Free Biodiversity and Variety of Life MCQs with Answers

2731. Stretch receptors are present in _ of tetrapods

• A. Tendons and joint capsules
• B. Thorax
• C. Antennae
• D. Abdomen

Explanation: Stretch receptors are mechanoreceptors responsive to the distention of various organs and muscles and are neurologically linked to the medulla in the brain stem via afferent nerve fibers. Stretch receptors called Golgi tendon organs are found within the collagen fibers of tendons and within joint capsules in tetrapods. They are generally located in series with the muscle rather than the parallel arrangement of the intrafusal muscle fibers.

2732. The larva formed during the life cycle of annelida is

• A. Glochidium larva
• B. Bipinnaria larva
• C. Trochophore larva
• D. Tomaria larva

Explanation: Trochophore, also called trochosphere, small, translucent, free-swimming larva characteristic of marine annelids and most groups of mollusks and it is commonly formed during life cycle of annelida

2733. Platyhelminthes are

• A. Bilaterally symmetrical and diploblastic
• B. Bilaterally symmetrical and triploblastic
• C. Radially symmetrical and triploblastic
• D. Radially symmetrical and diploblastic

Explanation: Phylum Platyhelminthes belongs to the kingdom Animalia. This phylum includes 13,000 species. The organisms are also known as flatworms. Platyhelminthes are triploblastic, bilaterally symmetrical. They may be free-living or parasites. The body has a soft covering with or without cilia. They respire by simple diffusion through the body surface. They are devoid of the anus and circulatory system but have a mouth etc.

2734. The deuterostomes differ from protostomes in all of the following respects EXCEPT:

• A. Early cleavages of the zygote
• B. Ultimate function of the opening to the archenteron
• C. Number of germ layers in the developing embryo
• D. Embryonic origin of the mouth
• E. embryonic origin of the coelom

Explanation: Both deuterostomes and protostomes have three germ layers. The statement that is NOT true among the given options is: "number of germ layers in the developing embryo" Deuterostomes and protostomes both have three germ layers (ectoderm, mesoderm, and endoderm) in the developing embryo. This is a shared characteristic between these two groups of animals. The distinction between deuterostomes and protostomes lies in other aspects, as listed in the options.

2735. Species of Phylum Platyhelminthes are:

• A. Roundworms
• B. Flatworms
• C. Hookworms
• D. Threadworms
• E. Pinworms

Explanation: The phylum Platyhelminthes consists of flatworms, which are named for their flat, dorsoventrally flattened bodies. This sets them apart from other worm-like organisms, such as roundworms (Nematoda), which have a cylindrical shape. Flatworms are simple, unsegmented invertebrates with bilateral symmetry. Other options like hookworms, threadworms, and pinworms are all roundworms and do not belong to the Platyhelminthes phylum.

2736. Scales are present in:

• A. Fishes
• B. Reptiles
• C. Birds
• D. Amphibians
• E. A B and C

Explanation: The skin of most fishes is covered with scales. Placoid scales in sharks and rays, cosmoid scales in lungfishes and some fossil fishes, ganoid scales in bichirs, bowfin, paddle fishes, gars, sturgeons, cycloid and ctenoid scales in most bony fishes. Reptile skin is also covered with scutes or scales. Scales are made of keratin and are formed from the epidermis. They may be ossified or tubercular, as in the case of lizards, or modified elaborately, as in the case of snakes.

2737. Salamander belongs to which of the following class?

• A. Pisces
• B. Aves
• C. Reptiles
• D. Amphibians

Explanation: Amphibia is a class of vertebrates that includes frogs, toads, newts, and salamanders. These animals are adapted to a semi-aquatic lifestyle, as they spend part of their lives in water and part on land. Salamanders are specifically known for their ability to regenerate lost body parts, including limbs and tails.

2738. Vertebrates belong to phylum chordata because:

• A. They have a vertebral column
• B. The brain is enclosed by the skull
• C. The embryos have gills
• D. All of these

Explanation: Vertebrates belong to phylum Chordata primarily because they exhibit several defining features, including a vertebral column (backbone), a brain protected by a skull, and the presence of gill structures during embryonic development. Each of these characteristics is critical for the classification of organisms within this phylum. Option A, stating they have a vertebral column, is true but incomplete on its own. Option B highlights the protective feature of the skull, which is also true but does not encompass all the defining traits. Option C mentions the embryonic gills, which is a trait present in many vertebrates, but again does not capture the full spectrum of characteristics. Therefore, Option D, 'All of these', is the correct answer as it encompasses all the essential features that classify vertebrates in the phylum Chordata.

2739. Which of the following are believed to have common origin with annelids?

• A. Nematodes
• B. Arthropods
• C. Molluscs
• D. None of these

Explanation: Arthropods are believed to have a common origin with annelids. Arthropods, which include insects, spiders, crustaceans, and other joint-legged animals, belong to the phylum Arthropoda. While both arthropods and annelids are segmented animals, they are part of different phyla and have significant differences in body structure and developmental patterns.

2740. Mantle in molluscs is present over which of the following regions?

• A. Head
• B. Dorsal muscular foot
• C. Dorsal visceral body
• D. Both A and B

Explanation: The correct option is C. The mantle in molluscs is a significant anatomical feature that forms a protective layer over the dorsal visceral body, which contains the internal organs. The mantle is often involved in secreting the shell in species that possess one. It is not associated with the head or the muscular foot, which are primarily involved in sensory functions and locomotion, respectively.