Zoology Lecture Notes PDF

Phylum Nematoda: Overview  Common Names: Roundworms, threadworms, nematodes  Etymology: Derived from Greek words nema (thread) and odes (resembling)  Habitat: Ubiquitous - terrestrial, aquatic; free-living or parasitic  Body Size: Microscopic (82μm) to macroscopic (>8m)...

Phylum Nematoda: Overview  Common Names: Roundworms, threadworms, nematodes  Etymology: Derived from Greek words nema (thread) and odes (resembling)  Habitat: Ubiquitous - terrestrial, aquatic; free-living or parasitic  Body Size: Microscopic (82μm) to macroscopic (>8m)  Body Structure: Cylindrical, unsegmented; pseudocoelomate (with a body cavity), covered by a protective cuticle Characteristics 1. Tissue Type: Eumetazoan (true tissues) 2. Germ Layers: Triploblastic (ectoderm, mesoderm, endoderm) 3. Symmetry: Bilateral symmetry 4. Digestive System: Complete (mouth and anus) 5. Excretory System: Poorly developed; includes excretory pore 6. Circulatory System: Absent; relies on diffusion 7. Nervous System: Nerve cords, ganglia, paired sense organs (amphids - anterior; phasmids - posterior) 8. Reproduction: Sexual (gonochoristic - separate sexes), internal fertilization; males often have hooked posterior ends Adaptations  Cuticle: Noncellular protective covering  Stylet: Piercing mouthpart for feeding and secretion  Valve: Regulates food movement, prevents regurgitation  Movement: Whip-like motion due to longitudinal muscles Classes and Examples 1. Class Chromadorea o Features: Amphids (pore-like/slit-like), phasmids present or absent, esophagus with 3–5 glands o Examples:  Ascaris lumbricoides (intestinal roundworm; human parasite)  Wuchereria bancrofti (causes filariasis/elephantiasis)  Caenorhabditis elegans (model organism for genetics, aging, and neuroscience) 2. Class Enoplea o Features: Amphids (pocket-like for smell), phasmids present, bottle- shaped esophagus o Examples:  Trichinella spiralis (pork worm; causes trichinosis)   Trichuris trichiura (whipworm; causes trichuriasis) Functions and Importance  Environmental Roles: Decomposers, bacterial and fungal feeders  Pathogenic Roles: Cause diseases in humans, animals, and plants (e.g., crop damage)  Research Use: o C. elegans: First multicellular organism with a fully sequenced genome; widely used in biological research  Economic Impact: Major agents of crop losses Key Features for Parasitic Nematodes  Life Cycle: Complex, involving intermediate and definitive hosts  Examples of Diseases: o Filariasis (by Wuchereria bancrofti) o Ascariasis (by Ascaris lumbricoides) o Trichinosis (by Trichinella spiralis) Study Guide: Phylum Platyhelminthes Overview  Common Name: Flatworms  Etymology: Derived from Greek platy (flat) and helminth (worm)  Habitat: Aquatic (marine and freshwater), terrestrial in moist environments  Symmetry: Bilateral symmetry  Body Plan: Triploblastic, acoelomate (no body cavity)  Size: Microscopic to over 20m (e.g., tapeworms) Key Features 1. Tissue Organization: Eumetazoan (true tissues) 2. Nervous System: Paired nerve cords, ganglia concentrated in the head (cephalization) 3. Digestive System: Incomplete, single opening (mouth and anus) 4. Excretory System: Flame cells in protonephridia for fluid waste removal 5. Reproductive System: Mostly monoecious (hermaphroditic), sexual (cross- fertilization) and asexual (fission, regeneration) 6. Circulatory & Respiratory Systems: Absent; rely on diffusion Classification and Examples 1. Class Turbellaria (Free-living planarians) o Habitat: Marine, freshwater, and moist terrestrial o Example: Planaria o Feeding: Preys on small organisms, external digestion via secreted enzymes o Reproduction: Cross-fertilization, fission, and regeneration 2. Class Monogenea (Parasitic flatworms) o Hosts: Ectoparasites on fish skin, gills, or cloaca o Attachment Structures: Hooks, suckers, clamps o Example: Gyrodactylus elegans o Lifecycle: Direct lifecycle (one host) 3. Class Trematoda (Endoparasitic flukes) o Diseases: Schistosomiasis (snail fever) o Hosts: Intermediate (snails) and definitive (humans, mammals) o Examples:  Schistosoma mansoni, S. japonicum o Prevention: Avoid freshwater in endemic areas, molluscicides, good hygiene 4. Class Cestoda (Tapeworms) o Structure: