### animal | vertebrate | fish:

Shark
* All sharks are carnivores, they hunt for different animals
  - which means that they feed on other animals as opposed to vegetation
  - carnivorous, but their food varies from large ocean creatures to tiny plankton
  - fishes
  - predators, and usually exist at, or close to, the apex of their food chains
  - go to great lengths to protect their developing young before birth
* All sharks have an asymmetric tail fin, with the upper lobe being larger than the lower one
  - extremely powerful jaws to complement their teeth
  - internal fertilization
  - to swim constantly
  - reproduce by internal fertilization
  - swim by moving their vertically oriented tail fin from side to side
* Find out more about how sharks move, sleep, eat, and defend themselves.
* Many sharks actively chase their food.
* Many sharks are efficient and specialized hunters that have thrived for millions of years
  - gentle and eat only plankton
  - like humans and give birth to only one or two babies at a time
  - more active at night, so avoid night swims
  - nocturnal , meaning that they are most active at night
  - small, and eat fish, shellfish, and clams
  - warm blooded
  - can contract and dilate their pupils , like humans, something no teleost fish can do
  - eat pinnipeds, including the great white shark
* Many sharks have a ventral mouth well suited to predatory lifestyle
  - interesting migration patterns which have been discovered through tagging
  - spines on their dorsal fins
* Many sharks live in the deep scattering layer
  - or hunt in reefs
* Many sharks migrate up rivers
  - yearly from cold feeding waters to warm breeding waters
  - prey most often on the weak, inferior members of the population
  - remain on the bottom in a quiescent state
  - reproduce once a year, but there are some that can only do so every other year
  - start life as eggs, from which baby sharks emerge after several months
* Most sharks adapt to habitats.
* Most sharks appear in environments
  - oceans
  - sea
* Most sharks are active predators, some of the large varieities are actually plankton eaters
  - afraid of people
  - carnivorous, though, and can swallow their prey whole
  - cold-blooded
  - dark with pale bellies
  - ectothermic
  - efficient swimmers
  - especially active in the evening and night when they hunt
  - evolved from sharks
  - gray and have a leathery skin
  - harmful to people
  - inside oceans
  - known as sharks
* Most sharks are located in reefs
  - long-lived, grow slowly, mature late and produce few offspring
  - man-eaters
* Most sharks are meat eaters and so they feed on other fish and even other sharks
  - meat-eaters, but the basking shark and the whale shark eat plankton
  - ovoviviparous, hatching the eggs within the female and bearing live young
  - predatory, but only a small number are known to attack humans unprovoked
  - six to seven feet long
  - slow-growing and slow to reproduce
  - smaller and eat small fish and crabs
  - solitary animals, though a few, such as the spiny dogfish shark, form schools
  - very social
  - bear live young, although some species lay eggs with protective horny shells
  - can detect blood and animal odors from many miles away
  - come from sea
  - develop lungs
* Most sharks eat animals
  - bony fish
  - chums
  - fish, squid, marine mammals, and scavenge any other available food source
  - flesh
  - squids
* Most sharks eat their prey whole, or tear off large chunks of flesh at a time
  - or they tear off large chunks of flesh
  - or they tear off large chunks of the bodies
  - tuna
  - victims
* Most sharks feed in bays
* Most sharks feed on animals
  - marine animals
  - small creatures
  - find in gulfs
  - float in water
  - give birth in warm water during the late spring and early summer
* Most sharks give birth to live young, but some release eggs that hatch later
  - live birth
* Most sharks grow brains
  - cells
  - organs
  - stomachs
  - tails
  - to size
* Most sharks has-part bones
  - extremities
  - eyes
  - gills
  - glands
  - lids
  - mouths
  - muscles
  - tissue
* Most sharks have a rounded body shaped like a torpedo
  - tough-skinned, streamlined shaped body, somewhat like a torpedo
  - well-developed sense of vision
  - cartilages
  - density
  - diets
  - eyesights
  - few young and take a long time to mature
* Most sharks have five different kinds of fins, which lift, stabilze and propel the shark
  - types of fins, while some sharks only have four
  - pairs of gill slits, but some have six or seven pairs
  - genus
* Most sharks have good senses
  - vision even though most are nocturnal feeders
  - heads
  - hearts
  - layers
  - livers
  - mechanisms
  - mouths located on the underside of their snout
  - projection surfaces
  - receptors
  - second dorsal fins
  - shape teeth
  - shapes
  - sharp teeth that are used to catch their food
  - sides
  - similar mechanisms
  - snouts
  - soft cartilages
  - specific mating areas
  - tail fins
  - taper tails
  - teeth that differ in the upper and lower jaws
  - tendencies
  - their mouths on the underside of the head
  - thick heads
  - unique shapes
  - variation
* Most sharks have vertical fins
  - hide in reefs
* Most sharks inhabit coastal water
  - shallow water
  - kill prey
* Most sharks live in coasts
  - cold water
* Most sharks live in shallow sea
  - the tropics
