cobra), Hemidactylus (Wall lizard), Chelonia (Turtle), Crocodilus (Crocodile), Testudo (Tortoise), Chameleon (Tree lizard), Bangarus (Krait), Vipera (Viper).

Class Aves (Birds)

General Features:

  • Habitat: Primarily aerial. Some are terrestrial or aquatic.
  • Locomotion: Forelimbs: Modified into wings for flying. Hind Limbs: Used for walking, grasping, or swimming (webbed toes for aquatic birds).
  • Body Division: Head, neck, trunk, and tail.
  • Body Shape: Streamlined to reduce flight resistance.
  • Body Temperature: Warm-blooded (homeotherms); maintains constant temperature.
  • Exoskeleton: Feathers. Scales on hind-limbs. Thin, dry, non-glandular skin except for the uropygial gland (oil gland).
  • Endoskeleton: Hollow (pneumatic) bones to reduce weight.
  • Digestive System: Beaks (no teeth). Presence of crop and gizzard.
  • Circulatory System: Heart: Four-chambered (two auricles, two ventricles). Blood: Red, with biconvex and nucleated RBCs. Double circulation.
  • Respiration: Lungs with air sacs for buoyancy.
  • Nervous System: Enlarged brain with a well-developed cerebellum for balance.
  • Reproduction: Separate sexes with sexual dimorphism. Female has only left ovary and left oviduct for reduced weight. Internal fertilization, oviparous, with well-developed parental care.
  • Examples: Columba (Pigeon), Psittacula (Parrot), Struthio (Ostrich), Aptenodytes (Penguin), Corvus (Crow), Neophron (Vulture), Passer (Sparrow)

Adaptations for Flying:

  • Wings as forelimbs.
  • Streamlined body shape.
  • Pneumatic bones.
  • Only left ovary and oviduct in females.
  • Feathers for flight.
Class Mammalia (Mammals)

General Features:

  • Special Feature: Mammary glands for milk production.
  • Habitat: Terrestrial, aquatic, aerial, and arboreal.
  • Locomotion: Limbs adapted for various functions like walking, climbing, swimming.
  • Body Division: Head, neck, trunk, and tail. External ear (pinna).
  • Body Temperature: Warm-blooded (homeotherms); maintains constant temperature.
  • Exoskeleton: Hair, fur, nails, hooves, horns.
  • Skin: Glandular with sweat and sebaceous (oil) glands.
  • Mouth Cavity: Heterodont dentition (incisors, canines, premolars, molars).
  • Circulatory System: Heart: Four-chambered (two auricles, two ventricles). RBCs: Biconcave and enucleated (except in camels). Red blood.
  • Respiration: Lungs.
  • Nervous System: Highly developed brain with a corpus callosum.
  • Reproduction and Development: Few oviparous (e.g., platypus). Marsupials (e.g., kangaroo) with pouches. Placental and viviparous in most.
  • Examples: Bat, Rattus (Rat), Macaca (Monkey), Camelus (Camel), Whale, Homo (Human),Canis (Dog), Felis (Cat), Elephas (Elephant), Equus (Horse), Pteropus (Flying Fox)
  • Oviparous: Ornithorhynchus (Platypus)
  • Viviparous: Macropus (Kangaroo)