Scolex (head) with hooks/suckers, segmented body (proglottids) o Nutrient Absorption: No digestive system; absorb nutrients from host o Examples:  Taenia solium (pork tapeworm), T. saginata (beef tapeworm) o Lifecycle: Involves intermediate (e.g., pigs, cattle) and definitive hosts (humans) Diseases and Lifecycle Highlights  Schistosomiasis: o Caused by Schistosoma species o Symptoms: Abdominal pain, diarrhea, blood in urine or stool o Prevention: Avoid contaminated water, use molluscicides o Treatment: Praziquantel  Taeniasis: o Caused by tapeworms (Taenia species) o Transmission: Consumption of undercooked meat o Symptoms: Abdominal pain, nutrient deficiency Key Concepts to Study 1. Defining Characteristics: Tissue layers, body symmetry, and organ systems  2. Parasitic Adaptations: Lifecycle strategies, host interactions, and nutrient acquisition 3. Lifecycle: o Examples: Schistosome lifecycle (snail to human), tapeworm lifecycle (intermediate to definitive host) 4. Prevention and Control: Hygiene, education, and environmental management Quick Notes  Respiration and Circulation: Absent; diffusion suffices for oxygen and waste exchange.  Reproductive Adaptability: High regeneration capability aids survival and proliferation.  Environmental Role: Indicators of ecosystem health (Turbellaria) and parasitic disease spread. Study Notes: Phylum Annelida Key Features  Name Origin: Latin annellus (small ring), commonly called "annelids."  Body Structure: o Elongate, segmented body (metameres or somites). o Thin, flexible body wall. o Bilateral symmetry, triploblastic (3 germ layers), true coelom (eucoelomate). o Segments: Marked by circular rings (annuli), each with nervous, circulatory, and excretory systems. o Lateral Structures:  Parapodia (in some): Lateral extensions for gas exchange or movement.  Setae (chaetae): Bristle-like structures for locomotion.  Circulatory and Respiratory Systems: o Closed circulatory system with hemoglobin or chlorocruorin (oxygen- carrying pigments). o Respiration via gills or body wall (e.g., earthworms). Functions and Systems 1. Digestive System: o Complete digestive tract (mouth to anus). o Some species are deposit feeders (extract organic material from sediments). 2. Reproductive System: o Hermaphroditic or dioecious. o Sexual reproduction (e.g., copulation).  o Earthworms have a clitellum for mucus secretion during reproduction. 3. Nervous System: o Simple brain (cerebral ganglia) and double ventral nerve cords. o Sense organs: photoreceptors (eyes), nuchal organs, statocysts (touch detection). 4. Excretory System: o Nephridia ("little kidneys") collect and expel wastes through body wall. Classification 1. Class Polychaeta (e.g., Nereis sp., Sabella): o Largest group (~65%, >10,000 species). o Parapodia with setae for movement and gas exchange. o Free-living or tube-dwelling. o Mostly marine, gonochoristic (separate sexes). 2. Class Clitellata: o Subclass Oligochaeta (e.g., Earthworms):  Few setae; terrestrial or freshwater.  Contribute to soil fertility and aeration.  Gas exchange through body wall. o Subclass Hirudinea (e.g., Leeches):  Posterior sucker, razor-like jaws in some.  Use anticoagulants (hirudin) and anesthetics.  Medicinal use: anti-clotting, post-surgery care. Examples and Importance  Ecological Roles: o Soil aeration and decomposition (earthworms). o Organic matter recycling in marine/freshwater habitats.  Economic and Medicinal Importance: o Vermiculture (earthworms for fertilizers). o Medicinal leeches for anticoagulation and tissue healing.  Indicator Species: Sludge worms thrive in polluted waters, indicating pollution levels. Locations and Habitats  Found in diverse environments: o Marine: Polychaetes dominate. o Freshwater & Terrestrial: Earthworms, leeches. Diseases and Risks  Few parasitic risks; most annelids are beneficial. Study Notes for Phylum Mollusca General Overview  Definition: Soft-bodied organisms; often possess shells.  Diversity: Second most abundant animal group (~100,000 living species, 70,000 fossils).  Distribution: Cosmopolitan (marine, freshwater, terrestrial).  