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These are complete exercise solutions for Samacheer Kalvi 9th Science — Animal Kingdom. Solve each question yourself first, then verify your method and answer below. Focus on understanding the classification criteria and key distinguishing features of each group.
Key Concepts (Quick Recap)
- Classification basis: Animals are classified by presence/absence of notochord, body symmetry, coelom type, segmentation, and level of organisation.
- Invertebrates: Animals without a backbone — Porifera, Coelenterata, Platyhelminthes, Nematoda, Annelida, Arthropoda, Mollusca, Echinodermata.
- Vertebrates (Chordata): Animals with a backbone — Pisces, Amphibia, Reptilia, Aves, Mammalia.
- Body symmetry: Asymmetrical (sponges), Radial (coelenterates, echinoderms), Bilateral (all others).
- Coelom: True body cavity lined by mesoderm — present in Annelida onwards; absent in Porifera, Coelenterata, Platyhelminthes; pseudocoelom in Nematoda.
- Metamerism: Segmentation of body seen in Annelida and Arthropoda.
- Notochord: A rigid rod-like structure in chordates; replaced by vertebral column in vertebrates.
I. Choose the Correct Answer
Q1. Which phylum includes animals with pores all over the body? (a) Coelenterata (b) Porifera ✓ (c) Platyhelminthes (d) Annelida
Answer(b) ✓ — Porifera (sponges) have numerous pores (ostia) on the body surface through which water enters. The name Porifera means "pore-bearing."
Q2. The largest phylum of the animal kingdom is: (a) Mollusca (b) Annelida (c) Arthropoda ✓ (d) Chordata
Answer(c) ✓ — Arthropoda is the largest phylum, containing about 80% of all animal species. Jointed appendages and chitinous exoskeleton are their key features.
Q3. Jellyfish and hydra belong to the phylum: (a) Porifera (b) Coelenterata ✓ (c) Platyhelminthes (d) Nematoda
Answer(b) ✓ — Coelenterata (Cnidaria) includes aquatic animals with radial symmetry, tentacles with cnidoblasts (stinging cells), and a single body cavity (coelenteron).
Q4. Which of the following is a vertebrate? (a) Starfish (b) Earthworm (c) Snake ✓ (d) Snail
Answer(c) ✓ — Snake belongs to class Reptilia under phylum Chordata (vertebrates). Starfish is Echinodermata, earthworm is Annelida, snail is Mollusca — all invertebrates.
Q5. Animals with wet, slimy skin and no scales belong to class: (a) Pisces (b) Amphibia ✓ (c) Reptilia (d) Aves
Answer(b) ✓ — Amphibians have moist, glandular skin without scales. They use cutaneous respiration (skin breathing) in addition to lungs.
Q6. The phylum with segmented body (metamerism) and closed circulatory system is: (a) Arthropoda (b) Mollusca (c) Annelida ✓ (d) Nematoda
Answer(c) ✓ — Annelida shows true metamerism (segmentation) and has a closed circulatory system with dorsal and ventral blood vessels.
Q7. Which class of vertebrates has feathers and hollow bones? (a) Reptilia (b) Amphibia (c) Mammalia (d) Aves ✓
Answer(d) ✓ — Aves (birds) have feathers, pneumatic (hollow) bones, a beak with no teeth, and warm-blooded metabolism.
Q8. Tapeworm and liver fluke belong to the phylum: (a) Coelenterata (b) Platyhelminthes ✓ (c) Nematoda (d) Annelida
Answer(b) ✓ — Platyhelminthes (flatworms) are dorsoventrally flattened with bilateral symmetry. Tapeworm (Taenia) and liver fluke (Fasciola) are examples.
Q9. The animal with a water vascular system is: (a) Jellyfish (b) Earthworm (c) Starfish ✓ (d) Snail
Answer(c) ✓ — Echinodermata has a unique water vascular system (ambulacral system) used for locomotion, feeding, and respiration. Starfish (Asterias) is an example.
