This MCQ module is based on: The Animal Kingdom — Major Phyla
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The Animal Kingdom — Major Phyla
🎓 Class 9
Science
CBSE
Theory
Ch 12 — Patterns in Life: Diversity and Classification
⏱ ~19 min
🌐 Language: [gtranslate]
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This assessment will be based on: The Animal Kingdom — Major Phyla
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Introduction: From Sponge to Tiger
The Animal Kingdom (Animalia) is the most varied of the five kingdoms — over 1.2 million species described, with millions still uncatalogued. All animals are multicellular eukaryotes with no cell walls and no chlorophyll. They are heterotrophs, taking in ready-made food.
To make sense of this enormous variety, zoologists divide Animalia into nine main phyla, ordered roughly from simplest to most complex. The last and most complex phylum, Chordata, is further split into vertebrate classes such as fish, amphibians, reptiles, birds and mammals. We meet each one in turn.
12.14 Phylum 1: Porifera — The Sponges
Members of Porifera are sponges — simple, mostly marine, sessile (fixed) animals. The body is full of tiny pores (ostia) through which water flows in. They have no tissues, only a loose collection of cells. They have a hard skeleton of spicules or spongin fibres. Examples: Sycon, Spongilla, Euplectella (Venus flower basket).
12.15 Phylum 2: Cnidaria (Coelenterata) — Stinging Cells
Soft-bodied aquatic animals with radial symmetry. They have a hollow body cavity (coelenteron) with a single opening that is both mouth and anus. Their tentacles carry stinging cells (cnidoblasts) used for defence and capturing prey. Examples: Hydra (freshwater), jellyfish, sea anemone, corals.
12.16 Phylum 3: Platyhelminthes — Flatworms
The first phylum to show bilateral symmetry and three germ layers (triploblastic). Their bodies are dorso-ventrally flattened (like a leaf), and many are parasitic. They have no body cavity (acoelomate). Examples: Planaria, liver fluke, tapeworm.
12.17 Phylum 4: Nematoda — Roundworms
Cylindrical, unsegmented worms with a pseudocoelom (false body cavity). Many are notorious parasites of humans and crops. Examples: Ascaris (roundworm), Wuchereria (filaria worm causing elephantiasis), pinworm, hookworm.
12.18 Phylum 5: Annelida — Segmented Worms
True coelomate animals whose bodies are divided into ring-like segments. The earthworm and leech are familiar Indian examples. They have a closed circulatory system and breathe through their moist skin. Examples: earthworm (Pheretima), leech (Hirudo), Nereis.
12.19 Phylum 6: Arthropoda — The Largest Phylum
Arthropoda is by far the biggest phylum — almost 80% of all animal species are arthropods. Common features: jointed legs, hard exoskeleton of chitin, segmented body and an open circulatory system. Examples: cockroach, butterfly, honeybee, spider, scorpion, prawn, crab, centipede.
12.20 Phylum 7: Mollusca — Soft-bodied Animals
Soft-bodied animals usually protected by a calcareous shell. They have a muscular foot for movement. Examples: snail, mussel, oyster, octopus, squid (octopus and squid have lost the external shell). Most are aquatic; some, like the garden snail, are terrestrial.
12.21 Phylum 8: Echinodermata — Spiny-Skinned
Exclusively marine animals with a spiny calcareous skin and a unique water vascular system that operates tube feet. They show radial symmetry as adults but are bilateral as larvae. Examples: starfish, sea urchin, sea cucumber, brittle star.
12.22 Phylum 9: Chordata — Animals with a Notochord
The phylum we belong to. The defining features are: a notochord (a stiff supporting rod) at some life stage, a dorsal hollow nerve cord, and pharyngeal gill slits at some stage. Most familiar chordates are vertebrates, in which the notochord is replaced by a backbone made of vertebrae.
🐾 Phyla Comparator — Click each animal to compare key features L4 Analyse
Click each of the nine illustrations to analyse its phylum on body symmetry, body cavity, segmentation and a defining trait. Use the highlights to compare across phyla.
Click any animal above to compare its phylum on body symmetry, segmentation, body cavity and key examples.
12.23 Activity — Sort Twelve Animals
Activity 12.3 — Putting Animals into Their PhylaL4 Analyse
Predict first: A snail and an octopus look very different. Should they be placed in the same phylum? Why might that be?
- List these twelve animals: jellyfish, earthworm, sponge, butterfly, snail, starfish, tapeworm, frog, snake, sparrow, dog, fish.
- For each, ask: does it have a backbone? If yes → Chordata.
- For invertebrates, look at the most striking feature: jointed legs, soft body with shell, spiny skin, segmented worm body, flat worm body, simple sac with stinging cells, porous body.