  - tropical and temperate inshore waters
  - on reefs
  - only in the marine environment in full-strength saltwater
  - love blood
* Most sharks migrate to gulfs
* Most sharks move eyes
  - never encounter a human being
* Most sharks occur in sea
  - temperate sea
* Most sharks occur in warm sea
* Most sharks play in oceans
* Most sharks possess blood
* Most sharks prefer ocean saltwaters
  - temperate water
  - to eat certain types of invertebrates, fish and other animals
* Most sharks prefer warm saltwaters
  - require food
* Most sharks seek fish
  - seize fish
* Most sharks survive in fresh water
* Most sharks swallow their food whole or bite it into relatively large pieces
  - whole, without chewing
* Most sharks swim by thrusting their tail fins from side to side
  - constantly but leisurely, propelled by the sculling motion of the body and tail
  - continuously
* Most sharks swim in oceans
  - take years to reach sexual maturity and raise few pups in a lifetime
  - use aggression primarily in their quest for prey
* Most sharks wait for fish
* Some sharks are endothermic however
  - even plankton-eaters
  - filter feeders
  - inside aquaria
  - located in coasts
  - member of families
  - only as big as a human hand
  - oviparous , laying their eggs in the water
  - pregnant for two to three years before giving birth
* Some sharks are so rare they lack any common name, having only a scientific name
  - well equipped for eating that they're all teeth
  - avoid predators
  - belong to families
  - bite hands
  - can gulp air into their stomach which can provide some buoyancy
* Some sharks can live for a year without eating, surviving on the oil stored in their livers
  - in oceans, rivers and lakes
  - one year without eating
  - replace their front teeth every two weeks
  - swim very fast
  - use so-called apparent death
  - crush their prey
  - deposit a fertilized egg sac on the ocean floor
  - develop antibodies
  - disappear from feeds for periods of around three months
* Some sharks eat adult sea turtles
  - anything
  - dolphins
  - hatchlings
  - mainly fish
  - octopi
  - shellfishes
  - stingrays
  - urchins
* Some sharks even eat swordfish
  - launch their heads out of the water and can be touched
  - prey on their own kind
* Some sharks feed on plankton
  - whales
* Some sharks give birth to animals
* Some sharks go into tonic immobility when they are turned upsidedown
  - to bays
  - grasp the female pectoral fins, or bite and hold onto the body
* Some sharks grow bones
  - to be only a foot long
  - has-part snouts
  - hatch eggs inside their bodies then give birth to live young
* Some sharks have bamboo sharks
  - concentration
  - cones
  - few natural predators
  - five rows of teeth
  - flat bodies so they can hide in the ocean floor
  - greenish tints
  - large jaws
  - live babies
  - lobes
  - lower lobes
  - molarlike grinding teeth
  - ovaries
  - placentas
  - sensitivity
  - shark pups
  - single ovaries
  - small openings called spiracles behind the eyes at the top of the head
  - spiracles, which are special gill slits located just behind the eyes
  - testes
  - to always swim to maintain buoyancy
  - upper lobes
  - whorls
* Some sharks inhabit coastal regions
* Some sharks kill people
  - surfers
  - live at the bottom of deep underwater canyons
* Some sharks live in gulfs
* Some sharks maintain body temperature
  - migrate over great distances to feed and breed
  - now reside in fake habitats along with other types of aquatic live
* Some sharks only eat each other
  - fish, others only eat crabs, still others only seals
* Some sharks possess antibodies
* Some sharks prey on bottlenose dolphins
  - great hammerheads
  - juvenile hammerheads
  - produce a shell that is tough and can protect the young
  - provide nutrients
  - range in size
* Some sharks reach maturity
  - require aquaria
  - shed layers
  - spread microbes
  - stay in the same region their entire lives while others travel across oceans
  - survive by making their blood as toxic as the surrounding water
  - tend to search for food at night
  - thrive in environments
  - wrap their eggs around plants
* account for just one per cent of all the species fished in the world
  - percent of all the species fished in the world
* also attack humans because they have been provoked or agitated by the person
  - can explain the origins of the immune system in evolution, experts say
  - come in many sizes
  - feed on dead or dying animals
* also have a conveyor belt system of dental replacement
  - lateral line system
  - very acute sense of hearing
  - an acute sense of smell
  - gill slits on their heads rather than gill covers - typically five on each side
  - good eye sight, and hearing
  - large livers full of low-density oils, which provide some buoyancy
* also have very low growth rates, a problem that is compounded by overfishing
  - a problem that is related to the problem of overfishing
  - prefer to attack at dawn or dusk
  - regulate the big parrotfish that feed on coral
  - reveal great diversity in behavior and size
  - seem to use their electrical sense for navigation and migration
  - serve to remove the sick, diseased, weak or injured animals from the ocean
  - show great diversity in size
  - vary in lifestyle
  - withdraw from sounds that have a sudden onset
* apparently are the only animals that never get sick.
