SHARKS
SHARKS
Kingdom Animalia
Phylum Chordata
Subphylum Vertebrata
Class Chondrichthyes
8 Orders
30 Families
~350 Species
SHARKS
• first appeared ~ 450 my ago
SHARKS
Iniopteryx
~375 my
Belantsea
~350 my
Helicoprion
~345 my
Ischyodus
Stethacantus
~150 my
~375 my
SHARKS
• first appeared ~ 450 my ago
• “modern” forms ~ 300 my
• many early forms became extinct w/
dinosaurs; others evolved
coincident w/ rise of mammals
(white shark 60-65my)
• Carcharodon megalodon 50-35 my –
teeth 10in; length 40’
SHARKS
Of ~ 350 extant species:
• 82% 4 m
angel sharks
sawtooth sharks
dogfish sharks
cow sharks
Family Carcharhinidae
(Requiem) – 48 species:
tiger, blue, bull , reef
Family Lamnidae –
(mackeral) white, mako,
sand tiger, basking
whale shark, nurse
hammerhead, bullhead
SHARKS
Shark senses:
• eyes – similar to most vertebrates, size
varies w/ habitat; retinas more rod
cells (dim light), fewer cone cells
(bright light); tapetum (tapetal
plates); nictitating membranes
• ears – great accoustic sensitivity;
sharks: 10-800Hz (struggling fish),
humans: 25-1600Hz
• lateral lines - >6,000 pits, grooves, canals
lined w/ cilia – sensitive to low freq.
pressure waves
• nasal sacs – some sharks 80% of brain
devoted to smell
• Ampuli of Lorenzini
• teeth
SHARKS Great White
Sand tiger
placoids (dermal denticles)
Tiger
SHARKS
Sharks may shed as many as 30,000 teeth in
a lifetime!
SHARKS
Why do sharks attack humans?
• mistaken identity?
SHARKS
Why do sharks attack humans?
• mistaken identity?
• test bites?
• territoriality?
• hungry?
SHARKS
Some shark factoids:
• more humans are killed by dogs in the US
each year than have been killed by
sharks in US waters in the last 100
years
• 20 Great White sharks die in fishing nets off
CA each year; 0.13 humans are killed by
Great Whites
• more people are killed by hogs in Indiana
than by sharks in the US
• worldwide, about 3 times as many people
are killed by elephants than sharks
• You are: 6,527X more likely to die on the
highway, 235X more likely to be killed
by lightning, 37.5X more likely to die by
snake bite than being killed by a shark
SHARKS
Some shark factoids:
• You are more likely to be killed by a falling
TV than being killed by a shark
• You are 130X more likely to be killed by a
deer than by sharks
• More people are killed each year by electric
toasters than by sharks
• More people die by being buried in beach
sand each year than are killed by sharks
• 6X more people are killed by ATV accidents
in the US each year (600) than have ever
been killed by sharks in all of US history
• More people are seriously injured in ATV
accidents each year (125,000) than have
ever been injured by sharks worldwide in
recorded history
SHARKS
Humans kill more than 100,000,000 sharks
per year, many just for their fins
So who is the more dangerous predator?