Questions and Answers
What is a distinguishing feature of Elasmobranchs concerning their skeleton?
Which of the following statements is true about Elasmobranch gills?
What unique organ do male Elasmobranchs have associated with their pelvic fins?
How do Elasmobranchs achieve buoyancy in the water?
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What characteristic distinguishes placoid scales found in Elasmobranchs?
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Elasmobranchs have a skeleton made of ______, with no bone tissue.
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The male pelvic fin of Elasmobranchs contains a copulation organ known as ______.
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Elasmobranchs lack a swim bladder and rely on their ______ for buoyancy.
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Unlike Holocephali, Elasmobranchii, which includes sharks, rays, and skates, do not have a ______ covering.
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Elasmobranchs exhibit ______ scales, which are unique to this group.
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Which of the following best describes ovoviviparity in sharks?
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All sharks have a gestation period of 12 months or less.
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Which of the following statements about shark reproduction is true?
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What term describes sharks that produce live young with nutrients supplied by the mother through a placenta?
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Name a shark species that exhibits ovoviviparity and provide one detail about its reproductive traits.
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Approximately ______% of sharks are oviparous, laying eggs that have multiple layers and cord-like growths.
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Which of the following characteristics is associated with endothermic sharks?
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There are 'pure' herbivorous sharks.
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What is the primary advantage of endothermic sharks in terms of predation?
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Carcharhiniformes consist of approximately ______ species.
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What is the maximum depth known for Portuguese Dogfish?
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Bull Sharks are exclusively freshwater species.
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Name a river shark.
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What is the primary function of the Ampullae of Lorenzini in sharks?
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Sharks use their lateral line system to directly see prey.
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What is the role of the rectus muscles in a shark's vision?
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Which term describes the behavior of sharks returning to their exact birthplace for reproduction?
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All sharks exhibit site fidelity by staying in one area for extended time periods.
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What is the term for the behavior of sharks returning to their previous locations after making a long-distance move?
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Some sharks return to their known ______ region for parturition or mating.
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Match the following terms related to shark behavior with their descriptions:
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Study Notes
Elasmobranch Overview
- Composed of cartilage instead of bone, with exceptions for the jaw and teeth.
- Characterized by ventral nasal openings and mouth placement; some species exhibit more terminal mouths.
- Possess true upper and lower jaws, enhancing feeding capabilities.
Reproductive Adaptations
- Males have a modified pelvic fin known as copulation organ (mixopterygium or clasper) for mating.
Physiological Features
- Lacks a swim bladder, relying on liver for buoyancy control.
- Includes two main subclasses:
- Holocephali (Chimeras): Features soft gill covers protecting four gill openings.
- Elasmobranchii (Sharks, Rays, and Skates): Lacks gill covers, has 5-7 exposed gills, and may have absent spiracles.
Respiratory Adaptations
- Not all shark species need to continuously swim to breathe, demonstrating varied respiratory adaptations.
Other Characteristics
- Features a unique dental adaptation with permanent tooth replacement throughout its life.
- Skin is covered in placoid scales, contributing to reduced drag and protection.
Elasmobranch Overview
- Composed of cartilage instead of bone, with exceptions for the jaw and teeth.
- Characterized by ventral nasal openings and mouth placement; some species exhibit more terminal mouths.
- Possess true upper and lower jaws, enhancing feeding capabilities.
Reproductive Adaptations
- Males have a modified pelvic fin known as copulation organ (mixopterygium or clasper) for mating.
Physiological Features
- Lacks a swim bladder, relying on liver for buoyancy control.
- Includes two main subclasses:
- Holocephali (Chimeras): Features soft gill covers protecting four gill openings.
- Elasmobranchii (Sharks, Rays, and Skates): Lacks gill covers, has 5-7 exposed gills, and may have absent spiracles.
Respiratory Adaptations
- Not all shark species need to continuously swim to breathe, demonstrating varied respiratory adaptations.
Other Characteristics
- Features a unique dental adaptation with permanent tooth replacement throughout its life.
- Skin is covered in placoid scales, contributing to reduced drag and protection.
Reproductive Methods in Sharks
- Internal fertilization is the primary method for shark reproduction.
- Variation in mating habits: Different shark species have specific preferences for mating locations and seasonal timing; some species mate year-round.
Gestation and Resting Periods
- Sharks often experience resting periods of 1-3 years between reproduction cycles.
- Gestation time varies significantly, typically between 6-24 months.
Types of Reproduction
-
Oviparous:
- Approximately 40% of sharks and all skates lay eggs.
- Egg cases are multi-layered with cord-like growths for anchoring, measuring between 10cm to 25cm in length.
- Egg capsules contain yolk for embryo nourishment.
-
Ovoviviparous (Aplacental viviparity):
- Embryos develop inside an egg, but live young are born; the single egg yolk provides all nutrition.
-
Viviparous (Placental viviparity):
- In all rays, embryos develop in a yolk sac that then forms a placenta.
- Embryos receive nutrients via a placental cord from the mother, resulting in live births.
Survival and Young Production
- Sharks typically give birth to a few large young, which enhances their survival chances.
Species-Specific Reproductive Strategies
-
Sand Tiger Shark:
- Exhibits ovoviviparity; embryos initially feed on the mother's unfertilized eggs (oophagy) and later on sibling embryos (adelphophagy).
