Q21. Animals exhibiting repetitive body units, such as those found in annelids, demonstrate a body plan known as:
a) Metamerism
b) Symmetry
c) Notochord
d) Coelom
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Correct Answer: a) Metamerism
Explanation: Metamerism refers to segmentation along the body, with each segment possessing similar structures or organs. Earthworms clearly show this repetition of segments. Segmentation allows for specialization of body regions and increases movement efficiency.
Q22. Which of the following exhibits external metamerism?
a) Roundworms
b) Tapeworms
c) Earthworms
d) Jellyfish
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Correct Answer: c) Earthworms
Explanation: Earthworms (Annelida) exhibit prominent external segmentation. The body is divided into rings, visible on the outside, with each segment containing similar internal structures. This segmentation allows for more efficient movement and burrowing.
Q23: Segmentation plays a significant role in the evolution of:
a) Increased movement efficiency
b) Simple digestive systems
c) Diploblastic organization
d) Reduced organ development
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Correct Answer: a) Increased movement efficiency
Explanation: Segmentation enables specialized body segments for different functions. In annelids, some segments might be optimized for crawling or burrowing, enhancing movement efficiency. Further specialization of segmented body parts contributed to the evolution of jointed appendages in arthropods.
Q24. Which animal phyla is known for prominent segmentation, both externally and internally?
a) Cnidaria
b) Annelida
c) Porifera
d) Chordata
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Correct Answer: b) Annelida
Explanation: Annelids (segmented worms) are distinguished by segmentation. Segmentation is visible both externally and in the arrangement of internal organs. Metamerism in annelids allows for greater movement complexity and specialization of body regions.
Q25. In segmented animals, each segment often has its own:
a) Coelom
b) Sets of nerve ganglia
c) Excretory organs
d) All of the above
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Correct Answer: d) All of the above
Explanation: Segmented animals often have repeated units of internal organs within each segment. This includes sets of nerve ganglia for control, excretory organs for waste removal, and portions of the coelom, creating a high degree of compartmentalization.
Q26. The flexible, rod-like structure defining the phylum Chordata is the:
a) Jointed appendage
b) Notochord
c) Exoskeleton
d) Water vascular system
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Correct Answer: b) Notochord
Explanation: The notochord is a unique feature of chordates. This rod provides support to the body and serves as an anchor point for muscles. The notochord is present at some developmental stage in all chordates.
Q27. Which of the following is NOT a characteristic of chordates?
a) Post-anal tail
b) Pharyngeal slits
c) Dorsal, hollow nerve cord
d) Jointed exoskeleton
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Correct Answer: d) Jointed exoskeleton
Explanation: Exoskeletons are a defining feature of arthropods, not chordates. Chordates have an internal skeleton and possess features like post-anal tail, pharyngeal slits, and a dorsal nerve cord at some point in development.
Q28. The notochord in most vertebrates is replaced during development by the:
a) Brain
b) Vertebral column
c) Spinal cord
d) Exoskeleton
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Correct Answer: b) Vertebral column
Explanation: The notochord serves as a precursor to the vertebral column in vertebrates. As the embryo develops, the vertebral column forms around the notochord, eventually replacing it to provide the main skeletal support in adults.
Q29. Invertebrates like lancelets (subphylum Cephalochordata) possess a notochord that:
a) Disappears during development
b) Persists throughout their life
c) Develops into a vertebral column
d) Is replaced by an exoskeleton
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Correct Answer: b) Persists throughout their life
Explanation: Lancelets, like other cephalochordates, retain their notochord into adulthood. The notochord provides the main support structure and extends along the length of the body. They lack a true vertebral column.
Q30. Tunicates possess a notochord in their:
a) Adult stage
b) Larval stage
c) Early embryonic stages
d) Tunicates never have a notochord
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Correct Answer: b) Larval stage
Explanation: Tunicates are marine invertebrates within the phylum Chordata. They display a notochord in their free-swimming larval stage, a key chordate feature. However, the notochord is lost during metamorphosis into sessile adults.