Time: 3 hrs
Max. Marks: 75
Section-A
I. Answer any five questions of the following. 5×3=15 Marks
- Elphidium
Elphidium is a genus of foraminifera, which are single-celled marine organisms with a shell (test). The shells are typically made of calcium carbonate and have a distinctive chambered structure. These organisms play an important role in marine ecosystems, as they serve as food for other organisms and contribute to sediment formation. Elphidium species are used in paleoenvironmental studies to infer past oceanic conditions. - Spongocoel
The spongocoel is the central cavity of a sponge (phylum Porifera), where water is drawn in through pores (ostia) for feeding and gas exchange. The water flows through the spongocoel and exits through a larger opening called the osculum. The spongocoel’s role is to provide a space for the circulation of water, which helps in nutrient absorption, waste removal, and respiration. - Siphonophora
Siphonophora is a class of colonial, marine invertebrates within the phylum Cnidaria. These animals are composed of specialized polyps and medusoids that work together as a single organism. Some species, such as Praya Dubia, can grow to extreme lengths. They are notable for their complex colony structure, where different individuals perform various functions such as feeding, defense, and reproduction. - Schistosoma
Schistosoma is a genus of parasitic flatworms that cause the disease schistosomiasis. The life cycle of Schistosoma involves multiple hosts, including snails and humans. The larvae penetrate the skin of humans when they come in contact with contaminated water, mature in the liver, and release eggs that are excreted in feces or urine. The eggs can cause tissue damage and lead to severe health issues. - Hirudin
Hirudin is an anticoagulant protein found in the saliva of leeches, such as Hirudo medicinalis. It prevents blood clotting by inhibiting thrombin, the enzyme that causes blood to clot. Hirudin has been studied for its medicinal properties, particularly in preventing thrombosis (formation of blood clots) and as a potential therapeutic agent in cardiovascular diseases. - Silkworm
The silkworm (Bombyx mori) is an insect known for producing silk fibers, which are harvested for use in textiles. The larvae of the silkworm spin a protective cocoon around themselves using silk secreted from specialized glands. The life cycle of the silkworm includes egg, larval (caterpillar) stage, pupa (cocoon), and adult (moth) stage. Silkworms are also important in the study of genetics and development. - Radula
The radula is a specialized feeding organ found in many mollusks, including snails, slugs, and some bivalves. It is a chitinous structure covered with rows of microscopic teeth, which are used to scrape, cut, or tear food before ingestion. The radula is unique to mollusks and plays an essential role in their feeding habits, particularly in herbivorous and carnivorous species. - Ophiopleuteus
Ophiopleuteus is a genus of brittle stars (class Ophiuroidea), which are echinoderms closely related to starfish. These animals are characterized by long, flexible arms that are distinct from the central disc, and they are often found in deep-sea habitats. They are scavengers and feed on detritus and small organisms. Brittle stars move by bending their arms and are important in marine ecosystems for their role in nutrient cycling.
Section-B
II. Answer the following questions. 4 x 15 = 60 Marks
- a). Discuss the reproduction in Protozoa
Protozoa are single-celled eukaryotic organisms that exhibit a wide range of reproductive strategies, both sexual and asexual.
- Asexual Reproduction: Most protozoa reproduce asexually by binary fission, where the cell divides into two genetically identical offspring. Some protozoans, like amoebas, can also reproduce by budding or schizogony, where multiple fission results in several offspring from a single organism.
- Sexual Reproduction: In sexual reproduction, many protozoa undergo a process called conjugation, where two organisms exchange genetic material to increase genetic diversity. This occurs in organisms like Paramecium. Additionally, some protozoans undergo gametogenesis, where haploid gametes fuse to form a diploid zygote, initiating a new generation.
(OR)
b). Describe the types of spicules in sponges
Spicules are skeletal elements found in the bodies of sponges, providing structural support. They are made of either silica or calcium carbonate. The three main types of spicules are:
- Siliceous spicules: Made of silica, these spicules are typically found in glass sponges (class Hexactinellida).
- Calcareous spicules: Composed of calcium carbonate, these spicules are found in sponges of the class Calcarea.
- Spongin: In some sponges, the skeleton is composed of a protein called spongin, which is flexible and provides the sponge with a soft, spongy texture.
- Mixed spicules: Some sponges may have a combination of siliceous, calcareous spicules, and spongin fibers, depending on the species.
