In comparative anatomy, the presence of homologous structures in different vertebrate classes primarily indicates:
Answer: B
Homologous structures (like limbs in vertebrates) indicate common ancestry and evolutionary relationships, supporting the concept of descent with modification.
Q.42Medium
The notochord in vertebrates is embryologically derived from which germ layer?
Answer: D
The notochord develops from the chordamesoderm (primitive pit), which gives rise to axial structures in chordates.
Q.43Medium
The water vascular system is unique to which phylum and plays what primary role?
Answer: A
Echinoderms possess a unique water vascular system derived from the coelom, used for locomotion, feeding, and respiration through tube feet.
Q.44Medium
In arthropods, the tracheal system for respiration is most extensively developed in which group?
Answer: A
Insects have highly developed tracheal systems with extensive branching allowing efficient terrestrial respiration, unlike crustaceans which use gills.
Q.45Medium
Which characteristic is unique to members of Class Amphibia among vertebrates?
Answer: B
Amphibians uniquely have a biphasic life cycle, spending early life in water as aquatic larvae and later life on land as terrestrial adults, undergoing metamorphosis.
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Q.46Medium
The presence of pharyngeal slits in chordates serves which primary function in adults?
Answer: B
Pharyngeal slits function in respiration (aquatic chordates) and are modified into the middle ear structure and eustachian tube in terrestrial vertebrates.
Q.47Medium
Which adaptation allows marine fish to maintain osmoregulation in hyperosmotic environments?
Answer: B
Marine fish conserve water by producing concentrated urine and actively excrete excess salts through specialized gill cells, maintaining internal osmotic balance.
Q.48Medium
Which of the following statements about mammalian hair and reptilian scales is correct?
Answer: B
Both hair and scales are epidermal structures but serve different functions: hair insulates in mammals while scales provide waterproofing in reptiles.
Q.49Medium
Which feature of flatworms (Platyhelminthes) represents a primitive characteristic compared to higher animals?
Answer: B
The incomplete digestive system with a single opening (gastrovascular cavity) in flatworms is primitive compared to higher animals with complete digestive tracts.
Q.50Medium
In the context of animal classification, which of the following pairs represents organisms from the same phylum but different classes?
Answer: C
Frogs belong to Class Amphibia while snakes belong to Class Reptilia, both are in Phylum Chordata; all other pairs are from different phyla.
Q.51Medium
Which characteristic of sponges (Porifera) indicates they are among the most primitive animals despite their complex structure?
Answer: A
Sponges lack true tissues (being cellular level organization) and have no nervous, digestive, or circulatory systems, indicating primitive evolutionary status.
Q.52Medium
A marine organism exhibits radial symmetry, possesses nematocysts, and has a gastrovascular cavity. During its life cycle, it alternates between a sessile polyp form and a free-swimming medusa form. Which phylum does this organism belong to, and what is the ecological significance of this alternation?
Answer: A
This describes the metagenesis (alternation of generations) in Cnidarians. The polyp form is sessile and primarily filter-feeds, while the medusa is motile and actively hunts. Nematocysts and gastrovascular cavity are defining features of Cnidaria. This lifecycle strategy allows the species to exploit different ecological niches and resources.
Q.53Medium
A patient has difficulty in accommodation of the eye. Which lens condition is responsible?
Answer: A
Presbyopia occurs due to loss of lens elasticity with age, reducing accommodation ability for near vision.
Q.54Medium
Which of the following hormones is NOT produced by the anterior pituitary?
Answer: C
ADH (Antidiuretic hormone) is produced by the hypothalamus and stored/released by the posterior pituitary, not the anterior pituitary.
Q.55Medium
The normal pH of blood is maintained primarily by:
Answer: D
Blood pH (7.35-7.45) is maintained by multiple buffer systems including bicarbonate, phosphate, and protein buffers working together.
Q.56Medium
In the small intestine, the majority of nutrient absorption occurs in the:
Answer: B
The jejunum is the primary site for nutrient absorption due to its extensive villi and optimal length for absorption process.
Q.57Medium
Which blood cells are responsible for producing antibodies?
Answer: B
Plasma cells (differentiated B lymphocytes) produce and secrete specific antibodies in response to antigens.
Q.58Medium
The resting membrane potential of a typical neuron is approximately:
Answer: B
The resting potential is maintained at -70 mV primarily by the Na+/K+ ATPase pump and differential ion permeability.
Q.59Medium
A person experiences vasoconstriction and increased heart rate upon seeing a predator. This response is mediated by:
Answer: B
The fight-or-flight response involves sympathetic activation releasing epinephrine and norepinephrine causing vasoconstriction and tachycardia.
Q.60Medium
Which of the following conditions results from deficiency of intrinsic factor?
Answer: B
Intrinsic factor is required for B12 absorption; its deficiency leads to pernicious anemia due to impaired vitamin B12 absorption.
