Platyhelminthes, Nemathelminthes and Annelida Practice Questions
40 free Platyhelminthes, Nemathelminthes and Annelida practice questions for the Zoology. Tap an option to answer — you get instant feedback, the correct answer, and a detailed explanation for every question.
Which specialized excretory cells are characteristic of Phylum Platyhelminthes and function primarily in osmoregulation?
- A Nephridia (annelid-type)
- B Flame cells (Protonephridia)
- C Malpighian tubules (insect-type)
- D Green glands (crustacean-type)
Correct answer: Flame cells (Protonephridia)
Flame cells are the functional units of the protonephridial system in flatworms (Platyhelminthes). A tuft of cilia flickers like a flame, drawing interstitial fluid into the tubule system to regulate water and ion balance (osmoregulation).
Annelids are characterized by 'metamerism.' What does this term refer to?
- A The ability to change color for camouflage
- B The presence of a false body cavity
- C Repetition of similar body segments
- D A life cycle involving two distinct hosts
Correct answer: Repetition of similar body segments
Metamerism is the true segmentation found in Annelida, where the body is divided into a series of similar units called metameres. Each segment often contains its own sets of circulatory, nervous, and excretory organs, allowing for functional specialization.
Which type of body cavity is found in Nemathelminthes (Nematodes)?
- A Acoelomate (no body cavity)
- B Pseudocoelomate (false coelom)
- C Eucoelomate (true coelom)
- D Haemocoel (open blood cavity)
Correct answer: Pseudocoelomate (false coelom)
Nematodes possess a pseudocoelom — a fluid-filled body cavity not completely lined by mesoderm. This cavity acts as a hydrostatic skeleton and facilitates the transport of nutrients and waste products.
In the Annelid Hirudo medicinalis (Leech), how is the coelom modified?
- A It is completely absent (acoelomate)
- B It is replaced by a water-vascular system
- C It is packed with botryoidal tissue
- D It remains as a large fluid-filled space
Correct answer: It is packed with botryoidal tissue
In leeches (Hirudo medicinalis), the coelom is greatly reduced by connective tissue and muscle. The remaining spaces are filled with botryoidal tissue, which is involved in excretion and storage of nutrients.
Flatworms are described as 'acoelomate' because:
- A They lack a digestive tract entirely
- B They have a cavity lined by endoderm
- C Parenchyma tissue fills the body wall space
- D They possess a cavity derived from the blastocoel
Correct answer: Parenchyma tissue fills the body wall space
Platyhelminthes (flatworms) are acoelomate — they lack a true body cavity. The region between the outer epidermis and inner gut lining is packed with solid mesodermal parenchyma tissue, leaving no open fluid-filled space.
Which of the following describes the nervous system structure in most Annelids?
- A A simple diffuse nerve net scattered throughout the body with no centralised ganglia
- B A dorsal brain with a ventral nerve cord and segmental ganglia
- C A single hollow dorsal nerve cord running the full length of the body
- D A nerve ring encircling the digestive tract near the posterior end
Correct answer: A dorsal brain with a ventral nerve cord and segmental ganglia
Annelids typically have a pair of cerebral ganglia (brain) and a double ventral nerve cord. This cord runs the length of the body with local swellings or ganglia in each segment to coordinate movement.
Nematodes are known for 'eutely.' What does this biological phenomenon imply?
- A The capacity to regenerate lost body segments or appendages after injury
- B A constant number of cells in all adult individuals of a species
- C The simultaneous presence of both male and female reproductive organs in one individual
- D A one-way digestive system in which food enters and wastes exit through the same opening
Correct answer: A constant number of cells in all adult individuals of a species
Eutely is a condition where the number of cells in the adult body is fixed and constant for a species (e.g., C. elegans). Growth occurs through cell enlargement rather than cell division after embryonic development.
The 'Chloragogen cells' found in the earthworm are functionally analogous to which vertebrate organ?
- A Kidney — filters nitrogenous waste from the blood
- B Heart — circulates blood around the body
- C Liver — intermediary metabolism and detoxification
- D Lung — primary organ of gas exchange and respiration
Correct answer: Liver — intermediary metabolism and detoxification
Chloragogen cells surround the intestine and carry out intermediary metabolism, glycogen synthesis, and protein deamination — functions closely analogous to those of the vertebrate liver.
What is the function of the 'Typhlosole' in the intestine of an earthworm?
- A To secrete digestive enzymes that chemically break down incoming food particles
- B To increase the surface area for nutrient absorption
- C To store undigested food material before it passes to the rectum
- D To drive blood circulation into the surrounding intestinal wall capillaries
Correct answer: To increase the surface area for nutrient absorption
The typhlosole is a dorsal longitudinal fold of the intestinal wall. By protruding into the lumen, it increases the internal surface area, making the absorption of digested nutrients more efficient.
In Phylum Nematoda, which of the following is ABSENT in their anatomical structure?
