Which of the following structural features is unique to echinoderms?
Answer: B
Echinoderms exhibit radial symmetry as adults and possess a unique water vascular system (hydrostatic skeleton) used for locomotion and feeding.
Q.22Medium
A researcher observes an organism with a notochord, pharyngeal slits, and a dorsal hollow nerve cord at some stage of development. To which phylum must this organism belong?
Answer: B
The presence of a notochord, pharyngeal slits, and dorsal hollow nerve cord are defining characteristics of the phylum Chordata, even if these features are present only during embryonic stages.
Q.23Medium
Which statement about the coelom is correct?
Answer: B
A coelom is a true body cavity completely lined by mesoderm-derived tissue (peritoneum). Coelomate organisms include annelids, molluscs, arthropods, echinoderms, and chordates.
Q.24Medium
What is the primary advantage of having a complete digestive system (with both mouth and anus) over an incomplete digestive system?
Answer: A
A complete digestive system allows specialized regions for ingestion, digestion, and egestion, enabling continuous feeding while previous meals are still being digested. This is more efficient than an incomplete system.
Q.25Medium
In the classification of animals, which of the following criteria is primarily used to place an organism in the phylum Annelida?
Answer: B
Annelids are characterized by true segmentation (metameric segmentation) with coelomic cavities in each segment. This distinguishes them from other invertebrates.
Advertisement
Q.26Medium
Birds possess air sacs in their respiratory system. What is the functional significance of this adaptation?
Answer: B
Air sacs create a unidirectional flow of air through the lungs, making gas exchange more efficient than in mammals. This adaptation is crucial for the high metabolic demands of flight.
Q.27Medium
Among the following, which organism is an example of a deuterostome?
Answer: B
Starfish belong to Echinodermata, a deuterostome phylum where the blastopore forms the anus. Earthworms, octopuses, and grasshoppers are protostomes where the blastopore forms the mouth.
Q.28Medium
What is the significance of the presence of a notochord in chordates?
Answer: B
The notochord is a flexible rod that provides skeletal support. In vertebrates, it is largely replaced by the vertebral column during development, though remnants persist as the nucleus pulposus of intervertebral discs.
Q.29Medium
A zoologist discovers a new organism with the following characteristics: segmented body, jointed appendages, exoskeleton, and open circulatory system. To which phylum should this organism be classified?
Answer: B
The combination of jointed appendages, chitinous exoskeleton, segmented body, and open circulatory system are characteristic features of phylum Arthropoda.
Q.30Medium
Which of the following correctly describes the relationship between symmetry and lifestyle in animals?
Answer: C
Bilateral symmetry with cephalization (concentration of sensory organs at the anterior end) is associated with active, directional movement. Radial symmetry is typical of sessile or slow-moving organisms.
Q.31Medium
Among molluscs, the development of a mantle and shell is primarily an adaptation for which function?
Answer: B
The mantle in molluscs secretes the shell, which provides protection for internal organs and serves as an attachment point for muscles. This is fundamental to molluscan body organization.
Q.32Medium
Segmentation is a key characteristic that distinguishes Annelida from which other phyla?
Answer: B
While Annelida and Arthropoda both show segmentation, Mollusca lacks true segmentation. Echinodermata and Chordata also lack typical segmentation seen in Annelida.
Q.33Medium
A student observes an organism with radial symmetry, stinging cells (cnidocytes), and a gastrovascular cavity. It belongs to which phylum?
Answer: B
The presence of cnidocytes (stinging cells), radial symmetry, and gastrovascular cavity are defining characteristics of Cnidaria (corals, jellyfish, hydra).
Q.34Medium
Which of the following amphibians shows neoteny in its life cycle?
Answer: B
Axolotl (a salamander) exhibits neoteny, retaining larval characteristics (external gills) throughout its life even after sexual maturity.
Q.35Medium
In the evolutionary progression of vertebrates, which feature first appeared in fish and was retained in all subsequent vertebrate groups?
Answer: B
The notochord and dorsal neural tube are fundamental chordate features appearing first in fish and retained throughout vertebrate evolution.
Q.36Medium
Which reptilian adaptation specifically reduces water loss while maintaining efficient gas exchange?
Answer: D
All three adaptations—keratinized skin, shelled eggs, and scales—collectively reduce water loss in reptiles while maintaining respiration and reproduction efficiency.
Q.37Medium
A marine organism displays a water vascular system and tube feet. Based on this, identify its phylum and larval symmetry type.
Answer: C
The water vascular system and tube feet are unique to Echinodermata. Despite radial adult symmetry, echinoderms have bilateral larvae, indicating deuterostome origin.
Q.38Medium
A researcher discovers that an organism lacks a true body cavity but possesses bilateral symmetry and specialized organ systems. Which phylum does it likely belong to?
Answer: B
Platyhelminthes (flatworms) are acoelomate with bilateral symmetry and organ systems. Cnidaria lacks bilateral symmetry; Nematoda has pseudocoel; Annelida has true coelom.
Q.39Medium
The presence of a pseudocoelom distinguishes which phylum from true coelomate animals?
Answer: B
Nematodes (roundworms) possess a pseudocoelom, a body cavity incompletely lined by mesoderm, distinguishing them from both acoelomates (Platyhelminthes) and eucoelomates (Annelida, Mollusca).
Q.40Medium
Among vertebrate classes, which one shows the transition from aquatic to terrestrial life with specific embryonic membranes?
Answer: B
Reptilia (and subsequent classes) show the complete adaptation to terrestrial life with amnion, chorion, and allantois. Amphibia still requires water for reproduction.