Q10. Ascaris belongs to the phylum: (a) Platyhelminthes (b) Nematoda ✓ (c) Annelida (d) Arthropoda
Answer(b) ✓ — Nematoda (roundworms) are cylindrical, unsegmented, bilaterally symmetrical, with a pseudocoelom. Ascaris (roundworm) is a parasitic example.
II. Fill in the Blanks
1. The phylum name Porifera means pore-bearing animals. 2. The body cavity lined by mesoderm is called the coelom. 3. Cnidoblasts (stinging cells) are the characteristic feature of Coelenterata. 4. The notochord is replaced by the vertebral column (backbone) in vertebrates. 5. Arthropods have an exoskeleton made of chitin. 6. Animals that can live on both land and water are called amphibians. 7. The water vascular system is a unique feature of the phylum Echinodermata. 8. Mammalia is the only class of vertebrates with mammary glands that produce milk. 9. The flatworms belong to the phylum Platyhelminthes. 10. Earthworm belongs to the phylum Annelida which shows true metamerism.
III. True or False
1. All invertebrates have a backbone.
AnswerFalse — Correction: Invertebrates do NOT have a backbone. Only vertebrates (Chordata) have a vertebral column.
2. Sponges (Porifera) have radial symmetry.
AnswerFalse — Correction: Most sponges are asymmetrical; some show radial symmetry but they are generally classified as asymmetrical.
3. Coelenterates have a single body cavity called the coelenteron.
AnswerTrue — Coelenterates have a sac-like body plan with a single opening (mouth) that serves as both inlet and outlet, and a central cavity called the coelenteron.
4. Platyhelminthes are triploblastic animals.
AnswerTrue — Flatworms develop from three germ layers (ectoderm, mesoderm, endoderm) and are triploblastic, though they lack a true coelom (they are acoelomate).
5. Arthropods have an open circulatory system.
AnswerTrue — Arthropods have an open circulatory system where blood flows through body cavities (haemocoel), not enclosed in blood vessels.
6. Molluscs have an exoskeleton made of chitin.
AnswerFalse — Correction: Molluscs have a calcareous shell (made of calcium carbonate). The chitinous exoskeleton is characteristic of Arthropoda.
7. All vertebrates are warm-blooded.
AnswerFalse — Correction: Only birds (Aves) and mammals (Mammalia) are warm-blooded (homeothermic). Fish, amphibians, and reptiles are cold-blooded (poikilothermic).
8. Fishes breathe through gills.
AnswerTrue — Pisces respire through gills which extract dissolved oxygen from water.
9. Amphibians can breathe through their skin.
AnswerTrue — Adult amphibians respire through lungs and moist skin (cutaneous respiration).
10. Reptiles have a three-chambered heart (except crocodiles).
AnswerTrue — Most reptiles have a three-chambered heart (two atria + one ventricle). Crocodiles are the exception with a four-chambered heart.
IV. Match the Following
Set 1: Phyla and Their Key Features
| Column I (Phylum) | Column II (Feature) |
|---|
| 1. Porifera | (d) Pores (ostia) on body surface |
| 2. Coelenterata | (e) Cnidoblasts (stinging cells) |
| 3. Platyhelminthes | (a) Dorsoventrally flattened body |
| 4. Nematoda | (f) Pseudocoelom, unsegmented round body |
| 5. Annelida | (b) Metamerism (true segmentation) |
| 6. Arthropoda | (c) Jointed appendages and chitinous exoskeleton |
| 7. Mollusca | (h) Muscular foot and calcareous shell |
| 8. Echinodermata | (g) Water vascular system and spiny skin |
Set 2: Vertebrate Classes and Characteristics
| Column I (Class) | Column II (Characteristic) |
|---|
| 1. Pisces | (d) Gills for respiration, scales on body |
| 2. Amphibia | (e) Moist skin, lives in water and land |
| 3. Reptilia | (a) Dry scaly skin, lay eggs on land |
| 4. Aves | (c) Feathers, hollow bones, warm-blooded |
| 5. Mammalia | (b) Mammary glands, hair, warm-blooded |
V. Short Answers
Q1. What is the basis of classification of animals?
