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Non-Chordate Phyla and Examples ICSE Class 9 Biology

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BiologyICSE Class 9 · Diversity in the Animal Kingdom

Non-Chordate Phyla: Porifera, Cnidaria, Worms, Arthropoda, Mollusca and Echinodermata (ICSE Class 9 Biology)

Updated 17 October 2026 · Fact-checked

Non-chordates have no notochord. The main phyla are Porifera (pores, sponges), Cnidaria (stinging cells, Hydra), Platyhelminthes (flatworms), Nematoda (round worms), Annelida (segmented worms), Arthropoda (jointed legs), Mollusca (soft body, usually a shell) and Echinodermata (spiny skin, tube feet).

Understand Non-Chordate Phyla: Porifera to Echinodermata

1. Basis of classification. Animals are first grouped by whether a notochord is present (chordates) or absent (non-chordates), then by body symmetry, number of cell layers, body cavity, segmentation and appendages.

2. Porifera. Pore-bearing, mostly marine, fixed (sessile) animals with a body wall of two cell layers, a central cavity (spongocoel) and a skeleton of spicules or spongin; water enters through many small pores and leaves through the osculum. Examples: *Sycon*, *Spongilla*, bath sponge.

3. Cnidaria (Coelenterata). Radially symmetrical, two cell layers (diploblastic) with a single opening for the mouth and anus; tentacles carry stinging cells (cnidoblasts). Examples: *Hydra*, *Obelia*, jellyfish, sea anemone.

4. The worms.

  • *Platyhelminthes*: flat, unsegmented, bilaterally symmetrical, no true body cavity; many are parasites. Examples: *Planaria*, tapeworm (*Taenia*), liver fluke.
  • *Nematoda*: long, round, unsegmented worms with a complete digestive tract. Examples: *Ascaris*, hookworm, filarial worm.
  • *Annelida*: body divided into rings (segments), with a true body cavity, bristles and a closed circulatory system. Examples: earthworm, leech, *Nereis*.

5. Arthropoda. The largest phylum: jointed legs, hard exoskeleton of chitin, segmented body. Insects have three pairs of legs, spiders four, crabs and prawns five (including claws). Examples: cockroach, butterfly, spider, scorpion, prawn.

6. Mollusca. Soft unsegmented body, a muscular foot and usually a shell. Examples: snail (*Pila*), mussel (*Unio*), octopus, squid.

7. Echinodermata. Marine, spiny skin, radial symmetry (in adults) and tube feet for movement. Examples: starfish, sea urchin, sea cucumber.

Non-Chordate Phyla: Porifera to Echinodermata: key facts

Sponges
  • Porifera
  • Pores and osculum
  • Spicules or spongin
  • Examples Sycon, Spongilla
Stinging animals
  • Cnidaria
  • Cnidoblasts
  • Two layers
  • Examples Hydra, jellyfish
Worms
FlatwormPlanaria, Taenia
RoundwormAscaris
Segmented wormearthworm, leech
Others
Arthropodajointed legs
Molluscasoft body, foot
Echinodermataspiny skin, tube feet

Non-Chordate Phyla: Porifera to Echinodermata in real life

The idea, met in an everyday situation. Answer the question in your own words, then compare with the model answer. The one-line hook is what to remember.

Sorting a market haul

Suppose a fish market has prawns, a squid, a starfish, a clump of sponge and a leech picked up from the water.

Place each in its phylum.

Try it first, then show the solutionSolution
  1. Prawn has jointed legs and a chitin exoskeleton: Arthropoda.
  2. Squid has a soft body and foot: Mollusca.
  3. Starfish has spiny skin and tube feet: Echinodermata.
  4. Sponge has pores: Porifera.
  5. Leech has a segmented body: Annelida.

Answer: Arthropoda, Mollusca, Echinodermata, Porifera, Annelida.

Memory hook: Look at legs, shell, spines, pores, rings.

