Animal Kingdom — Class 11 Biology NCERT Solutions (Free)
Free step-by-step NCERT solutions for Class 11 Biology chapter "Animal Kingdom" — 8 important questions with detailed answers for CBSE board exam preparation.
TL;DR: Free step-by-step NCERT solutions for Class 11 Biology chapter "Animal Kingdom" — 8 important questions with detailed answers for CBSE board exam prep…
Written & reviewed by the Syllab.in Academic Team (CBSE/NCERT subject experts) · Updated
NCERT Solutions for Class 11 Biology — Animal Kingdom. Step-by-step answers to all 8 textbook questions from this chapter, written for CBSE board preparation and free to use.
Animal Kingdom — All 8 Questions Solved
Q1. Define phylum Porifera and name two characteristics.
Porifera are the simplest multicellular animals, commonly called sponges. Two key characteristics are:
1. Presence of pores or ostia on the body surface through which water enters.
2. Absence of true tissues and organs; body composed of loosely organized cells.
Q2. What is a cnidocyte? Where is it found?
A cnidocyte is a specialized stinging cell found in organisms of phylum Cnidaria (e.g., jellyfish, sea anemones, corals). It contains a nematocyst, an organelle with a coiled thread-like structure that ejects a toxin when triggered, used for capturing prey and defense.
Q3. Distinguish between radial and bilateral symmetry with examples.
Radial symmetry: Body parts arranged around a central axis; organism can be divided into equal halves by any plane passing through the center. Example: Sea anemone, jellyfish.
Bilateral symmetry: Body has a distinct anterior (head) and posterior (tail) end; can be divided into identical left and right halves by only one plane. Example: Fish, earthworm, human.
Q4. What are the main features of phylum Platyhelminthes?
Main features of Platyhelminthes (flatworms):
1. Bilateral symmetry and presence of three germ layers (triploblastic).
2. Absence of body cavity (acoelomate).
3. Simple nervous system with a brain-like structure.
4. Many are parasitic; some are free-living.
5. Gas exchange occurs by diffusion across body wall.
Examples: Planaria (free-living), Taenia, Fasciola (parasitic).
Q5. Describe the structure and function of nephridia in earthworms.
Nephridia are excretory organs in earthworms (segmented worms). Structure: Each segment typically contains a pair of nephridia, consisting of a funnel-like nephrostome opening into the coelom, a coiled tubule, and a nephridiopore opening to the exterior.
Function: Nephridia collect metabolic wastes from the coelom and blood, and discharge them as urine through the nephridiopore, maintaining osmoregulation.
Q6. What is a notochord? Why is it significant in classification?
A notochord is a flexible rod of cartilaginous tissue running along the dorsal side of the body during embryonic development in chordates. It provides structural support.
Significance: It is a key characteristic that defines the phylum Chordata. In most vertebrates, the notochord is replaced by the vertebral column during development, but its presence in embryos confirms chordate ancestry and is used to classify organisms as chordates.
Q7. Compare external gills in tadpoles with lungs in adult frogs (5-mark answer).
External gills in tadpoles (larval stage):
1. Filamentous structures protruding from the sides of the head.
2. Large surface area for gas exchange in aquatic environment.
3. Directly exposed to water; oxygen dissolved in water diffuses across gill surface.
4. Short lifespan, replaced by internal gills then lungs as tadpole develops.
Lungs in adult frogs (metamorphosed adults):
1. Internal sac-like structures located in thoracic cavity.
2. Reduced surface area compared to gills; supplemented by skin respiration.
3. Gas exchange with air in terrestrial/semi-aquatic environment.
4. Permanent; enable frog to breathe on land.
Significance: This transition from aquatic gill respiration to terrestrial lung respiration reflects adaptation to changing environmental demands during metamorphosis.
Q8. Name the three layers of cells in a sponge and describe their roles.
Three cell layers in a sponge:
1. Pinacocytes (external layer): Flat cells forming the outer epithelial layer; protect the sponge and regulate water flow through ostia.
2. Choanocytes (internal layer): Flagellated cells lining the internal cavity (spongocoel); their beating flagella create water currents and trap food particles for ingestion.
3. Amoebocytes (middle region): Amoeba-like cells in the mesoglea; perform nutrient distribution, waste transport, and can develop into reproductive cells or other cell types.
