Animal Kingdom
NCERT Class 11 Biology | CBSE | NEET-UG Preparation
Study the basis of animal classification, the major non-chordate phyla, chordate characteristics and vertebrate classes. Revise important definitions, identifying features, examples and comparisons for CBSE examinations and NEET-UG.
These questions develop detailed understanding for CBSE examinations and reinforce classification concepts important for NEET-UG.
Questions
Q1. Explain the major bases used for animal classification, including organisation, symmetry, germ layers and coelom.
Q2. Describe the characteristic features of Porifera, Cnidaria and Ctenophora with examples.
Q3. Compare Platyhelminthes, Aschelminthes and Annelida with respect to body structure, body cavity and distinguishing features.
Q4. Describe the major characteristics of Arthropoda, Mollusca and Echinodermata, giving examples.
Q5. Explain the fundamental characteristics of chordates and distinguish chordates from non-chordates.
Q6. Compare Chondrichthyes and Osteichthyes.
Q7. Describe the important characteristics of Amphibia and Reptilia.
Q8. Describe the major characteristics of Aves and Mammalia.
Answers
Answer 1: Bases of animal classification
- Levels of organisation: Animals may show cellular, tissue, organ or organ-system levels.
- Symmetry: Animals may be asymmetrical, radially symmetrical or bilaterally symmetrical.
- Germ layers: Diploblastic animals develop two germ layers, whereas triploblastic animals develop three.
- Coelom: Animals may be acoelomate, pseudocoelomate or coelomate depending on the body cavity and its mesodermal lining.
- Segmentation: Repetition of body segments is prominent in annelids.
- Notochord: Its presence at some developmental stage is a defining feature of chordates.
Answer 2: Porifera, Cnidaria and Ctenophora
Porifera: Mostly aquatic animals with cellular organisation and a water canal system. Choanocytes assist water circulation and feeding. Examples include Sycon and Spongilla.
Cnidaria: Aquatic, diploblastic animals with tissue-level organisation. Cnidocytes contain nematocysts used in prey capture and defence. Examples include Hydra and Aurelia.
Ctenophora: Exclusively marine animals with eight rows of ciliated comb plates. Bioluminescence is characteristic. Examples include Pleurobrachia and Ctenoplana.
Answer 3: Platyhelminthes, Aschelminthes and Annelida
Platyhelminthes: Flat, bilaterally symmetrical, triploblastic acoelomates. Flame cells assist excretion and osmoregulation. Examples: Planaria and Taenia.
Aschelminthes: Cylindrical, unsegmented, triploblastic pseudocoelomates with a complete alimentary canal. Examples: Ascaris and Wuchereria.
Annelida: Segmented, bilaterally symmetrical, triploblastic coelomates. Nephridia assist excretion, and a closed circulatory system is generally present. Examples: Nereis and earthworm.
Answer 4: Arthropoda, Mollusca and Echinodermata
Arthropoda: The largest animal phylum, characterised by jointed appendages, a chitinous exoskeleton and an open circulatory system. Examples: cockroach and prawn.
Mollusca: Typically soft-bodied animals with a muscular foot, visceral mass and mantle. Many possess a shell and radula. Examples: Pila and Sepia.
Echinodermata: Exclusively marine animals with a calcareous endoskeleton and water vascular system. Adults generally show radial symmetry, while larvae are bilaterally symmetrical. Examples: Asterias and Echinus.
Answer 5: Chordates and non-chordates
Chordates possess a notochord, dorsal hollow nerve cord, pharyngeal gill slits and post-anal tail at least during some stage of development. An endostyle or thyroid gland is also a characteristic feature.
Non-chordates lack a notochord. Their body organisation and nervous systems vary among phyla. Chordate classification is based on the presence of the characteristic features during development, even when these features are not all visible in the adult.
Answer 6: Chondrichthyes and Osteichthyes
| Feature | Chondrichthyes | Osteichthyes |
|---|---|---|
| Endoskeleton | Cartilaginous | Primarily bony |
| Gill covering | Separate gill slits generally present | Gills generally covered by an operculum |
| Swim bladder | Absent | Usually present |
| Examples | Scoliodon, Pristis | Labeo, Catla |
Answer 7: Amphibia and Reptilia
Amphibia: They commonly inhabit aquatic and terrestrial environments. Their skin is moist and lacks scales. Respiration may involve skin, lungs and gills in larvae. The heart is usually three-chambered, and development often includes a larval stage. Examples include frogs, toads and salamanders.
Reptilia: They generally possess dry skin covered with horny scales or scutes. Respiration occurs through lungs, fertilisation is internal and the heart is usually three-chambered. Crocodilians have a four-chambered heart. Examples include lizards, snakes and turtles.
Answer 8: Aves and Mammalia
Aves: Birds possess feathers, forelimbs modified into wings and lungs supplemented by air sacs. They have a four-chambered heart and are warm-blooded. Most lay eggs. Examples include pigeons, crows and peacocks.
Mammalia: Mammals possess mammary glands and generally have hair and external ears. They breathe through lungs, have a diaphragm and possess a four-chambered heart. Most give birth to young ones, while monotremes lay eggs. Examples include humans, dogs, bats and dolphins.
Quick Revision Checklist
- Revise levels of organisation, symmetry, germ layers and coelom.
- Learn the identifying features and examples of the major non-chordate phyla.
- Memorise the fundamental features of chordates.
- Compare vertebrate classes using respiration, heart structure, skin and reproduction.
- Practise both question sets before reviewing their answers.