Tricks to remember Non-Chordate Phyla: Porifera to Echinodermata

Short memory aids. Say each one aloud once, then use it on a question the same day.

  • PCPNAAME

    Porifera, Cnidaria, Platyhelminthes, Nematoda, Annelida, Arthropoda, Mollusca, Echinodermata.

    Use it when: Order of phyla.

  • Nema = thread

    Nematodes are thread-like round worms.

    Use it when: Nematoda.

Non-Chordate Phyla: Porifera to Echinodermata: solved examples

Ordered from board level to HOTS. Try each one before you open the solution.

Example 1: Odd one out · 2 marks · Very short answerBoard level

Odd one out: Hydra, jellyfish, sea anemone, starfish. Give a reason. [2]

Try it first, then show the solutionSolution
  1. Starfish is an echinoderm.
  2. The others are cnidarians.

Answer: Starfish, because it is an echinoderm while the others are cnidarians.

Example 2: Annelid versus nematode · 3 marks · Short answerHarder board level

Give three differences between an earthworm and Ascaris. [3]

Try it first, then show the solutionSolution
  1. Body: earthworm is divided into segments; Ascaris is unsegmented.
  2. Shape: earthworm is cylindrical with bristles; Ascaris is smooth and round, tapered at the ends.
  3. Mode of life: earthworm is free-living; Ascaris is a parasite in the human intestine.

Answer: The earthworm is segmented and free-living with bristles; Ascaris is unsegmented and parasitic.

Example 3: Porifera adaptation · 3 marks · Short answerHarder board level

A sponge cannot move yet it feeds. Explain how it obtains food and why it is called a sessile animal. [3]

Try it first, then show the solutionSolution
  1. Water enters through pores and flows through the central cavity.
  2. Food particles and oxygen are taken from the water current.
  3. It is fixed to a rock, so it is sessile.

Answer: It filters food from the water that enters through pores and leaves through the osculum.

Example 4: Arthropod ID · 4 marks · Case-basedHarder board level

A specimen has 8 legs, a body in two parts and no antennae. (i) Which class of arthropod is it? [1] (ii) Name an example. [1] (iii) Why is it not an insect? [2]

Try it first, then show the solutionSolution
  1. (i) Arachnid.
  2. (ii) Spider or scorpion.
  3. (iii) Insects have three pairs of legs, a three-part body and antennae.

Answer: (i) Arachnid (ii) Spider (iii) It has four pairs of legs and no antennae.

Example 5: Classify the unknown · 5 marks · Case-basedHOTS / competency

A student describes an animal: soft body, no segments, a muscular foot, a coiled shell, lives in a pond. (i) Name the phylum. [1] (ii) Name two other animals of this phylum with different body plans. [2] (iii) Explain why it is placed apart from annelids. [2]

Try it first, then show the solutionSolution
  1. (i) Mollusca.
  2. (ii) Octopus (no external shell) and mussel (two shells).
  3. (iii) Annelids have a segmented body and bristles; molluscs are unsegmented.

Answer: (i) Mollusca (ii) Octopus, mussel (iii) Annelids are segmented; molluscs are not.

Where students lose marks in Non-Chordate Phyla: Porifera to Echinodermata

The slips examiners see most often, and what to write instead.

  • Mistake: Writing that sponges have tentacles

    Cnidaria are confused with Porifera.

    Do this: Sponges have pores; cnidarians have tentacles.

    Usually costs: 1 mark.

  • Mistake: Stating that all worms are annelids

    Three phyla are called worms.

    Do this: Name flatworm, roundworm and segmented worm separately.

    Usually costs: 1 mark.

  • Mistake: Calling a spider an insect

    Legs are not counted.

    Do this: Insects have 3 pairs of legs; spiders have 4.

    Usually costs: 1 mark.

Exam tips

  • Learn one distinguishing feature and two examples per phylum.
  • Use tables with phylum, features and example.
  • For parasites, name the host.
  • Mention symmetry where relevant.

