GENERAL INTRODUCTION-
All members of kingdom animalia is multicellular.
BASIS OF CLASSIFICATION–
There are many basis of classification as given below-
- Classification based of level of organization–
- Level of Organization- An organization made up of single cell which can perform all life activities.(ex.- Sponges)
- Tissue Level of Organization- Many cells perform a same function, which combine to form a tissue.
- Organ Level of Organization- Many tissues are grouped to form an organ. Each organ specialised for a particular function.
- Organ System Level of Organization- Many organ combine to form organ system.
- Classification based on type of circulatory system–
- Open Type- Blood flow freely in body cavity.
- Closed Type- Blood flow in body cavities such as arteries, veins and capillaries.
- Classification based on Symmetry-
- Asymmetry- Any plane which passed through the center, then it does not divided into equal halves.
- Radial symmetry- Any plane which passed through the center, then it divided into equal halves.
- Bilateral symmetry- Only plane which passed through the center, then it divided in only 2 halves i.e. right and left.
- Classification based on diploblastic and triploblastic–
- Diploblastic- The cells are arrange in 2 embryonic layers i.e. ectoderm is outer layer and endoderm is inner layer.
- Triploblastic- The cells are arrange in 3 embryonic layers i.e. ectoderm is outer layer, mesoderm is middle layer(or present between both 2) and endoderm is inner layer.
- Classification based on coelom-
- coelom- It is a body cavity which lined by mesoderm.
- Coelomates- Those animal which possess coelom.
- Acoelomates- Those animal which not possess coelom.
- Pseudocoelom- It is a body cavity which completely covered by mesodermal layer. This cavity present between ectoderm and endoderm.
- Pseudocoelomate- Those animal possess pseudocoelom.
- Acoelomates- Those animal in which the body cavity is absent.
- Classification based on segmentation-
- Segmentation- The dividing of body into repeated sections or segments. Each segments may have its own structure and function, helping with movement, flexibility. ex- earthworm
- Metameric segmentation- Body divided into repeated segments, both externally and internally. This phenomenon is called metamerism.
- Classification based on notochord-
- Notochord- It is a flexible, rod-like structure in embryonic stages, providing support and forming the backbone.
- Chordates- Those animal which shows notochord.
- Non-Chordates- Those animal which not shows notochord.
CLASSIFICATION OF ANIMALS-
Phylum: Porifera (Sponges)
- General Features:
- Commonly called sponges.
- Mostly marine and asymmetrical.
- Primitive multicellular animals with cellular level of organization.
- Body has a canal system for water flow:
Ostia → Spongocoel → Osculum.- Purpose: Food gathering, respiration, and waste removal.
- Choanocytes (collar cells): Line the spongocoel and canals; aid in intracellular digestion.
- Skeleton: Made of spicules or spongin fibers.
- Reproduction:
- Asexual: Fragmentation.
- Sexual: Internal fertilization; hermaphroditic (both eggs and sperm in one individual).
- Development: Indirect with distinct larval stages.
- Examples: Sycon (Scypha), Spongilla (freshwater sponge), Euspongia (bath sponge).
Phylum: Coelenterata (Cnidaria)
- General Features:
- Aquatic, mostly marine, radially symmetrical.
- Cnidoblasts: Specialized cells containing nematocysts (stinging capsules) for defense and prey capture.
- Tissue level of organization; diploblastic.
- Gastrovascular cavity with a single opening (mouth).
- Digestion: Both extracellular and intracellular.
- Skeleton: In corals, made of calcium carbonate.
- Body Forms:
- Polyp: Sessile, cylindrical (e.g., Hydra, Adamsia).
- Medusa: Free-swimming, umbrella-shaped (e.g., Aurelia).
- Metagenesis: Alternation between polyp (asexual) and medusa (sexual).
- Examples: Physalia (Portuguese man-of-war), Adamsia (Sea anemone), Gorgonia (Sea-fan), Meandrina (Brain coral).
Phylum: Ctenophora (Comb Jellies)
- General Features:
- Exclusively marine, radially symmetrical, diploblastic.
- Ciliated comb plates: For locomotion.
- Bioluminescence: Emit light naturally.
- Digestion: Both extracellular and intracellular.
- Reproduction: Sexual, external fertilization, indirect development.
- Examples: Pleurobrachia, Ctenoplana.
Phylum: Platyhelminthes (Flatworms)
- General Features:
- Dorsoventrally flattened body, bilaterally symmetrical.
- Triploblastic, acoelomate, organ-level organization.
- Many are endoparasites (e.g., Taenia in humans).
- Flame cells: For excretion and osmoregulation.
- Reproduction:
- Hermaphroditic; internal fertilization.
- Development involves multiple larval stages.
- Regeneration: Seen in Planaria.
- Examples: Taenia (Tapeworm), Fasciola (Liver fluke).
Phylum: Aschelminthes (Roundworms)
- General Features:
- Round body in cross-section; bilaterally symmetrical, pseudocoelomate.
- Organ-system level of organization.
- Alimentary canal: Complete with a muscular pharynx.
- Excretion through excretory pores.
