1. Explain the major characteristics of the phylum Porifera.
Answer:
- Body Structure: Sponges have a porous body with numerous tiny openings called ostia and a large opening called osculum for water circulation.
- Cellular Organization: They have a cellular level of organization and lack true tissues and organs.
- Symmetry: Asymmetrical or radially symmetrical.
- Skeleton: Supported by spicules or spongin fibers.
- Reproduction: Both sexual (gametes) and asexual (budding and gemmules).
2. Describe the water canal system in sponges.
Answer:
- Water enters through ostia, flows into the spongocoel via canals, and exits through the osculum.
- Types of Canals: Asconoid (simple), Syconoid (folded walls), and Leuconoid (complex network).
- Choanocytes (collar cells) generate water currents and trap food particles.
3. Discuss the life cycle and importance of Cnidarians.
Answer:
- Life Cycle: Alternation of generations between polyp (asexual) and medusa (sexual) forms.
- Reproduction: Polyps reproduce by budding; medusae release gametes for external fertilization.
- Importance: Serve as food sources, form coral reefs, and have applications in biotechnology and medicine.
4. Compare diploblastic and triploblastic organisms.
Answer:
- Diploblastic: Two germ layers (ectoderm and endoderm), e.g., Cnidaria.
- Triploblastic: Three germ layers (ectoderm, mesoderm, and endoderm), e.g., Annelida, Arthropoda.
- Triploblastic organisms show more complexity with specialized organs.
5. Describe the adaptations of flatworms (Platyhelminthes) for parasitism.
Answer:
- Body Structure: Flattened body aids attachment and mobility in host tissues.
- Digestive System: Reduced or absent; rely on host’s nutrients.
- Reproductive System: Highly developed, producing large numbers of eggs.
- Protective Covering: Tegument resists host digestive enzymes and immune responses.
6. What are the distinguishing features of phylum Nematoda?
Answer:
- Body Shape: Cylindrical, elongated, and unsegmented.
- Symmetry: Bilateral.
- Pseudocoelom: Acts as a hydrostatic skeleton.
- Digestive System: Complete with a separate mouth and anus.
- Reproduction: Dioecious, with internal fertilization.
7. Explain the segmentation in annelids and its advantages.
Answer:
- Segmentation: Body divided into metameres, each with similar organs.
- Advantages: Facilitates movement (independent muscle control), repair (damage to one segment does not affect others), and specialization of segments for functions.
8. Discuss the role of the water vascular system in Echinoderms.
Answer:
- Structure: Network of canals (madreporite, ring canal, radial canals, ampullae) connected to tube feet.
- Functions: Movement, respiration, food capture, and excretion.
9. How do arthropods exhibit adaptability to diverse environments?
Answer:
- Exoskeleton: Provides protection and prevents water loss.
- Jointed Appendages: Allow versatile movements.
- Respiratory Systems: Tracheae, gills, or book lungs adapted to terrestrial or aquatic environments.
- Metamorphosis: Reduces competition between juvenile and adult stages.
10. Describe the unique features of mollusks.
Answer:
- Body Plan: Head, muscular foot, and visceral mass.
- Mantle: Secretes shell and forms a mantle cavity for respiration.
- Radula: Feeding structure for scraping food.
- Circulation: Open in most; closed in cephalopods.
11. Explain the significance of coelom in animals.
Answer:
- Definition: Fluid-filled cavity between body wall and gut.
- Significance: Acts as a hydrostatic skeleton, provides space for organ development, and aids in efficient circulation of nutrients and waste.
12. How do chordates differ from non-chordates?
Answer:
- Notochord: Present in chordates, absent in non-chordates.
- Dorsal Nerve Cord: Hollow in chordates, ventral and solid in non-chordates.
- Pharyngeal Slits: Present in chordates, absent or modified in non-chordates.
- Post-Anal Tail: Seen in chordates but not in non-chordates.
13. What is the role of the notochord in chordates?
Answer:
- Provides skeletal support during embryonic development.
- Acts as an axis for muscle attachment.
- In vertebrates, it is replaced by the vertebral column.
14. Discuss the adaptations of amphibians for terrestrial and aquatic life.
Answer:
- Skin: Moist for cutaneous respiration.
- Limbs: Adapted for locomotion on land.
- Respiration: Lungs for terrestrial and gills for aquatic phases.
- Reproduction: Depend on water for egg-laying and larval development.
15. Describe the diversity of reptiles.
Answer:
- Includes turtles, crocodiles, lizards, and snakes.
- Adaptations: Scaly skin prevents water loss; lungs for respiration.
- Reproduction: Internal fertilization, amniotic eggs with shells.
16. How are birds adapted for flight?
Answer:
- Feathers: Lightweight, provide lift and insulation.
- Skeletal System: Hollow bones reduce weight.
- Respiratory System: Air sacs ensure a continuous oxygen supply.
- Muscular System: Strong pectoral muscles for wing movement.
17. Explain the distinguishing characteristics of mammals.
Answer:
- Body Covering: Hair or fur for insulation.
- Mammary Glands: Produce milk for offspring nourishment.
- Endothermy: Maintain constant body temperature.
- Advanced Nervous System: Includes a highly developed brain.
18. What is the significance of pharyngeal slits in chordates?
Answer:
- Function as gills in aquatic species.
- Modified for filter feeding in invertebrate chordates.
- In terrestrial vertebrates, contribute to jaw and ear development.
19. Compare cartilaginous and bony fishes.
Answer:
- Cartilaginous Fishes: Skeleton made of cartilage (e.g., sharks); no swim bladder.
- Bony Fishes: Skeleton made of bone; have swim bladder for buoyancy (e.g., salmon).
20. Describe the evolutionary significance of vertebrates.
Answer:
- Body Plan: Internal skeleton with vertebral column provides structural support.
- Complex Systems: Advanced nervous, circulatory, and respiratory systems.
- Diversity: Occupy various habitats, showing adaptability and evolutionary success.