* are Elasmobranch fish.
* are a common catch in the spring and summer
  - seafood in many places , including Japan and Australia
  - cosmopolitan species, with many makes and models
  - dolphin's main predator
  - formidable predator throughout the life cycle of the Green Sea Turtle
  - keystone species
  - problem for the Hawaiian monk seal, as are commercial fishing nets
  - second group of marine life that is headed for trouble
* are a type of fish that have no bones, only cartilage
  - valuable fishery for their fins, a delicacy in the Orient
* are a very good example of fusiform predators
  - important part of the balance in the ocean
  - vital part of the overall ecosystem
* are able to pick up very small electrical pulses that all living things emit
  - see color contrasts extremely well
  - abundant along with a large range of pelagic fishes
  - afraid of jet skis
  - almost exclusively marine in distribution
* are also fine to be afraid of
  - the ocean's garbage disposals
  - very, very sensitive to electrical fields
  - amazing fish that have been around since long before the dinosaurs existed
  - among the healthiest creatures on earth
* are among the most biologically vulnerable species in the ocean
  - sensitive to electric currents of all ocean creatures
  - successful and ancient groups of fishes
* are an abundant species and an important food resource throughout the world
  - ancient line of fish
  - important part of the reef ecology
  - integral facet of the ocean environment
  - often misunderstood but very important component of the undersea community
  - old family of fish, dating back many millions of years to the Devonian Period
* are animals that are superbly adapted to their environment
  - with a great deal of cartilage
* are at the top of the food chain
  - ocean food pyramid
  - very top of the marine food chain
  - buoyant because of the oil contained in their over-sized livers
  - by no means the only pelagic animals under stress
* are capable of surviving on average six weeks without eating
  - carnivorous and eat fish, including other sharks
* are cartilaginous fish which move continuously in order to breath
  - cold-blooded fish and have a skeleton that is made of cartilage
  - common off Australia's beaches, but fatal attacks are rare
  - critical keystone predators that continue to maintain the balance of our fragile oceans
  - different from most other kinds of fish
  - difficult to control, but they can be hooked and subdued
  - dumb and they have been around for hundreds of millions of years
  - eaten as seafood in many areas, including Japan and Australia
  - elasmobranchs
  - especially vulnerable to overfishing because they mature slowly
* are extremely diverse in form, feeding habits, range of movement, and use of habitat
  - sensitive to even the slightest voltage
* are fairly intelligent, and have been compared to dogs or cats
  - have numerous senses to detect prey
  - fast swimmers
  - fierce predators, but they are very cautious
* are fish and, like other species of fish, use gills to breathe rather than lungs
  - because they have gills and get their oxygen from the water
* are fish that live in the water and are cold-blooded animals
  - throughout the world's oceans
  - fish, and virtually all fish breathe through the use of gills
  - food for the rich and the poor
  - formidable hunters, the top of the ocean's food chain
* are found all over the globe at different temperatures, and depths
  - in all seas
  - girthful, and use their width to drive forward with each body gyration
  - gnathostomes
  - good to eat
  - hard to kill
  - hatched or born as juveniles, or smaller versions of the adult
  - immune to practically every disease known to man
  - important apex predators in the marine environment
* are important to the health of the oceans
  - ocean's ecosystems and to both recreational and commercial fishermen
  - imune to every known sickness, including cancer
* are in danger of being overfished
  - extinction due to demand for their fins
  - inclined to bite when they smell blood
  - insects