- Dioecious: Separate sexes; internal fertilization.
- Development: Direct or indirect.
- Examples: Ascaris (Roundworm), Wuchereria (Filarial worm), Ancylostoma (Hookworm).
Phylum: Annelida (Segmented Worms)
- General Features:
- Found in aquatic and terrestrial habitats; some are parasitic.
- Bilaterally symmetrical, triploblastic, coelomate.
- Segmented body (metamerism) aids movement.
- Locomotion: Muscular movement; aquatic forms like Nereis have parapodia for swimming.
- Circulatory System: Closed type.
- Excretion: Nephridia.
- Nervous System: Paired ganglia, double ventral nerve cord.
- Reproduction: Dioecious (e.g., Nereis) or hermaphroditic (e.g., Earthworm).
- Examples: Nereis, Pheretima (Earthworm), Hirudinaria (Leech).
Phylum: Arthropoda
- General Features:
- Largest phylum; over 2/3rd of all species.
- Bilaterally symmetrical, segmented, coelomate.
- Chitinous exoskeleton; body divided into head, thorax, and abdomen.
- Jointed appendages for movement.
- Respiration through gills, book gills, book lungs, or tracheae.
- Open circulatory system.
- Excretion: Malpighian tubules.
- Reproduction: Dioecious; internal fertilization.
- Examples:
- Economically important: Apis (Honeybee), Bombyx (Silkworm).
- Vectors: Anopheles (Malaria mosquito).
- Pest: Locusta (Locust).
- Living fossil: Limulus (King crab).
Additional Tips for Competitive Exams:
- Classification Mnemonics: Use acronyms to remember phylum examples.
Example: “SAP” for Porifera (Sycon, Spongilla, Euspongia). - Diagram Practice: Draw labeled diagrams of structures like choanocytes, nematocysts, and comb plates.
- Key Features Comparisons: Create tables to compare symmetry, coelom type, and reproduction between phyla.
- Larval Stages: Remember larval forms for indirect development (e.g., trochophore in annelids).
- Unique Features Highlight:
- Bioluminescence (Ctenophora).
- Metagenesis (Cnidaria).
- Parapodia (Annelida).
Phylum – Mollusca
- Size and Habitat: Mollusca is the second-largest phylum. Members can be found in both terrestrial and aquatic habitats (marine and freshwater).
- Body Characteristics:
- Symmetry and Organization: Bilateral symmetry, triploblastic (three layers of tissue), and coelomate (having a body cavity).
- Body Parts: They have a soft body covered by a calcareous shell, with a head, muscular foot, and a visceral hump. A mantle (soft skin layer) covers the visceral hump, and the mantle cavity contains feather-like gills.
- Sensory Tentacles: The head region has sensory tentacles.
- Radula: A rasping organ used for feeding, like a file, inside the mouth.
- Reproduction: They are dioecious (separate sexes) and oviparous (egg-laying). Their development is indirect (larval stage before becoming adult).
- Examples: Pila (Apple snail), Octopus, Cuttlefish, Squid.
Phylum – Echinodermata
- Body Characteristics: Echinoderms have an endoskeleton made of calcareous ossicles (internal, spiny skeleton).
- Symmetry and Circulatory System: Adult echinoderms are radially symmetrical, while larvae are bilaterally symmetrical. They have a water vascular system, which helps with movement, food capture, and respiration. They lack an excretory system.
- Reproduction: They have separate sexes, and fertilization is usually external with indirect development (free-swimming larvae).
- Examples: Starfish, Sea urchins, Sea cucumber.
Phylum – Hemichordata
- Structure: Hemichordates are worm-like marine animals. They have a stomochord (similar to notochord) in the collar region. Their body is divided into three parts: proboscis, collar, and trunk.
- Circulatory and Respiratory Systems: They have an open circulatory system and respire through gills.
- Reproduction: Sexual reproduction with external fertilization and indirect development.
- Examples: Balanoglossus, Saccoglossus.
Phylum – Chordata
- Characteristics: All chordates have a notochord, dorsal hollow nerve cord, and pharyngeal gill slits.
- Body Parts: They have a post-anal tail and a closed circulatory system.
- Subphyla:
- Urochordata (Tunicata): Notochord only in the larval stage.
- Cephalochordata: Notochord persists throughout life.
- Vertebrata: Vertebrates have a backbone (vertebral column). Their heart is muscular and ventral (on the belly side).
- Vertebrates also have kidneys for excretion and osmoregulation, paired appendages (fins or limbs).
- Classes in Vertebrates:
- Cyclostomata (Jawless fish): Example – Lamprey. They are parasitic and have a circular sucking mouth.
- Chondrichthyes (Cartilaginous fishes): Example – Sharks. They have cartilaginous skeletons, separate gill slits, and powerful jaws.
- Osteichthyes (Bony fishes): Example – Fish like Catla and Betta. They have bony skeletons and covered gills.
- Amphibia: Example – Frogs. They can live both in water and on land. They have a moist skin and three-chambered heart.
- Reptilia: Example – Crocodiles. They are terrestrial, with dry skin and are cold-blooded (poikilotherms).
