ChondrichthyesChondrichthyes

HydrodynamicsHydrodynamics

Body shapeBody shape Sharks typically have an elongate fusiform Sharks typically have an elongate fusiform

body (rounded and tapering at both ends). body (rounded and tapering at both ends). This body shape reduces drag and This body shape reduces drag and requires a minimum of energy to swim. requires a minimum of energy to swim. Swimming is essential for buoyancy.Swimming is essential for buoyancy.

Caudal Fin = PropulsionCaudal Fin = Propulsion

Unlike most bony fishes, the upper lobe of a Unlike most bony fishes, the upper lobe of a shark's caudal fin is larger than the lower shark's caudal fin is larger than the lower lobe. As the caudal fin moves back and lobe. As the caudal fin moves back and forth to propel the shark forward, it also forth to propel the shark forward, it also moves upward. As the caudal fin continues moves upward. As the caudal fin continues to lift, the shark's head points down. The to lift, the shark's head points down. The overall effect of the motion of the caudal fin overall effect of the motion of the caudal fin results in a forward and downward motion results in a forward and downward motion

Pectoral Fins = LiftPectoral Fins = Lift The pectoral fins compensate for this The pectoral fins compensate for this

downward motion. One function of the downward motion. One function of the rigid pectoral fins is to provide lift in the rigid pectoral fins is to provide lift in the forward region of the shark's body. This forward region of the shark's body. This counteracts the overall downward force counteracts the overall downward force caused by the caudal fin and results in caused by the caudal fin and results in horizontal passage through the water.horizontal passage through the water.

Pelvic Fins = balancePelvic Fins = balance

Also PairedAlso Paired In males the median part of the pelvic fin is In males the median part of the pelvic fin is

modified to form a clasper which is used in modified to form a clasper which is used in copulation.copulation.

Swimming SpeedSwimming Speed

Generally sharks swim at speeds less Generally sharks swim at speeds less than 5 kph (about 3 mph). For the most than 5 kph (about 3 mph). For the most part, bottom-dwelling sharks are slow-part, bottom-dwelling sharks are slow-swimming. swimming. Makos are among the fastest sharks, Makos are among the fastest sharks,

reaching speeds up to 48 kph (30 mph).reaching speeds up to 48 kph (30 mph).

CharacteristicsCharacteristics 1. 1. Endoskeleton entirely cartilaginousEndoskeleton entirely cartilaginous..

This is interesting considering they evolved This is interesting considering they evolved from ancestors that had bone.from ancestors that had bone.

Notochord present but reducedNotochord present but reduced

Vertebrae separate and completeVertebrae separate and complete 2. Brain of two olfactory lobes, two optical lobes, 2. Brain of two olfactory lobes, two optical lobes,

two cerebral hemispheres, cerebellum, and two cerebral hemispheres, cerebellum, and medulla oblongata. medulla oblongata.

3. Circulatory System 3. Circulatory System 2 chambered2 chambered heart. heart. 4. Respiration: through gills, they have 5 to 7 4. Respiration: through gills, they have 5 to 7

pairs. pairs.

Placoid ScalesPlacoid Scales

5. Skin with 5. Skin with placoid scales.placoid scales.

Teeth are modified placoid scales that can Teeth are modified placoid scales that can be replaced on a regular basis.be replaced on a regular basis.

Scales Help Swimming?Scales Help Swimming?

As a shark swims, placoid scales As a shark swims, placoid scales may create a series of vortices or may create a series of vortices or whirlpools behind each scale. whirlpools behind each scale. This enables a shark to swim This enables a shark to swim efficiently.efficiently.

66. Digestive System with stomach and . Digestive System with stomach and intestine with a spiral valve.intestine with a spiral valve.

7. Body fusiform with heterocercal 7. Body fusiform with heterocercal caudal caudal fin.fin.8. Mesonephric Kidney and rectal 8. Mesonephric Kidney and rectal gland: the rectal gland helps control salt gland: the rectal gland helps control salt concentrations in the blood by secreting concentrations in the blood by secreting a colorless fluid high in sodium chloride. a colorless fluid high in sodium chloride.

9. No swim bladder or lung. Sharks have 9. No swim bladder or lung. Sharks have high amounts of lipids fats in their high amounts of lipids fats in their

liver liver that help them be bouyant.that help them be bouyant.

10. Separate Sexes10. Separate Sexes All sharks have Internal Fertilization but All sharks have Internal Fertilization but

care of young varies considerably. care of young varies considerably. Oviparous:Oviparous: eggs released by females, eggs released by females,

development outside the mother. development outside the mother. OvoviviparousOvoviviparous: eggs develop inside : eggs develop inside

mother without nourishment from parent. mother without nourishment from parent. Hatch inside mother or immediately after Hatch inside mother or immediately after laying.laying.

Viviparous: Viviparous: eggs develop inside with eggs develop inside with nourishment, offspring born alive already nourishment, offspring born alive already with development.with development.

11. Lateral Line11. Lateral Line: part of its nervous : part of its nervous system. Detects changes of current in the system. Detects changes of current in the water, and movement of some objects in water, and movement of some objects in the water.the water.

Consists of long recessed grooves along Consists of long recessed grooves along the side of the shark. Concentrated at the the side of the shark. Concentrated at the head area and extending posterior to the head area and extending posterior to the tail. The groove has a series of tail. The groove has a series of neuromasts.neuromasts.

Navigation is the primary function of the Navigation is the primary function of the lateral line system.lateral line system.

12. Ampullary 12. Ampullary Organs of LorenziniOrgans of Lorenzini

Detect bioelectric Detect bioelectric fields.fields.

Located in the head Located in the head around the eye.around the eye.

Enables them to detect Enables them to detect prey that is even buried prey that is even buried in the sand.in the sand.