- Tabulate your phyla.
Answer key: Sponge → Porifera; Jellyfish → Cnidaria; Tapeworm → Platyhelminthes; Earthworm → Annelida; Butterfly → Arthropoda; Snail → Mollusca; Starfish → Echinodermata; Frog, Snake, Sparrow, Dog, Fish → Chordata.
Conclusion: A small set of carefully chosen features (presence of backbone, body symmetry, segmentation, body cavity, type of skeleton) is enough to assign almost any animal to one of the nine phyla.
Conclusion: A small set of carefully chosen features (presence of backbone, body symmetry, segmentation, body cavity, type of skeleton) is enough to assign almost any animal to one of the nine phyla.
12.24 The Five Vertebrate Classes
Within Phylum Chordata, the vertebrates are divided into five major classes, each with diagnostic features.
| Class | Body covering | Heart | Reproduction | Examples |
|---|---|---|---|---|
| Pisces (Fish) | Scales; gills for breathing | 2-chambered | Egg-laying, external fertilisation | Rohu, shark, Hippocampus |
| Amphibia | Moist, glandular skin | 3-chambered | Eggs in water; larva (tadpole) aquatic | Frog, toad, salamander |
| Reptilia | Dry, scaly skin | 3-chambered (4 in crocodiles) | Lay shelled eggs on land | Snake, lizard, crocodile, turtle |
| Aves (Birds) | Feathers; forelimbs as wings | 4-chambered | Lay hard-shelled eggs; warm-blooded | Sparrow, pigeon, peacock |
| Mammalia | Hair/fur; mammary glands | 4-chambered | Mostly viviparous (live young); warm-blooded | Human, dog, whale, bat |
Warm-blooded vs cold-blooded: Birds and mammals keep their body temperature constant (warm-blooded / endothermic). Fish, amphibians and reptiles cannot regulate their body temperature — it changes with the surroundings (cold-blooded / ectothermic).
Caution: Whales and bats look unusual — whales swim like fish and bats fly like birds — but both are mammals. They have hair, breathe with lungs, give birth to live young and feed them with milk.
Competency-Based Questions
In a wildlife sanctuary, a biologist sees: (i) a starfish in a tide pool, (ii) a large lizard sunning on a rock, (iii) a bat hanging in a cave, (iv) a centipede on the forest floor. She has to assign each one to its correct phylum/class.
Q1. The bat in the cave belongs to which class? L2
(c) Mammalia. Bats have hair, breathe with lungs, are warm-blooded and give birth to live young that they feed with milk — all mammalian features. Although they fly, they are not birds (no feathers).
Q2. State two features that distinguish reptiles from amphibians. L3
(i) Reptiles have a dry, scaly skin; amphibians have a moist, glandular skin. (ii) Reptiles lay hard, shelled eggs on land; amphibians lay jelly-like eggs in water and pass through an aquatic larval (tadpole) stage.
Q3. (Fill in the blank) The phylum with the largest number of species, including all insects, is ____________. L1
Arthropoda.
Q4. (True/False) All animals with a backbone are placed in the phylum Chordata, but not every chordate has a backbone. L3
True. Vertebrates are a subgroup of Chordata. The phylum also includes a few primitive chordates (like Amphioxus) that have a notochord but no proper vertebral column.
Q5. (HOT) An aquatic animal lives in the sea, has a star-shaped body with five arms, a spiny calcareous skin, and tube feet. Identify its phylum and explain how its symmetry differs as an adult versus as a larva. L4
The animal is a starfish, belonging to phylum Echinodermata. The adult shows radial symmetry (body parts arranged around a central axis), but the larva is bilaterally symmetrical. This is a clue that echinoderms evolved from bilateral ancestors.
Assertion–Reason Questions
Choose: (A) Both A and R true, R explains A · (B) Both true, R does not explain A · (C) A true, R false · (D) A false, R true
A: Sponges (Porifera) are placed at the base of the animal kingdom.
R: Sponges have neither true tissues nor organs; their body is just an aggregate of cells around water canals.
(A) Both true and R explains A. Lack of tissues and organs is the most primitive condition among animals.
A: A whale is a fish.
R: A whale lives in water and has a streamlined body.
(D) Assertion is false — whales are mammals (hair, lungs, viviparous, mammary glands). Reason is true but not enough to make an animal a fish.
A: Birds and mammals are warm-blooded.
R: Birds and mammals both have a four-chambered heart that completely separates oxygenated from deoxygenated blood.
(A) Both true and R explains A. The separation of pure oxygenated blood enables a high metabolic rate, which is needed to maintain a constant body temperature.
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