Animal Kingdom — Practice MCQs with Answers
Attempt these 20 multiple-choice questions after working through the solutions above. Each carries the correct option and the reasoning behind it, so a wrong answer tells you which idea to revisit.
MCQ 1. Which of the following phyla is characterized by the absence of a true coelom?
- A. Annelida
- B. Arthropoda
- C. Platyhelminthes
- D. Mollusca
Answer: C. Platyhelminthes — Platyhelminthes are acoelomates, meaning they do not possess a fluid-filled body cavity (coelom) between the body wall and the gut. Annelids, arthropods, and molluscs are coelomates.
MCQ 2. In sponges, the central cavity through which water circulates before exiting is known as the:
- A. Choanocyte
- B. Osculum
- C. Spongocoel
- D. Ostia
Answer: C. Spongocoel — The spongocoel is the large central cavity in sponges. Water enters through numerous small pores (ostia) and exits through a larger opening (osculum), while choanocytes line the spongocoel and canals.
MCQ 3. The characteristic stinging cells, cnidoblasts or nematocysts, are found in which phylum?
- A. Porifera
- B. Cnidaria
- C. Ctenophora
- D. Platyhelminthes
Answer: B. Cnidaria — Cnidoblasts (or cnidocytes) containing nematocysts are specialized stinging cells unique to the phylum Cnidaria, used for anchorage, defense, and capture of prey.
MCQ 4. Flame cells are specialized structures for excretion and osmoregulation in which group of animals?
- A. Annelida
- B. Platyhelminthes
- C. Aschelminthes
- D. Cnidaria
Answer: B. Platyhelminthes — Flame cells (protonephridia) are excretory structures found in platyhelminthes like Planaria and Fasciola, responsible for removing waste products and regulating water balance.
MCQ 5. Animals belonging to the phylum Aschelminthes are characterized by possessing a:
- A. True coelom
- B. Pseudocoelom
- C. Acoelom
- D. Haemocoel
Answer: B. Pseudocoelom — Aschelminthes are pseudocoelomates, meaning they have a body cavity that is not lined by mesoderm, unlike a true coelom which is completely lined by mesoderm.
MCQ 6. Metameric segmentation is a distinct feature of the body plan in which of the following phyla?
- A. Platyhelminthes
- B. Aschelminthes
- C. Annelida
- D. Mollusca
Answer: C. Annelida — Metameric segmentation, where the body is externally and internally divided into a series of similar segments, is a characteristic feature observed in the phylum Annelida.
MCQ 7. The exoskeleton of arthropods is primarily composed of which complex carbohydrate?
- A. Cellulose
- B. Starch
- C. Chitin
- D. Glycogen
Answer: C. Chitin — The hard, protective exoskeleton of arthropods is made of chitin, a complex polysaccharide that provides structural support and protection.
MCQ 8. Which of the following phyla represents eucoelomates derived from enterocoelous development?
- A. Annelida
- B. Arthropoda
- C. Mollusca
- D. Echinodermata
Answer: D. Echinodermata — Echinodermata, along with Hemichordata and Chordata, are deuterostomes that typically exhibit enterocoelous coelom formation, where the coelom arises from pouches of the embryonic gut. Annelids, arthropods, and molluscs are protostomes with schizocoelous coelom formation.
MCQ 9. Beyond locomotion, which of the following is an additional crucial function facilitated by the water vascular system in echinoderms?
- A. Digestion and nutrient absorption
- B. Gas exchange and waste removal
- C. Internal transport of hormones
- D. Protection from predators by secreting toxins
Answer: B. Gas exchange and waste removal — While primarily known for locomotion and food capture, the water vascular system in echinoderms also plays a significant role in gas exchange (respiration) and the removal of nitrogenous waste products through the thin walls of the tube feet.
MCQ 10. The notochord-like structure found in Hemichordates, which is a hollow outgrowth from the buccal cavity, is known as:
- A. Notochord
- B. Post-anal tail
- C. Stomochord
- D. Pharyngeal gill slits
Answer: C. Stomochord — Hemichordates possess a stomochord, which is a short, tubular, diverticulum of the buccal cavity. It was earlier considered a notochord but is now recognized as a separate structure.
MCQ 11. Which of the following is an essential characteristic that must be present at some stage of life in all chordates?
