Transcript Phylum Chordata - Shah`s Aquatic Science

Phylum Chordata
Vertebrates
Phylum Chordata
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Reproduction
 Amniote – vertebrates that have an amnion
 Anamniote - vertebrates that lack an amnion, or extraembryonic membrane
that surrounds the embryo and encases it in amniotic fluid
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All members of the phylum (the most advanced of the animal phylum) have a
stiffening notochord.
 Notochords are stiff rods of connective tissue.
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The also have a tubular dorsal nervous system and gill slits behind the oral
opening at sometime during their development.
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The notochord serves as a rigid support and a foundation for muscles and bone.
5% of 45,000 species of chordates lose their notochord as they develop.
 These are invertebrate chordates.
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95% retain the notochord or the vertebral column that forms around it.
 These are called Vertebrate Chordates.
Classification of Groups
Within the Phylum Chordata
 Phylum Chordata
 Subphylum Vertebrata:
 Class Agnatha (jawless fish) – Hagfish; lamprey
 Class Chondrichthyes (cartilage skeleton) – Sharks; Rays;
Skates
 Class Osteichthyes (bony skeleton) – tuna; seahorse;
puffers
 Class Amphibia – frogs; salamanders
 Class Reptilia – crocodiles; turtles; snakes
 Class Aves – gulls; penguins; terns
 Class Mammalia – Whales; seals
Fish
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Vertebrates
Live in water
Possess gills
Have fins
There are more species of fish and more individuals than species
and individuals of all other vertebrates combined.
Range in size form 10 millimeters to over 20 meters (.4 inches to
60 feet)
Weigh from 0.1 gram to 41,000 kilograms. (.004 ounces to 45
tons)
Ectotherms – cold blooded (can not maintain a steady internal
temperature)
40% of species live all or part of their life in freshwater.
60% live exclusively in salt water.
Class Agnatha
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(a = lacking; gnathos = jaw)
Examples – Hagfish and Lampreys
75 species
Characteristics
 Lack jaws
 No paired appendages/fins
 Have gill slits
 Have openings to slime glands
 Have round sucking mouths surrounded by organs sensitive to
touch
 Tails are flattened
 Eye are covered by thick skin
 Ectothermic
 anamniote
 Hagfish:
 Pink
 Live in colonies
 Feed on the inner tissues and
internal organs of its prey
 Lamprey;
 Have a toothed, funnel-shaped mouth
 Rasps through scales and skin to get nutrients from blood
Class Chondrichthyes
 (chondros = cartilage; ichthys = fish)
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True bones do not exists.
jaws with teeth
Anamniote
800 species
paired fins
Examples-Sharks and Rays
Tend to be larger than either Agnathans or bony fish.
Only a small fraction of all fish species are members of this group.
Nearly all are marine; a few species will inhabit estuaries and very few are
found in fresh water.
Skates have flattened bodies with spreading pectoral fins – They move by
flapping of these fins.
Rays:
 Some have a defensive barb on
their tail
 Some grow to 7 meters across
(giant Manta)
 Some have the ability to shock
their prey.
 smooth skin
 Do not have gas bladders, so
slightly negatively buoyant; they
sink if they stop swimming.
 flattened bodies with spreading
pectoral fins
 move by flapping of fins
Sharks:
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80% are less than 2 meters long
Not very intelligent
Hunt prey by vibrations in the water and
also by smell.
Do not have gas bladders, so slightly
negatively buoyant; they sink if they stop
swimming.
Covered with a tooth-like placoid scale.
Largest – Whale shark; 18 meters (60
feet), 41,000 kilograms (90,000 pounds);
feed on plankton
Carcharodon (Karcharos = sharp;
odontos = tooth) Great White Shark; 7
meters, 1,400 kilograms
Other “dangerous” species: Mako; Tiger;
Hammer head
Class Osteichthyes
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(osteum = bone; ichthys = fish)
27,000 + species
Anamniote
Paired fins
Success due to light, hard, strong skeleton that supports them.
Most numbers and successful of all vertebrates.
Representatives of this class are found in every marine habitat.
90% of all fish belong to the Class Osteichthyes and the Order Teleostei (teleos =
perfedt; osteon = bone)
 perch, tuna, flounder,etc.
a gas filled swim bladder to help maintain neutral buoyancy.
independently movable fins for well controlled swimming.
capable of great speed for pursuit or avoidance of predators.
effective camouflage.
social organization
orderly pattern of migration.
ability to cluster together in defensive schools.
Over 77 million tons of bony fish are taken annually form the ocean for
consumption.
Movement, Shape & Propulsion
 A fish’s resistance to movement (drag) is determined
by the frontal area, body contour and surface drag.
 Drag increases geometrically with increasing speed.
Faster swimming fish must be highly modified to
minimize drag.
 The most effective antidrag shape is a tapering
torpedo-like body plan.
 This shape produces minimum drag when they are:
 circular in cross-section
 greatest width is ¼ the length
 the point of max width occurs
about 2/5 the distance from the leading tip
 Thrust come from a combines effort of the body and
fins.
 Muscles in slender flexible fish (eels) create S-shaped
waves along the body. The body pushes against the
water.
