Questions and Answers
What is the texture of shark skin?
What helps sharks maneuver and provides stabilization?
Fins
Match the types of fins with their names:
Pectoral = Paired fins Pelvic = Paired fins Dorsal = Unpaired fins Caudal = Unpaired fins Anal = Unpaired fins
How many gills do sharks have?
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What type of reproduction do sharks exhibit?
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The skeleton of a shark is primarily bony.
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What is the appearance of shark coloration known as?
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The ______ contains sensory structures and the brain in sharks.
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What does the spiral valve do in a shark?
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What is the structure that allows sharks to detect water current and pressure?
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Sharks have no need for nostrils.
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What distinctive feature does the caudal fin of a shark have?
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What type of canal passes through the neural arch of a shark's vertebral column?
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What is the function of the spiral valve in the digestive system of sharks?
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Study Notes
Class Chondrichthyes Overview
- Chondrichthyes includes sharks, rays, and skates, characterized by a cartilaginous skeleton.
Skin
- Tough and abrasive texture, covered with placoid scales and mucous glands.
Fins
- Essential for maneuvering and stabilization in aquatic environments.
- Paired fins: Include pectoral and pelvic fins.
- Unpaired fins: Two dorsal fins, a caudal fin, and an anal fin.
Mouth & Jaws
- Positioned subterminally (not at the end) and ventrally.
Teeth
- Replaceable throughout life; composed of an outer layer of enamel, dentine, and pulp.
Nostrils
- Function as blind olfactory sacs, not connected to the mouth.
Digestive System
- Contains a spiral valve in the intestines to increase surface area for nutrient absorption.
Skeleton
- Composed of cartilage, strengthened by calcium deposits, with remnants of the notochord throughout life.
Gills and Respiration
- Sharks possess five gills.
- Gill slits allow water intake for respiration.
Nervous System
- 10 cranial nerves present, supporting diverse sensory functions.
- The ear structure includes three pairs of semicircular canals for balance.
Reproductive Traits
- Dioecious (separate sexes) with internal fertilization; cloaca present.
- Oviparous, with eggs rich in yolk, undergoing direct development without metamorphosis.
Habitat
- Primarily marine species, though some like bull sharks inhabit freshwater environments.
Body Shape
- Fusiform body: tapered at both ends, aiding in streamlined movement.
Sensory Structures
- Head contains sensory organs and brain.
- Coloration features countershading—dark on top and light on the underside for camouflage.
- Lateral line system detects water currents and pressure changes.
Caudal Fin
- Heterocercal structure, where the top lobe is larger than the bottom, enhancing lift.
Claspers
- Male sharks possess claspers for sperm transfer during mating.
Special Features
- Spiracles serve as modified gill slits, allowing water passage to the pharynx and supplying oxygen to the eye and brain.
Skeletal Divisions
- Axial division: Includes the cranium and vertebrae.
- Appendicular division: Comprises fin supports and supportive girdles.
- Centrum division: Forms around the notochord and is crucial for structural integrity.
Vertebral Column Structure
- Neural arch: Located above the centrum, allowing spinal cord passage through the neural canal.
- Haemal arch: Found below the centrum in caudal vertebrae, facilitating blood vessel passage.
- Transverse processes: Projects to the sides, found only in trunk vertebrae.
Cranium and Facial Features
- Cartilaginous case known as chondrocranium, encasing the brain and senses.
- Rostrum acts as the anterior projection or snout.
- Olfactory capsules located at the rostrum's sides house smell receptors.
- Orbit, behind the olfactory capsule, contains the eye; otic region houses semicircular canals for balance.
- Occipital region includes the foramen magnum, a crucial opening connecting the brain and spinal cord.
Visceral Structures
- Splanchnocranium composed of seven visceral arches; the mandibular arch is the first and contains the jaw.
- Hyoid arch serves as the second visceral arch, supporting the structure of the throat.
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Description
Test your knowledge on Chondrichthyes with these flashcards. Each card covers essential terms and characteristics such as skin features, fins, and mouth structure. Perfect for biology students and marine life enthusiasts!