- A Longitudinal muscles
- B Complete digestive tract
- C Circular muscles
- D Cuticle
Correct answer: Circular muscles
Nematodes possess longitudinal muscles but lack circular muscles in their body wall. This absence results in their characteristic whip-like, thrashing movement rather than peristaltic motion.
Which parasite belongs to Platyhelminthes and requires a snail as an intermediate host in its life cycle?
- A Ascaris lumbricoides
- B Ancylostoma duodenale
- C Fasciola hepatica (Liver Fluke)
- D Wuchereria bancrofti
Correct answer: Fasciola hepatica (Liver Fluke)
Fasciola hepatica (Liver Fluke) is a trematode flatworm. Its complex life cycle involves sexual reproduction in a vertebrate host and asexual stages in a molluscan intermediate host (snail).
Annelids utilize which respiratory pigment, often dissolved in the plasma rather than inside red blood cells?
- A Hemoglobin
- B Hemocyanin
- C Hemerythrin
- D Cytochrome
Correct answer: Hemoglobin
Many annelids, like earthworms, use hemoglobin (or erythrocruorin) to transport oxygen. Unlike vertebrates, this pigment is usually dissolved directly in the blood plasma.
The 'Parapodia' found in Polychaetes (e.g., Nereis) serve which two primary functions?
- A Scolex and Proglottids
- B Rostellum and Setae (bristles)
- C Cercus and Body Segments
- D Caput and Metameres (somites)
Correct answer: Scolex and Proglottids
The scolex is the anterior attachment organ equipped with hooks or suckers. The rest of the body consists of a chain of reproductive units called proglottids.
The body of a tapeworm (Cestoda) consists of a head and a series of segments. These are scientifically termed:
- A Parenchyma filling intercellular spaces
- B A non-extensible cuticle
- C A mineralised calcified outer shell
- D Rigid segmental septa dividing the body
Correct answer: A non-extensible cuticle
Nematodes have a tough, collagenous cuticle that is under high hydrostatic pressure from the pseudocoelomic fluid. This creates a hydrostatic skeleton that allows longitudinal muscles to produce sinusoidal movement.
Nematodes move in a 'thrashing' motion because their high-pressure fluid-filled cavity acts against which structure?
- A Parenchyma
- B A non-extensible cuticle
- C A calcified shell
- D Segmented septa
Correct answer: A non-extensible cuticle
Nematodes have a tough, collagenous cuticle that is under high hydrostatic pressure from the pseudocoelomic fluid. This creates a hydrostatic skeleton that allows longitudinal muscles to produce sinusoidal movement.
Which structure in the Annelid Pheretima (Earthworm) is responsible for the secretion of the cocoon during reproduction?
- A Prostomium
- B Clitellum
- C Setae
- D Spermatheca
Correct answer: Clitellum
The clitellum is a glandular thickening of the body wall (segments 14-16 in earthworms). It secretes a mucous cocoon where fertilization and embryonic development take place.
Ascaris lumbricoides shows sexual dimorphism. Which of the following is a characteristic of the male worm?
- A Larger body size relative to the female
- B A straight, non-curved posterior end
- C A curved posterior end with penial spicules
- D Presence of a clitellum for cocoon secretion
Correct answer: A curved posterior end with penial spicules
Male Ascaris are smaller than females and have a distinctively curved tail. They also possess cloacal spicules (penial setae) used to open the female's vulva during copulation.
Which of the following is a 'free-living' Platyhelminth?
- A Taenia solium
- B Schistosoma mansoni
- C Dugesia (Planaria)
- D Echinococcus granulosus
Correct answer: Dugesia (Planaria)
Planaria are members of the class Turbellaria, which are predominantly non-parasitic and free-living in aquatic environments. Most other flatworm classes (Trematoda, Cestoda) are strictly parasitic.
In Annelids, the excretory organs that open at both ends (one into the coelom and one to the exterior) are called:
- A Protonephridia
- B Metanephridia
- C Coxal glands
- D Renette cells
Correct answer: Metanephridia
Metanephridia begin with a ciliated funnel called a nephrostome that collects coelomic fluid. The fluid is processed in a tubule and excreted through a nephridiopore.
What is the primary mode of infection for the 'Hookworm' (Ancylostoma duodenale)?
- A Ingestion of undercooked pork containing encysted larvae
- B Bite of an infected female Anopheles mosquito carrying infective larvae
- C Active penetration of the skin by filariform larvae
- D Drinking water contaminated with embryonated eggs passed in faeces
Correct answer: Active penetration of the skin by filariform larvae
Hookworm larvae live in the soil and infect humans by burrowing directly through the skin, usually of the feet. They then travel through the bloodstream to the lungs and eventually the small intestine.
Which type of body cavity is present in Platyhelminthes?
- A Coelomate
- B Pseudocoelomate
- C Acoelomate
- D Hemocoel
Correct answer: Acoelomate
Platyhelminthes are acoelomate, meaning they lack a true body cavity. The space between organs is filled with mesenchyme tissue.
Which excretory structures are found in flatworms?