  - interesting because they lived before the dinosaurs
  - internal fertilizers
  - key for a healthy reef
* are known as sharks
  - to live for many years
  - lighter than bony fishes because cartilage is lighter than bone tissue
* are located in bad movies
  - barrier reefs
  - business
  - coral reefs
  - museums
  - news
  - nightmares
  - novels
  - pacific oceans
  - pacifics
  - pet shops
  - poker games
  - restaurants
  - salt water
  - seawater
  - tanks
* are located in television programs
  - shows
  - zoos
  - loners
  - marine predators and that's the bottom line
  - mean, nasty creatures that eat people
  - misunderstood animals
  - more closely related to skates than to sea trout
* are more likely to attack a lone person
  - lone swimmer or individual surfer
  - multicellular organism
  - normally offshore, but have been caught close to the beach as well
  - notorious for beating a tarpon to a surface plug
  - omnivorous, which means they eat both meat and vegetation
* are one of the few sea creatures that practice internal fertilization and bear live pups
  - increasingly rare organisms seen on coral reefs
* are one of the most common species that are known to exist in almost all the Oceanic waters
  - feared sea animals
  - opportunistic when it comes to finding food
* are part of a family of fishes known as cartilage fishes
  - nature's recycling system
  - that nature
  - particularly sensitive to sounds of low frequency and have fine directional hearing
  - picky eaters
  - pre-historic and swam the oceans during the dinosaur era
  - predators of the marine world
  - predatory animals
* are present everywhere from the tropical seas to the polar region
  - in Hawaiian mythology
  - primarily marine, but a few species travel far up rivers
* are relatively rare creatures
  - rare, slow to breed, and take a long time to reach sexual maturity
  - remarkable at healing after injuries for instance
  - sensitive to light and can detect certain objects even in murky water
  - sexually dimorphic
  - slow and cumbersome
* are slow to mature and usually produce only very few young each time they breed
  - some of the most frequently studied cartilaginous fish
* are some of the oldest and most successful vertebrates on the earth
  - creatures on the planet
  - still so misunderstood as dangerous sea creatures
  - strong animals with very powerful jaws, some of which are capable of killing a human
* are the apex predators of the ocean
  - chief natural enemies of dolphins
  - greatest fish in the world, and the most invulnerable
  - main predators of the Australian sea lion
* are the most ferocious fish in the sea
  - successful predators in the ocean
  - oldest, smartest, and the most beautiful of all fish
* are the only fish that have cartilage instead of bones
  - eyelids, termed nictitating membranes
  - true stars
  - their main predators
  - top predators and keep levels of other marine life in check
  - trash fish
  - unable to see things clearly at a short distance
  - unique among living creatures in that they almost never get sick
  - unpredictable
  - usually very picky about what they eat
  - vertebrates without a bony skeleton
* are very good predators because of their excellent eyesight
  - numerous everywhere, especially the gigantic hammerheads and white-tipped sharks
  - powerful and beautiful creatures, and they are also very dangerous
* are very sensitive to low frequency sounds and have good directional hearing
  - the smell of blood
  - susceptible to over fishing due to their slow reproduction rate
  - well aware of their environment and appear to be fairly curious by nature
  - vicious man-hunters
  - voracious feeders on fish and other animals
* are well camoflaged to their surroundings
  - known to be highly suceptible to the stresses of capture and containment
  - wild animals, and deserve the same level of respect given to any other wild animal
  - wrongdoers
* belong to a group known as elasmobranchs
  - of fishes known as elasmobranchs
* belong to the cartilage fish subgroup
  - sea environment and they are on the top of the ecological food chain
* bite objects.