Answer
Animals are classified based on the following features: 1. Presence or absence of notochord — Chordates vs Non-chordates 2. Body symmetry — Asymmetrical, Radial, Bilateral 3. Number of germ layers — Diploblastic (2 layers) or Triploblastic (3 layers) 4. Type of body cavity (coelom) — Acoelomate, Pseudocoelomate, Coelomate 5. Segmentation (metamerism) — Present or absent 6. Level of organisation — Cellular, Tissue, Organ, Organ-system level
Q2. Differentiate between invertebrates and vertebrates.
Answer
| Feature | Invertebrates | Vertebrates |
|---|
| Backbone | Absent | Present |
| Notochord | Absent | Present (replaced by vertebral column) |
| Body size | Generally small | Generally larger |
| % of animals | ~97% of species | ~3% of species |
| Examples | Sponge, jellyfish, earthworm, insect, snail, starfish | Fish, frog, lizard, bird, mammal |
Q3. List the salient features of Porifera.
Answer
1. Pore-bearing animals with numerous ostia (inlet pores) and osculum (outlet). 2. Body is asymmetrical or radially symmetrical. 3. Cellular level of organisation (no true tissues). 4. Body has a skeleton of spicules (calcareous or siliceous) or spongin fibres. 5. Aquatic, mostly marine, sessile (fixed to a surface). 6. Water enters through ostia and exits through osculum — helps in filter feeding and respiration. 7. Examples: Sycon (scypha), Spongilla (freshwater sponge), Euspongia (bath sponge).
Q4. Describe the phylum Coelenterata (Cnidaria).
Answer
1. Radial symmetry and diploblastic (two germ layers: ectoderm and endoderm with mesoglea in between). 2. Body has a single cavity called coelenteron with a single opening (mouth/anus). 3. Possess cnidoblasts (stinging cells) on tentacles for defence and capturing prey. 4. Two body forms: Polyp (sessile, cylindrical — e.g., Hydra) and Medusa (free-swimming, umbrella-shaped — e.g., Jellyfish). 5. Some show alternation of generations (polyp and medusa stages alternate). 6. Mostly marine; a few freshwater. 7. Examples: Hydra, Jellyfish (Aurelia), Sea anemone, Coral.
Q5. What are the distinguishing features of Annelida?
Answer
1. Segmented body (true metamerism) — body divided into similar segments (metameres). 2. Triploblastic and coelomate (true body cavity). 3. Closed circulatory system with dorsal and ventral blood vessels. 4. Nephridia for excretion. 5. Locomotion by setae (bristles) or parapodia (lateral appendages). 6. May be aquatic (leech) or terrestrial (earthworm). 7. Examples: Earthworm (Lumbricus), Leech (Hirudinaria), Nereis.
Q6. Compare Arthropoda and Mollusca.
Answer
| Feature | Arthropoda | Mollusca |
|---|
| Body covering | Chitinous exoskeleton | Calcareous shell (external or internal) |
| Body division | Head, thorax, abdomen | Head, muscular foot, visceral mass |
| Appendages | Jointed (arthropodia) | Muscular foot (not jointed) |
| Circulatory system | Open | Open (except Cephalopoda) |
| Examples | Crab, butterfly, spider | Snail, octopus, oyster |
| Largest phylum? | Yes (80% species) | Second largest |
VI. Detailed Answers
Q1. Describe the classification of invertebrates with key features and examples of each phylum.