- Aves (Birds): Example – Crow. They have feathers, wings, and a four-chambered heart.
- Mammalia: Example – Tiger. They produce milk, have hair, and mostly give birth to live young (viviparous).
Summary of Phyla
- Porifera: Multicellular animals with a cellular level of organization and flagellated choanocytes (collar cells).
- Cnidaria: Aquatic, with tentacles and cnidoblasts (stinging cells).
- Ctenophora: Marine animals with comb plates for locomotion.
- Platyhelminthes: Flat-bodied animals, often parasitic, with bilateral symmetry.
- Aschelminthes: Roundworms, with a pseudocoelom (false body cavity).
- Annelida: Segmented worms with a true coelom.
- Arthropoda: Jointed appendages, largest animal group.
- Mollusca: Soft body with a calcareous shell.
- Echinodermata: Spiny skin with a water vascular system.
- Hemichordata: Worm-like with a proboscis, collar, and trunk.
- Chordata: Animals with a notochord, nerve cord, and pharyngeal gill slits.
Important Characteristics to Identify Phyla
- Symmetry: Radial (Echinodermata), Bilateral (Chordata, Mollusca, Arthropoda, etc.).
- Coelom: True coelom in many phyla like Mollusca, Annelida, Echinodermata, Chordata.
- Segmentation: Present in Annelida, Arthropoda.
- Exoskeleton: Arthropoda, Mollusca, Chordata (vertebrates).
- Respiration: Gills (in aquatic species), lungs (in terrestrial vertebrates), skin (Amphibians).
This summary helps clarify the distinct characteristics of each phylum in the Animal Kingdom. Understanding these basic differences is crucial for competitive exams like NEET, UPSC, or other biology-related tests.
These all are the notes of chapter 4 in biology. And important questions are below HERE. *#THANKS FOR VISITING, VISIT AGAIN#*😊
Q1: What is a cellular level of organization?
A1: It is when an organism is made up of a single cell that performs all life activities. Example: Sponges.
Q2: What is the tissue level of organization?
A2: It is when many cells perform the same function and combine to form a tissue.
Q3: What is the organ level of organization?
A3: It is when tissues group together to form an organ, each specialized for a specific function.
Q4: What is the organ system level of organization?
A4: It is when multiple organs combine to form an organ system that performs complex body functions.
Classification Based on the Circulatory System
Q5: What is an open circulatory system?
A5: Blood flows freely in the body cavity without specific blood vessels.
Q6: What is a closed circulatory system?
A6: Blood flows through vessels like arteries, veins, and capillaries.
Classification Based on Symmetry
Q7: What is asymmetry?
A7: When an organism cannot be divided into equal halves by any plane passing through the center. Example: Sponges.
Q8: What is radial symmetry?
A8: When any plane passing through the center divides the organism into equal halves. Example: Starfish.
Q9: What is bilateral symmetry?
A9: When only one plane divides the organism into two equal halves (right and left). Example: Humans.
Classification Based on Germ Layers
Q10: What are diploblastic animals?
A10: Animals with two embryonic layers: ectoderm (outer layer) and endoderm (inner layer). Example: Jellyfish.
Q11: What are triploblastic animals?
A11: Animals with three embryonic layers: ectoderm, mesoderm (middle layer), and endoderm. Example: Earthworms.
Classification Based on Body Cavity (Coelom)
Q12: What is a coelom?
A12: A body cavity lined by mesoderm.
Q13: What are coelomates?
A13: Animals with a true coelom. Example: Humans.
Q14: What are acoelomates?
A14: Animals without a body cavity. Example: Flatworms.
Q15: What is a pseudocoelom?
A15: A body cavity not fully lined by mesoderm, present between ectoderm and endoderm. Example: Roundworms.
Classification Based on Segmentation
Q16: What is segmentation?
A16: Division of the body into repeated sections or segments, helping with movement. Example: Earthworms.
Q17: What is metameric segmentation?
A17: When the body is divided into segments both externally and internally. This is called metamerism.
Classification Based on Notochord
Q18: What is a notochord?
A18: A flexible rod-like structure present in the embryonic stage, giving support to the body.
Q19: What are chordates?
A19: Animals with a notochord. Example: Humans.
Q20: What are non-chordates?
A20: Animals without a notochord. Example: Insects.
Examples of Phyla
Q21: Name an example of Porifera (sponges).
A21: Sycon (Scypha).
Q22: Name an example of Cnidaria.
A22: Hydra, Jellyfish (Aurelia).
Q23: Name an example of Platyhelminthes (flatworms).
A23: Taenia (Tapeworm).
Q24: Name an example of Annelida.
A24: Earthworm (Pheretima).
Q25: Name an example of Arthropoda.
A25: Honeybee (Apis).
Q26: Name an example of Mollusca.
A26: Octopus, Snail (Pila).
Q27: Name an example of Echinodermata.
A27: Starfish.
Q28: Name an example of Hemichordata.
A28: Balanoglossus.
Q29: Name an example of Chordata.
A29: Tiger (Mammalia), Frog (Amphibia).