* breathe under water
  - using gills
* can Socialize
  - actually suffer from cancer
* can also detect sound with their lateral line system
  - feel vibrations in the water made by other fish
* can also sense electric and magnetic fields
  - electrical currents in the water indicating the presence of other fish
* can be difficult to study in their native environment
  - highly social, remaining in large schools
* can be six inches long and fully mature
  - yet fully matured
* can detect as little as one part per million of blood in the water from a mile away
  - blood and body fluids in very small concentrations
  - incredibly small electrical fields
  - tiny amounts of blood
  - follow just a few molecules of scent to it's source from miles away
  - have from five to seven gills
  - look like regular fish to the untrained eye
  - monitor vibrations in the water with a lateral-line system
  - mutate too
  - pump water over their gills by opening and closing their mouths
  - rapidly adapt to new environments when looking for food
  - secrete any extra salts through the rectal gland
* can see color, as indicated by the presence of cone cells in their retinas
  - well and they are very sensitive to movement
  - sense blood in the water as little as one part per million from a mile away
* can sense electrical impulses produced by animals
  - muscle movement in prey animals
  - shed many thousands of teeth throughout their lifetime
* can smell blood from a mile away
  - half a mile away
  - over a mile away
  - travel with great bursts of speed when excited
* catch fish
* chase fish
* close eyes
  - their eyes when they bite something
* come by the shore because most of their food is in that area
  - in a range of sizes
* come in all sizes, shapes, and colors
  - different colors and shapes
* conjure images of horror in many people's minds.
* conserve trimethylamine oxide and urea in blood.
* consider humans too bony and lean to make a good meal.
* continually loose their teeth
  - replace lost teeth
  - shed teeth as they grow
* desire eats.
* differ from most other fish in several ways
  - kinds of fish in a number of ways
* do attack humans from time to time, but the risk of attack is actually very slight.
* do get cancer even in their cartilage
  - cancer, even cancer of their cartilage
  - sick, but their incidence of disease is much lower than among the other fishes
* do have some bones, but it is limited to their spinal column
  - to deal with a slight influx of salt, which is excreted by a rectal gland
  - in fact get cancer
* dominate water.
  - everything
  - far less than most people imagine
  - lots of things, but fish and squid are in the diet of some species also
  - periodically depending upon their metabolism and the availability of food
  - sick, injured or weak fish because they're easier to catch
  - swimmers but ignore boats
  - tuna that eat mackerel that eat herring that eat copepods that eat diatoms
  - tuna, plankton, sardines, herring, small fish, and other sharks
* embody the spirits of long-dead but still fractious relatives.
* encounter divers.
* even possess a crude form of color vision.
* exhibit a great diversity in reproductive modes
  - all of the different kinds of reproduction
* exist in a wide range of sizes, shapes, colors, behaviors and abilities.
* face intense environmental pressure, and several species are now endangered.
  - stingrays, barbed tail notwithstanding
  - primarily on fishes, crabs, mollusks, seabirds and seals, etc
* figure prominently in Hawaiian mythology.
* generally attack in inshore waters, near deep channels or where rivers empty into the sea
  - have a small brain in comparison to their body weight
* get oxygen from the water through gills, as do other fish.
* give birth to offspring.
* go more by smell than sight
  - out to sea at the approach of a wave of cold weather
  - to the shore so they can see food they eat
  - relatively slowly and have low reproductive rates
* has-part backs
* hate to peel their food.
* have a bad reputation as being dangerous, fearless and unpredictable
  - blood salinity closer to freshwater than do salmon
* have a boneless skeleton made of cartilage that tough elastic substance
  - up of cartilage and a rounded body shaped like a torpedo
  - cartilage skeleton
  - continual growth of teeth so if one breaks it is immediately replaced
  - good sense of smell
  - habit of eating people
  - highly developed sense of smell
  - lot to fear from humans
  - lousy sense of smell
  - number of fleshy gill slits instead of a bony gill cover
  - remarkable sense of smell, to detect even minute amounts of blood in the water
  - resistance to cancer
  - set of teeth that stand up like our teeth do
  - skeleton made up of a tough, elastic substance called cartilage
  - slighter higher osmolarity than that of the sea water because they retain urea
  - special kind of scales called denticle
  - tendency to work together as a team
  - tongue referred to as a basihyal
  - total of six senses, five of which are involved in locating food
* have a unique and effective immune system
  - eye with a mirror behind the retina
* have a very keen sense of smell for blood
  - unique jaw structure, which makes their mouths especially effective weapons
  - amazing Adaptation capabilities
* have an electrical sense system for detecting prey