 This movement is not efficient; body length to width
ratio must be too high (this increases the surface area
that creates drag)
 More efficient forms have shorter less flexible bodies
that undulate more rapidly and a hinged tail to transfer
muscular energy to the water.
 How Efficient?
 In the fastest fish 60-80% of muscle force delivered to the tail results in
forward movement.
 Marlin & swordfish can travel 33 meters/second (75 mph)
Maintenance of Level
 The density of a fish’s tissue is greater than surrounding water.
 This difference is offset by propulsive forces and by buoyant gas
or fat-filled bladders (swim bladder)
 The quantity of gas is controlled by:
 secretion and absorption of gas from the blood
 muscular contraction of the bladder.
 Fast predators lack a swim bladder. The volume would have
to change too rapidly and the chance of rupture is great.
Class Reptilia
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6200 species
amniote
Each of the 3 main groups within the Class Reptilia have marine
representatives:
 turtles
 sea snakes
 marine lizards
Each of these groups:
 are ectothermic
 breathe air using lungs
 are covered with scales and an impermeable skin
 have salt glands that concentrate and excrete salt
Marine Turtles
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Most successful living marine reptile
8 Species
More streamlined
Shell lacks enough internal space for head and limbs
Forelimbs are modified as flippers
Hind limbs act as rudders
Most abundant and wide spread are the 2 species of
green sea turtles
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The largest of the turtles is the Atlantic Leatherback
Have a skin covering the shell
Reach 2 meters in length
Weigh more than 6oo kilograms (1300 pounds)
 All marine turtles are in danger of extinction:
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breeding beaches are being developed
Their eggs and shells are in demand
They drown in fishing nets
Feeding areas are polluted
Floating plastic bags are mistaken for food and eaten
Marine Crocodiles
 One living species
 Lives in mangrove swamps and isolated mainland shores in the
tropical western Pacific
 Very aggressive and hunts in packs
 7 meters long
 Weighs over 2.000 pounds
Marine Lizards
 One surviving species – Galapagos Marine Iguana.
 Live among the intertidal rocks and beaches of the
Galapagos Islands
 Grow to more than 1 meter in length
 Weigh 9 kilograms (20 pounds)
 Swim by undulating body and tail
 Live in colonies and feed on off-shore seaweeds.
Sea Snakes
 50 species of sea snakes
 Most are native to the Indian Ocean and the western
Pacific areas
 There are none in the Atlantic
 They hunt among the coral heads
 Sea snakes must return to the surface to breathe
 The young are born alive in the water
 Venom is among the most powerful animal poison
known.
 Prey is held in the mouth until saliva which contains the
neurotoxin enters wounds and takes effect.
Class Aves
 Marine birds:
are endotherms – they generate and regulate metabolic heat
have thin hollow bones without fatty insulation
have light weight beak replacing jaws and teeth
4 chambered heart to circulate blood under high pressure
have a respiratory system that can accept large quantities of
oxygen
 all birds lay eggs on land
 8800 species
 amniotes
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 Only 3% of known birds are classified as sea birds.
 Sea birds have salt secreting glands in their head like
marine reptiles.
 Groups of sea birds:
 Tubenoses
 100 species – world’s most oceanic birds;
examples – albatrosses, petrels and shear waters
 Albatross
 Wingspan of 12 feet
 Weighs 22 pounds
 Wings are aerodynamic; can soar at high
speeds using very little energy
 Pelicans
 This group includes pelicans, cormorants, frigate
birds, and Boobies
 All have throat patches
 All have webbed feet
 They do not spend much time over open ocean
 The frigate can not walk or swim; its skeleton
weighs less than its feathers
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Penguins
 Have lost the ability to fly
 Excellent swimmers
 Have fatty insulation making feathers greasy
 Neutrally buoyant; can dive to depths of 875 feet and stay submerged for
10 minutes
Class Mammalia
 4500 species
 amniote
 3 Living groups
 Cetacea – Porpoises, dolphins, and whales
 Carnivora – seals, sea lions, walruses and sea otters
 Sirenia – manatees and dugongs
 All exhibit mammalian characteristics:
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endothermic
breathe air
give birth to living young
young suckle milk produced in mammary glands
have hair at some time during life
 All marine mammals have 4 common features:
 Streamlined body shape with limbs adapted for swimming
(drag is reduced by a slippery skin or hair covering)
 They generate internal body heat through high metabolic rate
and conserve the heat by layers of insulation (fat or fur)
 A respiratory system modified to collect and retain large
amounts of oxygen.
 Many osmotic adaptations allow marine mammals to do away
with the need for fresh water.
Order Cetacea (whales)
 90+ species
 Range in size from 6 feet to 110 feet
 Can weigh up to 110 tons
 Suborder Odontoceti (toothed whales)
 Have teeth and are active predators
 Have a high brain weight to body weight ratio
 Use echolocation (biological answer to sonar) to find prey
 Suborder Mysticeti
 Baleen whales – have no teeth; filter
feeders
 (blue whales, humpback, and grey whales)
Order Carnivora
 Suborder Pinnipedia (seals, sea lions, and walruses)
 True seals – smooth head, no external ears
 Elephant seals have diving record of 5,120 feet.
Order Sirenia
 Bulky, small brained manatees and dugongs
 Herbivores 15 feet; 1500 pounds