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Animal Kingdom
Biology · Class 11NCERT pp. 37–512 sets × 25 questions
Key facts and formulas for Animal Kingdom, three worked sample questions, and two full practice sets. Every question has a hint, a reason for every option and a step-by-step solution, with a calculator or animation where one helps. English and Hinglish.
Key facts for this chapter
| Idea | Rule or fact |
|---|
| Symmetry and germ layers | Sponges asymmetric; coelenterates and ctenophores radial and diploblastic; flatworms onward bilateral and triploblastic. Echinoderm adults radial, larvae bilateral. |
| Coelom types | Acoelomate: flatworms. Pseudocoelomate: aschelminthes. Coelomate: annelids onward. Enterocoelous: echinoderms, hemichordates, chordates. |
| Segmentation | Only Annelida, Arthropoda and Chordata are segmented; molluscs and echinoderms are not. |
| Circulation | Annelids closed; arthropods and most molluscs open; Octopus (cephalopod) closed. |
| Heart chambers | Fish 2, amphibians 3, most reptiles 3, birds and mammals 4. |
| Excretion | Ammonotelic: bony fish, tadpoles. Ureotelic: mammals, adult frogs. Uricotelic: birds, reptiles. |
| Chordate groups | Urochordata: Ascidia; Cephalochordata: Branchiostoma; Cyclostomata: Petromyzon; Hemichordata is non-chordate (stomochord). |
| Fishes | Chondrichthyes: placoid scales, heterocercal tail, Scoliodon. Osteichthyes: bony, Hippocampus, Labeo. Latimeria is a living fossil. |
| Larvae and links | Tornaria-Balanoglossus, bipinnaria-Asterias, ammocoete-Petromyzon. Peripatus, Neopilina, Archaeopteryx, platypus are links. |
| Mammals and birds | Mammals have 7 cervical vertebrae and RBCs without nucleus; platypus and echidna lay eggs. Birds have a syrinx, crop, gizzard and pneumatic bones. |
Three sample questions
Q1. Which phylum has radially symmetrical adults but bilaterally symmetrical larvae?
- Coelenterata
- Echinodermata
- Ctenophora
- Platyhelminthes
Hint and solution
Hint: Think of a star fish: the adult looks like a star, but its swimming larva has a left and right side.
- Adult radial + larva bilateral — We need a phylum whose symmetry changes from larva to adult.
- Coelenterata, Ctenophora: radial throughout — These two groups stay radial or biradial in all stages, so they are out.
- Platyhelminthes: bilateral throughout — Flatworms are bilateral as adults too, so they do not fit.
- Echinodermata: adult radial, larva bilateral — Echinoderms show exactly this change. So the answer is Echinodermata. Option B.
Answer: B. Echinoderm adults are radial and their larvae are bilateral. Coelenterates and ctenophores are radial throughout and flatworms are bilateral.
Q2. Consider: (i) Coelenterates are diploblastic. (ii) Mesoglea is a third germ layer. (iii) Platyhelminthes are triploblastic. Which are correct?
- (i) and (iii) only
- (i) and (ii) only
- (ii) and (iii) only
- (i), (ii) and (iii)
Hint and solution
Hint: Check each statement separately. Ask whether mesoglea has cells arranged as a true layer.
- Diploblastic = ectoderm + endoderm only — Coelenterates have two germ layers, so statement (i) is true.
- Mesoglea: undifferentiated, not a germ layer — The mesoglea sits between the two layers but is not formed as a third germ layer. So (ii) is false.
- Platyhelminthes: ectoderm, mesoderm, endoderm — Flatworms are triploblastic, so statement (iii) is true.
- True: (i) and (iii) — Only (i) and (iii) are correct. Option A.
Answer: A. Mesoglea is undifferentiated and is not a germ layer, so statement (ii) is wrong.
Q3. Match Column I with Column II.
a. Cnidoblasts i. Platyhelminthes
b. Comb plates ii. Mollusca
c. Flame cells iii. Coelenterata
d. Radula iv. Ctenophora
- a-iv, b-iii, c-i, d-ii
- a-iii, b-iv, c-ii, d-i
- a-i, b-ii, c-iii, d-iv
- a-iii, b-iv, c-i, d-ii
Hint and solution
Hint: Cnidoblasts are stinging cells, comb plates give the name comb jellies, flame cells excrete in flatworms, and the radula is a rasping tongue.
- Cnidoblasts → Coelenterata — Stinging cells (cnidoblasts) are the hallmark of coelenterates, so a matches iii.
- Comb plates → Ctenophora — Eight rows of ciliated comb plates give comb jellies their name, so b matches iv.
- Flame cells → Platyhelminthes; radula → Mollusca — Flame cells do osmoregulation and excretion in flatworms, and the radula is the rasping organ of molluscs. So c-i and d-ii.
- a-iii, b-iv, c-i, d-ii — This set is in the last option. Option D.
Answer: D. Cnidoblasts belong to coelenterates, comb plates to ctenophores, flame cells to flatworms and the radula to molluscs.
How to use this chapter
Read the NCERT pages first, then attempt Set 1 without the hints. Note every wrong answer in a mistake list, read the reason for each option, and retry Set 2 two days later. A topic is solid when you can say why each wrong option is wrong.