Practice questions on Non-Chordate Phyla: Porifera to Echinodermata

Write each answer on paper first. Open the hint only if you are stuck, and the answer only when you have finished.

  1. Q1 · 1 mark · MCQBoard level

    Which phylum has stinging cells?
    (a) Porifera
    (b) Cnidaria
    (c) Annelida
    (d) Mollusca

    Hint

    Cnidoblast.

    Answer

    (b) Cnidaria.

  2. Q2 · 2 marks · Very short answerBoard level

    Name the largest phylum of animals and state one feature. [2]

    Hint

    Jointed legs.

    Answer

    Arthropoda; it has jointed legs and a chitin exoskeleton.

  3. Q3 · 2 marks · Very short answerBoard level

    Where do the tube feet of echinoderms help the animal? [2]

    Hint

    Movement.

    Answer

    They help in movement and in holding food or prey.

  4. Q4 · 1 mark · Assertion-reasonHarder board level

    Assertion (A): A tapeworm has no digestive tract.
    Reason (R): It absorbs digested food from the host intestine.
    (a) Both A and R are true and R is the correct explanation of A.
    (b) Both A and R are true but R is not the correct explanation of A.
    (c) A is true but R is false.
    (d) A is false but R is true.

    Hint

    Parasite.

    Answer

    (a).

  5. Q5 · 2 marks · Short answerBoard level

    State two differences between Porifera and Cnidaria. [2]

    Hint

    Pores/tentacles.

    Answer

    Porifera have pores and a skeleton of spicules and are fixed; Cnidaria have tentacles with stinging cells and many can move.

  6. Q6 · 3 marks · Short answerHarder board level

    Why can the body of an annelid bend and move in a wave while a roundworm only thrashes? Link segmentation to movement. [3]

    Hint

    Rings.

    Answer

    Segmentation and a true body cavity let each ring contract independently with muscles and bristles, giving controlled crawling; roundworms lack segments and bend from side to side only.

  7. Q7 · 2 marks · Very short answerHarder board level

    A filarial worm is found in the lymph vessels of a patient. Name its phylum and state one feature. [2]

    Hint

    Round worm.

    Answer

    Nematoda; it is a round, unsegmented worm.

  8. Q8 · 3 marks · Short answerHarder board level

    Compare bilateral symmetry in flatworms with radial symmetry in echinoderms and name a practical advantage of each. [3]

    Hint

    Direction.

    Answer

    Bilateral animals have two similar halves and move head first; radial animals have parts around a centre and can respond from any direction.

  9. Q9 · 3 marks · Case-basedHOTS / competency

    Case. Fishermen find a blob with no head, no bones, a bell shape and tentacles that sting. (i) Name the phylum. [1] (ii) State two characters. [2]

    Hint

    Floating.

    Answer

    (i) Cnidaria. (ii) Radial symmetry and stinging cells on tentacles.

  10. Q10 · 4 marks · Case-basedHOTS / competency

    Case. A scientist finds an animal with no backbone, five arms, spiny skin and tube feet. (i) Name the animal and phylum. [2] (ii) Why can it not be an annelid? [2]

    Hint

    Echino-.

    Answer

    (i) Starfish; Echinodermata. (ii) It has no segmentation or bristles and shows radial symmetry.

Test your recall

Answer in your head or on paper first, then open the card. Pulling an answer out of memory makes it stick far better than re-reading.

  1. 1.Largest phylum?Show answer

    Arthropoda.

  2. 2.Example of segmented worm?Show answer

    Earthworm.

  3. 3.Pore-bearing phylum?Show answer

    Porifera.

  4. 4.Exoskeleton material in arthropods?Show answer

    Chitin.

  5. 5.Phylum of starfish?Show answer

    Echinodermata.

Non-Chordate Phyla: Porifera to Echinodermata: frequently asked questions

Is a jellyfish a fish?

No, it is a cnidarian.

Are earthworms parasites?

No, they are free-living.

What is a notochord?

A flexible rod along the back of chordate embryos.