- Produces live offspring with an average length of about 100cm.
-
Whale Shark:
- Also follows ovoviviparity; can give live birth to as many as 300 young, each measuring 55-65cm at birth.
Reproductive Methods in Sharks
- Internal fertilization is the primary method for shark reproduction.
- Variation in mating habits: Different shark species have specific preferences for mating locations and seasonal timing; some species mate year-round.
Gestation and Resting Periods
- Sharks often experience resting periods of 1-3 years between reproduction cycles.
- Gestation time varies significantly, typically between 6-24 months.
Types of Reproduction
-
Oviparous:
- Approximately 40% of sharks and all skates lay eggs.
- Egg cases are multi-layered with cord-like growths for anchoring, measuring between 10cm to 25cm in length.
- Egg capsules contain yolk for embryo nourishment.
-
Ovoviviparous (Aplacental viviparity):
- Embryos develop inside an egg, but live young are born; the single egg yolk provides all nutrition.
-
Viviparous (Placental viviparity):
- In all rays, embryos develop in a yolk sac that then forms a placenta.
- Embryos receive nutrients via a placental cord from the mother, resulting in live births.
Survival and Young Production
- Sharks typically give birth to a few large young, which enhances their survival chances.
Species-Specific Reproductive Strategies
-
Sand Tiger Shark:
- Exhibits ovoviviparity; embryos initially feed on the mother's unfertilized eggs (oophagy) and later on sibling embryos (adelphophagy).
- Produces live offspring with an average length of about 100cm.
-
Whale Shark:
- Also follows ovoviviparity; can give live birth to as many as 300 young, each measuring 55-65cm at birth.
Diversity of Sharks
- Carcharhiniformes is a diverse group containing approximately 282 species.
- No sharks are classified as "pure" herbivores; they all exhibit carnivorous or omnivorous feeding habits.
- Ectoparasitic sharks exist, highlighting the varied ecological roles sharks play in marine environments.
Endothermic Sharks
- Notable examples of partially warm-blooded sharks include Threshers, Porbeagle, Makos, and White sharks.
- Endothermic characteristics enhance predation efficiency due to increased body temperature, facilitated by a specialized structure known as rete mirabile.
- Heat is generated by muscular activity, creating a contraflow heat exchange that warms the body and boosts metabolic rates.
- Higher metabolic rates in endothermic sharks necessitate consuming up to 10 times more food compared to their ectothermic counterparts.
Longevity of Shark Species
- Some species of sharks that existed millions of years ago are still present in today’s oceans, indicating their resilience and adaptability through time.
Shark Distribution
- Sharks typically avoid abyssal regions, depths exceeding 3000 meters, with rare exceptions noted.
- The Portuguese Dogfish usually inhabits depths ranging from 400 to 2000 meters but has been recorded at a remarkable depth of 3675 meters.
- Certain shark species, such as the Blue Shark, have a global distribution, found in various oceans around the world.
- River sharks, including the Ganges Shark, thrive in freshwater environments, showcasing adaptability outside of marine settings.
- Freshwater rays like the Ocellate River Stingray are also present in river systems, emphasizing the diversity of elasmobranchs in non-salty waters.
- Bull Sharks are notable for their unique ability to navigate and survive in both marine and freshwater ecosystems.
Sensory Abilities of Sharks
- Sharks are particularly attracted to irregular low-frequency pulse signals, aiding in their hunting capabilities.
- They can learn to associate specific sounds with the presence of food, enhancing their foraging efficiency.
- The sense of smell is crucial for sharks, used for locating prey and potentially identifying mating partners. They can determine the direction of scents by moving their heads.
Visual and Physical Adaptations
- Sharks possess well-developed, large, and complex eyes enabling effective vision underwater.
- The rectus muscles in their eyes allow sharks to focus by adjusting the position of the lens in relation to the retina.
Lateral Line System
- Sharks utilize the Lateral Line System as a means of distant touch, which helps them detect water displacements caused by nearby prey.
- This system consists of small pores leading to fluid-filled channels beneath the skin.
- Changes in water pressure trigger tiny hairs within these channels to move, sending electric signals to the brain for processing.
Electroreception
- Ampullae of Lorenzini function as specialized electroreceptors, allowing sharks to detect electric fields in the water.
- Pores located around the snout have developed heightened sensitivity to electric pulses. Each pore is filled with a gelatinous substance, and below each pore is a sensory nerve that transmits electric signals to the brain.
Shark Behavior Patterns
- Residency: Certain shark species demonstrate long-term presence in specific areas, indicating a strong attachment to localized habitats.
- Site Fidelity: Some sharks exhibit a tendency to return to a previously visited area after traveling significant distances, showcasing their navigational skills and environmental memory.
- Natal Philopatry: This behavior is characterized by sharks returning to their exact birthplace for reproductive purposes, highlighting the importance of specific habitats in their life cycle.
- Regional Philopatry: Sharks may also return to specific regions where they were born for mating or birthing, indicating a broader geographic loyalty to certain areas rather than precise locations.
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Description
Dive into the fascinating world of elasmobranchs, the group of cartilaginous fish that includes sharks, rays, and skates. This quiz covers their unique anatomical features such as the absence of a swim bladder, their reproductive organs, and gill structures. Test your knowledge and learn more about these remarkable marine creatures.