Examples: Snails, slugs, squids, octopuses, clams. Defining Characteristics 1. Body Structure: o Triploblastic, bilaterally symmetrical, coelomates. o No segmentation; body parts: head, visceral mass, muscular foot. o Mantle: Dorsal epithelium secretes shell (external, internal, or absent). o Shell composed of three layers: periostracum, prismatic, nacreous. 2. Radula: o Cuticular band of teeth in esophagus (absent in bivalves). 3. Circulation and Respiration: o Open or closed circulatory systems. o Gas exchange via ctenidia (gills), lungs, or mantle. 4. Nervous and Sensory Systems: o Centralized ganglia, osphradium for monitoring water, and chromatophores in cephalopods. 5. Excretion: o Metanephridia: Specialized kidneys. Classification by Foot & Shell Characteristics 1. Class Aplacophora: o No shell; worm-like with calcareous spines. o Examples: Solenogastres, Caudofoveata. 2. Class Monoplacophora: o Cap-shaped shell; deep-water species. o Example: Neopilina. 3. Class Polyplacophora (Chitons): o Eight dorsal plates; marine, rocky intertidal zones. o Example: Tonicella lineata. 4. Class Gastropoda:  o Univalve (spiraled shell); largest class. o Torsion causes visceral asymmetry. o Examples: Snails (Achatina), slugs, limpets. 5. Class Cephalopoda: o Advanced; head with tentacles, jet propulsion. o Shell absent or reduced (e.g., octopus, squid). o Examples: Octopus, Nautilus. 6. Class Bivalvia: o Two shells; filter feeders. o No head, no radula. o Examples: Clams (Tridacna gigas), oysters. 7. Class Scaphopoda: o Tubular shell open at both ends. o No head; mantle acts as gills. o Example: Dentalium (tusk shell). Economic and Biological Importance  Food: Key food source for humans and animals.  Industry: Pearls, shell crafts, biomedical research.  Environmental: Indicators of ecosystem health. Diseases and Hosts  Intermediate hosts for parasites (e.g., trematodes in gastropods). Key Larval Stages 1. Trochophore: Basic larva stage. 2. Veliger: Develops foot and shell. PHYLUM ARTHROPODA Key Description:  From Greek: arthon = joint, pous = foot; “joint-footed” animals.  Most abundant and diverse animals, ~1 million species (~80% of all animals). GENERAL CHARACTERISTICS 1. Body Structure: o Segmented body with 3 tagmata (head, thorax, abdomen).  o Covered by a chitinous exoskeleton (protection, flexibility, mobility). o Jointed appendages. o Bilateral symmetry. 2. Circulatory & Respiratory System: o Open circulatory system. o Terrestrial forms use tracheal tubes; aquatic forms use gills. 3. Nervous System & Senses: o Ventral nerve cord. o Compound eyes with ommatidia for detecting brightness and color. 4. Adaptations: o Versatile exoskeleton (protection, mobility). o Efficient segmentation and appendages for locomotion. o Highly developed sensory organs. o Metamorphosis reduces competition between larvae and adults. CLASSIFICATION 1. Subphylum Trilobita (Trilobites)  Fossil marine arthropods, all extinct (~200 million years ago). 2. Subphylum Chelicerata  Defining feature: Chelicerae (pincers/fangs).  Classes: o Merostomata: Horseshoe crabs. o Arachnida: Spiders, scorpions, ticks, mites. 3. Subphylum Crustacea  Defining feature: Two pairs of antennae.  Classes: o Branchiopoda: Brine shrimps, water fleas. o Malacostraca: Crabs, lobsters, prawns. o Cirripedia: Barnacles. 4. Subphylum Myriapoda  Many legs; distinct head and trunk.  Classes: o Diplopoda: Millipedes (herbivores). o Chilopoda: Centipedes (carnivores). 5. Subphylum Hexapoda  Body divided into head, thorax (with 3 pairs of legs), and abdomen.  Class Insecta: Most diverse group. o Beneficial insects: Bees (pollination, honey), ladybugs (eat pests).  o Harmful insects: Mosquitoes (disease vectors), boll weevil (cotton pest). o Undergo metamorphosis: Holometabolous (complete), Hemimetabolous (incomplete). FUNCTIONS AND HABITAT  Habitat: Found in almost all environments due to adaptive diversity.  Exoskeleton: Protects and supports body; jointed for movement.  Sensory Organs: Enable detection of environmental changes.  Reproduction: Sexual; metamorphosis enhances survival. DISEASES AND ECONOMIC IMPACT 1. Vector-borne Diseases: o Mosquitoes: Malaria, Yellow Fever, Encephalitis. o Fleas: Plague. 2. Economic Importance: o Beneficial: Pollination (bees), pest control (ladybugs). o Harmful: Crop damage (boll weevil), structural damage (termites).