- A Nephridia
- B Malpighian tubules
- C Flame cells
- D Green glands
Correct answer: Flame cells
Flame cells are specialized excretory structures in Platyhelminthes. They help in osmoregulation and waste removal.
Which of the following is a free-living flatworm?
- A Taenia
- B Fasciola
- C Planaria
- D Schistosoma
Correct answer: Planaria
Planaria is a free-living flatworm found in freshwater habitats. Most other flatworms are parasitic.
What type of digestive system is found in Platyhelminthes?
- A Complete
- B Incomplete
- C Mostly absent
- D Dual
Correct answer: Incomplete
Platyhelminthes have an incomplete digestive system with a single opening. Some parasitic forms like tapeworms lack a digestive system entirely.
Which body symmetry is shown by Platyhelminthes, Nemathelminthes, and Annelida?
- A Radial symmetry
- B Bilateral symmetry
- C Asymmetry
- D Spherical symmetry
Correct answer: Bilateral symmetry
All three phyla exhibit bilateral symmetry. This allows for a distinct head and tail region.
Which type of body cavity is found in Nemathelminthes?
- A True coelom
- B Pseudocoelom
- C Acoelom
- D Open hemocoel
Correct answer: Pseudocoelom
Nemathelminthes are pseudocoelomates, meaning they have a body cavity not fully lined with mesoderm. It acts as a hydrostatic skeleton.
Which structure is absent in Nematodes?
- A Complete digestive system
- B Circulatory system
- C Muscular system
- D Central nervous system
Correct answer: Circulatory system
Nematodes lack a circulatory system. Nutrients are distributed through body fluid in the pseudocoel.
Which type of digestive system is found in Nematodes?
- A Incomplete
- B Absent
- C Complete
- D Dual
Correct answer: Complete
Nematodes have a complete digestive system with separate mouth and anus. This allows efficient digestion.
What is the mode of locomotion in Nematodes?
- A Ciliary movement
- B Muscular contraction
- C Thrashing movement
- D Gliding
Correct answer: Thrashing movement
Nematodes move in a thrashing motion due to longitudinal muscles and high internal pressure. They lack circular muscles.
Which nematode is a human intestinal parasite?
- A Nereis
- B Ascaris
- C Hirudo
- D Planaria
Correct answer: Ascaris
Ascaris lumbricoides is a common intestinal parasite in humans. It infects through contaminated food or water.
Which phylum shows true segmentation or metamerism?
- A Platyhelminthes
- B Nemathelminthes
- C Annelida
- D Cnidaria
Correct answer: Annelida
Annelids exhibit true metamerism, where the body is divided into repeated segments. This improves movement and organ specialization.
Which excretory organs are present in annelids?
- A Flame cells
- B Green glands
- C Malpighian tubules
- D Paired nephridia
Correct answer: Paired nephridia
Annelids possess nephridia for excretion and osmoregulation. They are similar to kidneys in function.
Which respiratory pigment is found in many annelids?
- A Hemoglobin
- B Hemocyanin
- C Myoglobin
- D Carotene
Correct answer: Hemoglobin
Many annelids use hemoglobin dissolved in plasma for oxygen transport. It aids in efficient respiration.
Which structure increases the absorptive surface in the intestine of earthworms?
- A Typhlosole
- B Nephridia
- C Parapodia
- D Bristle-like setae
Correct answer: Typhlosole
The typhlosole is an internal fold in the intestine of earthworms. It increases the surface area for absorption.
Which function is performed by parapodia in polychaetes?
- A Digestion and absorption
- B Excretion and osmoregulation
- C Reproduction and mating
- D Locomotion and respiration
Correct answer: Locomotion and respiration
Parapodia are lateral appendages used for movement and gas exchange. They are well-developed in polychaetes like Nereis.
Which structure secretes the cocoon in earthworms?
- A Clitellum
- B Nephridia
- C Setae
- D Parapodia
Correct answer: Clitellum
The clitellum secretes a cocoon during reproduction. It plays a key role in the development of embryos.
Which class of Platyhelminthes includes tapeworms?
- A Turbellaria
- B Trematoda
- C Monogenea
- D Cestoda
Correct answer: Cestoda
Cestoda includes parasitic tapeworms. They lack a digestive system and absorb nutrients from the host.
Which annelid has a modified coelom forming sinuses?
- A Nereis
- B Earthworm
- C Planaria
- D Leeches
Correct answer: Leeches
In leeches, the coelom is reduced and modified into sinuses. This aids in circulation and movement.
Which of the following is a parasitic flatworm requiring an intermediate host?
- A Fasciola
- B Planaria
- C Nereis
- D Earthworm
Correct answer: Fasciola
Fasciola (liver fluke) is a parasitic flatworm. It requires a snail as an intermediate host for its life cycle.
What does eutely in nematodes indicate?
- A Fixed number of cells
- B Variable number of cells
- C Rapid cell division
- D Large body size
Correct answer: Fixed number of cells
Eutely means a fixed number of cells in the organism. Growth occurs by cell enlargement rather than cell division.