- A. Jaws
- B. Paired appendages
- C. Notochord
- D. Exoskeleton
Answer: C. Notochord — The presence of a notochord is one of the four fundamental characteristics (along with a dorsal hollow nerve cord, pharyngeal gill slits, and a post-anal tail) that define all chordates at some stage of their development.
MCQ 12. Cyclostomes are unique among vertebrates due to the absence of:
- A. Brain
- B. Gills
- C. Jaws
- D. Heart
Answer: C. Jaws — Cyclostomes, such as lampreys and hagfish, are the most primitive vertebrates characterized by a jawless mouth, making them distinct from other jawed vertebrates (Gnathostomata).
MCQ 13. In cartilaginous fishes (Chondrichthyes), the gill slits are:
- A. Covered by an operculum
- B. Six to seven pairs and covered
- C. Five to seven pairs and naked
- D. Present as a single pair
Answer: C. Five to seven pairs and naked — Chondrichthyes, like sharks and rays, have five to seven pairs of gill slits that are typically separate and not covered by an operculum, unlike bony fishes.
MCQ 14. Bony fishes (Osteichthyes) can be distinguished from cartilaginous fishes by the presence of:
- A. Placoid scales
- B. Pectoral fins
- C. Operculum
- D. Ventral mouth
Answer: C. Operculum — Osteichthyes, or bony fishes, possess an operculum (gill cover) that protects their four pairs of gills, which is absent in cartilaginous fishes.
MCQ 15. Which of the following statements is incorrect regarding circulatory systems in vertebrates?
- A. Fish have a two-chambered heart with single circulation.
- B. Amphibians and most reptiles have a three-chambered heart with incomplete double circulation.
- C. Crocodiles, birds, and mammals all possess a four-chambered heart.
- D. All reptiles have a three-chambered heart, regardless of species.
Answer: D. All reptiles have a three-chambered heart, regardless of species. — The statement 'All reptiles have a three-chambered heart, regardless of species' is incorrect. While most reptiles have a three-chambered heart, crocodiles are a notable exception, possessing a four-chambered heart.
MCQ 16. An adaptation for flight observed in birds (Aves) is the presence of:
- A. Dense bones
- B. Solid bones
- C. Pneumatic bones
- D. Cartilaginous bones
Answer: C. Pneumatic bones — Birds possess pneumatic bones, which are hollow and filled with air cavities. This structural adaptation significantly reduces their body weight, aiding in flight.
MCQ 17. Which of the following is a unique characteristic distinguishing all mammals from other vertebrates?
- A. Presence of hair
- B. Four-chambered heart
- C. Mammary glands
- D. External ears (pinnae)
Answer: C. Mammary glands — Mammary glands, which produce milk to nourish their young, are a defining and exclusive characteristic of all mammals.
MCQ 18. Which of the following phyla consists of diploblastic animals?
- A. Annelida
- B. Cnidaria
- C. Platyhelminthes
- D. Arthropoda
Answer: B. Cnidaria — Diploblastic animals, such as those in Phylum Cnidaria, develop from two embryonic germ layers: the ectoderm and endoderm, with an undifferentiated mesoglea in between.
MCQ 19. Radial symmetry is observed in adult forms of which of the following phyla, while their larval forms often exhibit bilateral symmetry?
- A. Cnidaria
- B. Ctenophora
- C. Echinodermata
- D. Porifera
Answer: C. Echinodermata — Echinoderms are unique in displaying radial symmetry as adults but possessing bilaterally symmetrical larval stages, suggesting an evolutionary link to bilaterally symmetrical ancestors.
MCQ 20. Identify the correct match between the phylum and its characteristic level of body organization.
- A. Porifera - Tissue level
- B. Cnidaria - Organ level
- C. Platyhelminthes - Organ-system level
- D. Aschelminthes - Organ-system level
Answer: D. Aschelminthes - Organ-system level — Aschelminthes (roundworms) typically exhibit the organ-system level of organization, where organs are associated to form functional systems. Porifera have cellular level, Cnidaria have tissue level, and Platyhelminthes have organ level.
How to Use These Solutions
Attempt each question yourself first and only then compare with the worked answer. Marks in the CBSE board exam are awarded for the METHOD as much as the final result, so reproduce the steps rather than memorising the last line. Where a solution states a law, a formula or a definition, learn that wording — examiners look for it.
Related practice for this chapter: chapter MCQs, previous-year questions, revision notes and sample papers.