Answer
| Phylum | Symmetry | Germ Layers | Coelom | Key Feature | Examples |
|---|
| Porifera | Asymmetrical/Radial | Cellular level | Absent | Pores (ostia), spicules | Sycon, Spongilla, Euspongia |
| Coelenterata | Radial | Diploblastic | Absent | Cnidoblasts, coelenteron | Hydra, Jellyfish, Sea anemone |
| Platyhelminthes | Bilateral | Triploblastic | Acoelomate | Flat body, flame cells | Tapeworm, Liver fluke, Planaria |
| Nematoda | Bilateral | Triploblastic | Pseudocoelom | Round cylindrical body | Ascaris, Wuchereria, Pinworm |
| Annelida | Bilateral | Triploblastic | Coelomate | Metamerism, nephridia | Earthworm, Leech, Nereis |
| Arthropoda | Bilateral | Triploblastic | Coelomate | Jointed appendages, chitin exoskeleton | Crab, Butterfly, Spider, Millipede |
| Mollusca | Bilateral | Triploblastic | Reduced coelom | Muscular foot, calcareous shell | Snail, Octopus, Oyster, Squid |
| Echinodermata | Radial (adult) | Triploblastic | Coelomate | Water vascular system, spiny skin | Starfish, Sea urchin, Sea cucumber |
Q2. Describe the classes of Chordata (vertebrates) with key features and examples.
Answer
| Class | Habitat | Skin | Respiration | Heart | Reproduction | Examples |
|---|
| Pisces (Fish) | Aquatic | Scales (dermal) | Gills | 2-chambered | Oviparous (lay eggs in water) | Shark, Rohu, Catla |
| Amphibia | Water + Land | Moist, glandular, no scales | Gills (larva), Lungs + Skin (adult) | 3-chambered | Oviparous (eggs in water) | Frog, Toad, Salamander |
| Reptilia | Mostly land | Dry, scaly | Lungs | 3-chambered (4 in crocodiles) | Oviparous (amniotic eggs on land) | Lizard, Snake, Crocodile, Turtle |
| Aves (Birds) | Aerial/Land | Feathers | Lungs + air sacs | 4-chambered | Oviparous (hard-shelled eggs) | Pigeon, Sparrow, Eagle, Ostrich |
| Mammalia | Land/Aquatic | Hair/fur, sweat/sebaceous glands | Lungs | 4-chambered | Viviparous (most); Oviparous (Platypus, Echidna) | Human, Bat, Whale, Kangaroo |
Key distinguishing features:
1. Pisces: Streamlined body, fins (paired and unpaired), lateral line sensory organ, internal gills covered by operculum (bony fish) or exposed (cartilaginous fish). Cold-blooded.
2. Amphibia: Dual life — larval stage (tadpole) in water with gills and tail; adult on land with lungs and four limbs. Moist skin aids cutaneous respiration. Hibernate in winter and aestivate in summer.
3. Reptilia: Dry scaly skin prevents water loss — truly terrestrial. Amniotic egg with leathery shell can be laid on land. Most have three-chambered heart; crocodiles have four chambers. Cold-blooded.
4. Aves: Light, hollow (pneumatic) bones for flight. Feathers provide insulation and aerodynamic surface. Beak (no teeth). Four-chambered heart. Warm-blooded. High metabolic rate. Streamlined body.
5. Mammalia: Mammary glands produce milk for young. Hair/fur on body. External ear (pinna). Four-chambered heart. Warm-blooded. Most are viviparous (live birth); exceptions: Platypus and Echidna (oviparous). Different types of teeth (heterodont dentition).
Q3. Compare Pisces and Amphibia in detail.
