Biology Presentation

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Biology Presentation

• Fish
• ---Sharks---

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Fish

• Fish are divided into two groups.
• Chondrichthyes
• E.g. sharks, rays
• Osteichthyes
• E.g. common fish

A Ray
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Sharks - Classification

• Kingdom Animalia
• Phylum Chordata
• Class Chondrichthyes
• Orders total 8
• Families total 35
• Species Nearly 500

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Shark Attack!!!!
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Sharks

• More than 80 are harmless
• Varying sizes
• shortest is 15cm at maturity
• longest is 14m
• average shark is about 90cm
• All are carnivores
• All marine

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Morphology 1

• No external ear
• Tail is asymmetrical

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Morphology 2

• Have gill openings as series of slits

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Morphology 3

• a fleshy pair of pectoral fins, pelvic fins,anal
  fins and one or two pairs of dorsal fins

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Morphology 4

• Thick skin with tooth-like placoid scales
• Used by carpenters as sandpaper in the past

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Morphology 5

• Males have a pair of pelvic claspers

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Male
Female
Male
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Teeth

• Made of cartilage
• Triangular in shape and razor sharp
• Many rows
• May have up to 3000 teeth in 6 20 rows
• As those in front wear down, others move forward
  from behind
• Usually only the first 2 rows are used

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Shark Attack

• Sharks are generally timid and cautious
• Only some species poses potential threat, like
  Great White (Charcharodon carcharias),hammerhead
  shark (sphyrna)
• Chances of being killed by sharks is much lower
  than that of dieing in a car accident on the way
  to the beach

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Why do Sharks attack Human?

• Mistake human for food
• Looks like seals or big fish
• due to poor visibility and turbulent water
  movements
• Attracted to movements of swimmers blood or fish
  bait behind boats flashes of watches
• Take a bite, realise its mistake, go away

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Conservation of Sharks

• World population of sharks are constantly
  decreasing
• Mainly due to overfishing and bycatch
• Catches sharks for fins and flesh
• Sharks get tangled on longlines set up to catch
  other fish

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This sharks fins were cut off at sea. It was
then throw back into the ocean to suffer its long
and painful death on the ocean floor.
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Conservation cont

• Moreover, sharks cannot reproduce quickly
• Long gestation period
• Av. 9-12 months, longest 22 months
• Female sharks rest a year or two between
  pregnancies
• Have to control killing of sharks before their
  population becomes too low

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Comparison of Chondrichthyes Osteichthyes
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Similarities

• Are poikilotherms
• No external ear
• Have a pair of pelvic fins and a pair of pectoral
  fins

A bullshark
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Differences
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Differences 2
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The End Thank You!