  - endoskeleton of cartilage alone and have no bones though they are vertebrates
  - excellent sense of smell and is how they are attracted to their prey
  - inner ear that is used to pick up acceleration and gravity in addition to sound
  - at least five rows of teeth
  - bones like other fishes
  - broad heads and oversized mouths evolved for eating
  - cartilage and have less bones
  - choices
  - crush teeth
  - denticles instead of scales
  - different-shaped teeth, depending on what they eat
  - electric sensory perception, from small sense organs in the pores of their nose
  - excellent eyesight and can see objects moving even in dim light
  - extremely well-developed sensory capabilities
  - feet and climbing equipment
  - fewer young at a time than most fish do
  - gill slits on each side of the head
  - to seven gill slits
  - gill slits rather than pores, and gill septa that help support gill filaments
  - gills on each side of their heads
* have good eyesight for being in the water, so they can see well during the day or the night
  - great sense of hearing
  - heterocercal tail in which the vertebral column extends up and into dorsal lobe of tail
* have highly developed sensors that can perceive even very weak electrical signals
  - sensitive eyes that can see extremely well in dim light
  - instinct
* have internal fertilization, and most give birth to live young
  - keen olfactory sense organs in the short duct between the front and back nasal openings
  - little commercial values
* have lots of rows of teeth
  - teeth - rows and rows
  - low blood pressure
  - lunate caudal fins
* have many gills slits on their necks
  - other interesting characteristics
  - rows of teeth, and if one is lost, another is available to replace it
  - uses to humans
  - multiple rows of teeth that are continually shed
* have no bones and are composed of cartilage
  - chest, and therefore they can be easily crashed on ground by their own weight
  - overlapping scales covering their bodies like other fish
  - nostrils
  - numerous rows of teeth attached at their bases by connective tissue
  - one of the keenest senses of smell of any animal
  - only a single type of heavy chain constant region, whereas humans have eight
  - peanut-sized brains and are incapable of learning
  - plenty
* have poor eyesight, but are good at sensing vibrations in the water
  - powerful immune systems and can resist many diseases, including cancer
  - relatively large brains, and can be compared to relatively advanced animals
  - sensory organs on their noses that detect movement
* have several means of sensing prey
  - sharp, triangle-shaped teeth
  - skeletons composed of cartilage rather than of bone
  - skin covered in millions of tiny teeth-like scales that point to the tail
  - super senses that can detect any prey from miles away
  - teeth for tearing meat, and breathe in water
* have the cartiliginous skeleton while the everyday guppie has bones
  - greatest sensitivity of any known marine animal to electric fields
* have the reputation of attacking human beings
  - the most fearsome creatures in the sea
  - same five senses as people
  - tough skin covered with rough modified scales, called dermal denticles
  - very sharp teeth and a good sense of smell and are very fast swimmers
* have what is known as a lateral line system
* help balance out the ecology in oceans.
* hunt fish
* include extinct sharks
  - great white sharks
  - horn sharks
  - zebra sharks
* includes brains
  - breasts
  - cell membranes
  - chest cavities
  - chests
  - corpi
  - cytoplasm
  - fish scales
  - fishbones
  - flippers
  - nuclei
  - pedal extremities
  - plasma membranes
  - rib cages
  - sections
  - skulls
  - sperm
  - sterna
  - vacuoles
  - vertebrate feet
  - yolks
* increase in backcountry and offshore.
* inhabit all the coastal waters and estuarine habitats of Australia's coast
* inspire awe even when observed through aquarium glass.
* is fish
* keep getting new teeth all their lives
  - growing their teeth throughout their lives
  - replacing their teeth all their lives
  - the ocean clean by eating dead or wounded fish
  - three swimmers in less than a year
* lack a swim bladder, so when they stop swimming they start to sink
  - airbladders that give bony fish buoyancy
  - the air bladder of bony fish to maintain buoyancy
  - true bone but instead have cartilaginous skeletons that are much lighter
* leap up out of placid waters.
* like flesh.
* like to follow the edge
  - hunt alone
* live all over the world, from warm, tropical lagoons to polar seas
  - over, from the cold polar waters to the warm tropical seas
* live in the sea although a few live in inland waters
  - and estuaries in Queensland but shark attacks are rare
  - only in warm water
* locate their prey by the low-frequency sounds emitted during swimming and other activities.
* lose teeth continuously throughout their lives.
* maintain a high level of urea in their blood and eyes
  - an internal environment which is hypertonic to seawater
  - neutral buoyancy by swimming constantly so that water can pump across their gills
* mature at a slow rate, leaving less time for it's species to reproduce
  - late in life, grow slowly, and produce few offspring
* navigate mainly by electro-reception and a sensitivity to pressure and water temperature.