Answer
| Feature | Pisces | Amphibia |
|---|
| Habitat | Exclusively aquatic | Both water and land (dual life) |
| Skin | Covered with scales (dermal) | Moist, glandular, no scales |
| Respiration | Gills (internal) | Gills (larva), Lungs + Skin (adult) |
| Limbs | Fins (paired: pectoral, pelvic; unpaired) | Four limbs (no fins in adult) |
| Heart | 2-chambered (1 atrium + 1 ventricle) | 3-chambered (2 atria + 1 ventricle) |
| Eggs | Lay eggs in water, external fertilisation | Lay eggs in water, mostly external fertilisation |
| Lateral line | Present (detects water currents) | Absent in adult |
| Body temperature | Cold-blooded | Cold-blooded |
| Examples | Shark, Rohu, Catla, Tuna | Frog, Toad, Salamander, Newt |
Q4. Explain the significance of the water vascular system in Echinodermata.
Answer
The water vascular system (also called the ambulacral system) is a unique feature of Echinodermata. It is a network of water-filled canals used for:
1. Locomotion: Tube feet (podia) extend and contract using hydraulic pressure from the water vascular system, enabling slow movement. 2. Feeding: Tube feet help capture and manipulate food particles. 3. Respiration: Gas exchange occurs through the thin walls of tube feet. 4. Sensory function: Tube feet have sensory cells that detect chemical and mechanical stimuli.
Structure: Seawater enters through the madreporite (a calcareous plate), passes through the stone canal, ring canal, radial canals, and lateral canals to reach the tube feet.
Common Mistakes
1. Calling all invertebrates "worms" — Worms belong to three different phyla: Platyhelminthes (flatworms), Nematoda (roundworms), and Annelida (segmented worms). They differ in body plan, coelom type, and segmentation.
2. Confusing coelom types — Acoelomate (no body cavity — Porifera, Coelenterata, Platyhelminthes), Pseudocoelomate (false cavity not fully lined by mesoderm — Nematoda), Coelomate (true cavity lined by mesoderm — Annelida onwards).
3. Saying all chordates are vertebrates — All vertebrates are chordates, but not all chordates are vertebrates. Protochordates (e.g., Balanoglossus, Amphioxus) have a notochord but no vertebral column.
4. Confusing symmetry types — Radial symmetry (body can be divided into similar halves along any plane through the central axis — Coelenterata, Echinodermata adults) vs Bilateral symmetry (body can be divided into mirror halves along one plane — most animals).
5. Forgetting that echinoderm larvae are bilaterally symmetrical — Adult echinoderms show radial (pentamerous) symmetry, but their larvae are bilaterally symmetrical. This is evidence of their bilaterian ancestry.
6. Confusing open and closed circulatory systems — Arthropoda and Mollusca have an open system (blood flows through haemocoel). Annelida and Chordata have a closed system (blood flows through blood vessels).
7. Listing only one distinguishing feature per phylum — Each phylum has multiple key features. For example, Arthropoda = jointed appendages + chitinous exoskeleton + segmented body + open circulation. List at least 2-3 features for full marks.
Exam Checklist
- [ ] Basis of animal classification: symmetry, germ layers, coelom, notochord, segmentation
- [ ] All 8 invertebrate phyla — key feature + 2 examples each memorised
- [ ] Invertebrate vs vertebrate comparison table
- [ ] All 5 vertebrate classes — habitat, skin, respiration, heart chambers, examples
- [ ] Pisces vs Amphibia comparison (common exam question)
- [ ] Reptilia vs Aves comparison
- [ ] Aves vs Mammalia comparison
- [ ] Water vascular system of Echinodermata — structure and functions
- [ ] Cnidoblasts and their function in Coelenterata
- [ ] Coelom types: acoelomate, pseudocoelomate, coelomate — with phylum examples
- [ ] Cold-blooded vs warm-blooded animals — which classes belong where
- [ ] Common mistakes: chordates vs vertebrates, symmetry types, coelom confusion
Internal Links
- [Animal Kingdom Guide](/school/tamil-nadu-state-board/class/9/science/animal-kingdom)
- [All Class 9 Science Solutions](/school/tamil-nadu-state-board/class/9/science/solutions)
- [Class 9 Science Subject Guide](/school/tamil-nadu-state-board/class/9/science)