- a). Describe the corals and coral reef formation in Cnidarians
Corals are marine invertebrates belonging to the class Anthozoa within the phylum Cnidaria. They form colonies of genetically identical polyps. Corals are known for their ability to produce calcium carbonate skeletons that form the structure of coral reefs. The process of reef formation involves:
- Colonial Growth: Individual polyps secrete calcium carbonate, forming a hard, external skeleton. These polyps continuously reproduce and grow, resulting in the expansion of the reef.
- Symbiosis with Zooxanthellae: Corals have a mutualistic relationship with photosynthetic algae called zooxanthellae. These algae live within the coral’s tissues and provide energy to the corals through photosynthesis, which is crucial for the growth and survival of the reef.
- Types of Reefs: There are three main types of coral reefs: fringing reefs (nearshore reefs), barrier reefs (separated from land by lagoons), and atolls (circular reefs surrounding a lagoon).
(OR)
b). Discuss the life cycle of Schistosoma
The life cycle of Schistosoma is complex and involves multiple hosts:
- Egg Stage: Eggs are excreted through the urine or feces of infected humans.
- Larval Stage: Eggs hatch into larvae called miracidia, which infect snails (intermediate hosts). Inside the snail, they undergo asexual reproduction and transform into cercariae.
- Cercariae Stage: The cercariae are released from the snail and swim in water, where they can penetrate the skin of humans (the definitive host).
- Adult Stage: Once inside the human body, the cercariae develop into adult worms in the blood vessels, where they mate. The female produces eggs that can cause inflammation and tissue damage.
- a). Discuss the digestive system of Hirudinaria granulosa and mention its specialty
The digestive system of Hirudinaria granulosa (a species of leech) is specialized for feeding on blood:
- Mouth: The leech uses a sucker around its mouth to attach to a host and pierce the skin with its specialized jaws or proboscis.
- Pharynx and Esophagus: After attachment, the leech’s pharynx draws in blood from the host.
- Crop: The blood is stored in the crop, a large, expandable organ that can stretch to accommodate large quantities of blood. This allows the leech to feed for extended periods.
- Intestine: The digestive enzymes break down the blood, and nutrients are absorbed in the intestine.
- Specialty: One of the main specialties of Hirudinaria granulosa is its ability to produce the anticoagulant hirudin, which prevents the host’s blood from clotting while the leech feeds.
(OR)
b). Describe the useful and harmful insects
- Useful Insects:
- Pollinators: Bees, butterflies, and other insects pollinate plants, including crops, ensuring the reproduction of many plant species.
- Decomposers: Insects like ants and beetles help break down organic material, recycling nutrients back into ecosystems.
- Predators: Insects like ladybugs control pests by feeding on aphids and other harmful insects.
- Harmful Insects:
- Agricultural Pests: Insects like locusts, aphids, and caterpillars damage crops, leading to significant agricultural losses.
- Disease Vectors: Mosquitoes spread diseases such as malaria, dengue, and Zika. Ticks are vectors for Lyme disease, and fleas spread bubonic plague.
- Wood-Boring Insects: Termites and beetles can destroy wooden structures, leading to severe property damage.
- a). Describe the process of pearl formation in molluscans
Pearl formation in mollusks is a natural defense mechanism:
- Invasion: A foreign particle, such as a grain of sand or a parasite, enters the mollusk’s body.
- Nacre Secretion: The mollusk secretes layers of nacre (mother-of-pearl) around the irritant to protect itself. Nacre is composed of calcium carbonate and conchiolin.
- Layering: Over time, additional layers of nacre are added around the foreign object, forming a pearl.
- Harvesting: In cultured pearl farming, humans insert a small bead or tissue into the mollusk to initiate the formation of a pearl.
(OR)
b). Describe the general characters of Echinoderms and write its classification up to classes
General Characters of Echinoderms:
- Radial Symmetry: Adult echinoderms exhibit radial symmetry, typically pentaradial (five-fold symmetry).
- Calcareous Exoskeleton: They have a hard exoskeleton made of calcium carbonate plates or ossicles.
- Water Vascular System: Echinoderms have a unique water vascular system that aids in movement, feeding, and respiration.
- Spiny Skin: Echinoderms have spines or tubercles on their skin.
- Regeneration: Many echinoderms can regenerate lost body parts.
Classification:
- Phylum: Echinodermata
- Class Asteroidea: Starfish (sea stars).
- Class Ophiuroidea: Brittle stars.
- Class Echinoidea: Sea urchins and sand dollars.
- Class Holothuroidea: Sea cucumbers.
- Class Crinoidea: Sea lilies and feather stars.