* never attack without reason
  - stop growing new teeth
* normally avoid humans.
  - on many of Australia's beaches
* often employ complex hunting strategies to engage large prey animals
  - swim by the spot to feed on the abundant reef fish population
* open mouths.
* pass through all the previous stages to the eel or single nostril stage in their development.
* patrol the waters above and around the reef.
* perform an important role in the ecosystem, at the top of the oceanic food chain.
* play a key role as top predators.
* pose threats.
* possess a heterocercal caudal fin
  - superior immune system
* prefer fish
  - human blood
  - to attack lone victims
* prey most often on the weak members of a population
  - on loggerhead turtles throughout their lives
* produce slowly and produce few young.
* propagate by two's and four's, dozens at most.
* propel themselves using their tail fins.
* prowl the ocean depths and swim near sunny, sandy beaches.
* recover rapidly from severe injuries.
* reproduce at a very slow rate
  - internally
* reproduce sexually and eggs are fertilized internally
  - with internal fertilization
  - through internal fertilization and many shark species give birth to live young
* require a wire leader because of their sharp teeth
* roam oceans
  - meals
* seem to have a natural immunity to cancer.
* serve as an important part of the underwater community.
* share the top ocean predator spot with large squid, seals, dolphins and toothed whales
* shed their teeth a lot, and that's why there are so many fossil teeth around
  - throughout their lives, so fossil shark teeth are common in some places
* simply retain the fertilized eggs in the mother s body until they hatch.
* sink when they stop swimming.
* sometimes attack people, and sometimes it ends in death
  - misinterpret the movement of swimmers for that of a fish
* spend much of their time slowly cruising, keeping an eye out for a good meal.
* start schooling in Skeleton Bay.
* still live in the gulf water.
* stop growing when they reach puberty.
* swallow animals
  - their food whole or in big chunks
  - very fast and breath using gills
* tend to attack individuals
  - avoid the electric fields created by outboard motors
  - be seen quite often in cartoons whenever a scene involves the ocean
  - have active and inactive periods rather than sleep
  - prefer the shallower continental shelf areas
  - sink because they lack the buoyant swim blad- der of most bony fishes
* use electromagnetic impulses given off from fish thrashing in the water to find their prey
  - their tail to move through the water
* use three different methods of reproduction
  - primary methods to find their prey
* usually feed at night.
* vary greatly in size and habitat.
* visit coasts
* wander randomly through the ocean.
* wear some type of identifying equipment.
* yield more marketable products than any other single group of fishes.
+ Common misconceptions, Science, Biology: Society :: Lists :: Knowledge
  * Sharks can actually suffer from cancer. The myth that sharks do not get cancer was spread by the 1992 book 'Sharks don't get cancer' by I. William Lane. Extracts of shark cartilage was sold as cancer prevention treatments. Reports of carcinomas in sharks exist, and current data do not allow any speculation about the incidence of tumors in sharks.
+ Gill: Animal anatomy :: Anatomy of the respiratory system
  * Fish and frog gills are hidden on the sides of their heads. Sharks have many gills slits on their necks. Baby salamanders have gills that stick out like leaves from their heads.
+ Shark, Characteristics
  * Sharks have different-shaped teeth, depending on what they eat. For instance, some sharks have sharp, pointy teeth, while bottom dwelling sharks have cone-shaped teeth for crushing shells. Because there are so many different kinds of sharks, and because each kind has its own kind of special teeth, many people enjoy collecting shark teeth. First, they measure the length of the tooth in inches. Even more terrifying is that some of the 'Megalodon' teeth are 6 inches long so that suggets a shark 60 feet long.
  * Sharks have skin covered in millions of tiny teeth-like scales that point to the tail. If you rub along a shark towards the tail, it would feel smooth, but if you rub the other way, it would be rough. Sharks' teeth can be 20 times as big as human teeth and they can grow back if they are lost
  * Sharks are a common seafood in many places, including Japan and Australia. In the Australian state of Victoria, shark is the most commonly used fish in fish and chips, in which fillets are battered and deep-fried or crumbed and grilled. The soft bones can be easily chewed. They are considered a delicacy in coastal Tamil Nadu
  - Reproduction, Oviparity
  * Some sharks are oviparous, laying their eggs in the water. The egg has a yolk that feeds the embryo, very much like a chicken egg
  - Senses, Smell
+ Tonic immobility, Sharks: Zoology :: Ethology