chordates have a notochord and a dorsal, hollow nerve cord
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Chordates have a notochord and a dorsal, hollow nerve cord. Vertebrates are a subphylum of phylum Chordata Chordates are bilaterian animals that belong to the clade of animals known as Deuterostomia - PowerPoint PPT PresentationTRANSCRIPT
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Chordates have a notochord and a dorsal, hollow nerve cord
• Vertebrates are a subphylum of phylum Chordata
• Chordates are bilaterian animals that belong to the clade of animals known as Deuterostomia
• Two groups of invertebrate deuterostomes, the urochordates and cephalochordates, are more closely related to vertebrates than to invertebrates
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Derived Characters of Chordates
• All chordates share a set of derived characters
• Some species have some of these traits only during embryonic development
• Four key characters of chordates:
– Notochord
– Dorsal, hollow nerve cord
– Pharyngeal slits or clefts
– Muscular, post-anal tail
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Pharyngealslits or clefts
Mouth
Brain
Dorsal,hollow
nerve cord
Notochord
Musclesegments
Muscular,post-anal tail
Anus
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Notochord
• The notochord is a longitudinal, flexible rod between the digestive tube and nerve cord
• It provides skeletal support throughout most of the length of a chordate
• In most vertebrates, a more complex, jointed skeleton develops, and the adult retains only remnants of the embryonic notochord
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Dorsal, Hollow Nerve Cord
• The nerve cord of a chordate embryo develops from a plate of ectoderm that rolls into a tube dorsal to the notochord
• The nerve cord develops into the central nervous system: the brain and the spinal cord
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Pharyngeal Slits or Clefts
• In most chordates, grooves in the pharynx called pharyngeal clefts develop into slits that open to the outside of the body
• Functions of pharyngeal slits:
– Suspension-feeding structures in many invertebrate chordates
– Gas exchange in aquatic vertebrates
– Develop into parts of the ear, head, and neck in terrestrial vertebrates
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Muscular, Post-Anal Tail
• Chordates have a tail posterior to the anus
• In many species, the tail is lost during embryonic development
• The tail contains skeletal elements and muscles
• It provides propelling force in many aquatic species
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Vertebrate Classes
• Kingdom Animalia
– Phylum Chordata
• Sub-phylum Vertebrata
– Class Agnatha
– Class Chondrichthyes
– Class Osteichthyes
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Class Agnatha (Lampreys and Hagfish)
• Lampreys and Hagfish represent the oldest living lineage of vertebrates
• They are jawless vertebrates inhabiting various marine and freshwater habitats
• They have cartilaginous segments surrounding the notochord and arching partly over the nerve cord
• No scales or paired fins
• No gill coverings
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Slime glands
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Chondrichthyans (Sharks, Rays, and Their Relatives)
• Members of class Chondrichthyes have a skeleton composed primarily of cartilage
• The cartilaginous skeleton evolved secondarily from an ancestral mineralized skeleton
• The largest and most diverse subclass of Chondrichthyes includes the sharks, skates, and rays
• No gill coverings
• Scales
• Lateral line system
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Blacktip reef shark (Carcharhinus melanopterus).
Pectoral fins Pelvic fins
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Ray-Finned Fishes and Lobe-Fins
• The vast majority of vertebrates belong to a group called Osteichthyes
• Nearly all living osteichthyans have a bony endoskeleton
• Aquatic osteichthyans are the vertebrates we informally call fishes
• Fishes control their buoyancy with an air sac known as a swim bladder
• Fishes breathe by drawing water over gills in chambers covered by a bony flap called the operculum
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Nostril
BrainSpinal cord
Swimbladder
Dorsal fin Adipose fin(characteristicof trout)
Caudal fin
Anal fin
Intestine
GonadPelvicfin
Urinarybladder
AnusLateralline
Cut edgeof operculum
Gills
KidneyHeart
Liver
Stomach
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Ray-Finned Fishes
• Class Actinopterygii, the ray-finned fishes, includes nearly all the familiar aquatic osteichthyans
• The fins, supported mainly by long, flexible rays, are modified for maneuvering, defense, and other functions
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Clownfish
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Lobe-Fins
• The lobe-fins, class Sarcopterygii, have muscular and pectoral fins
• They include coelacanths, lungfishes, and tetrapods
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Tetrapods are gnathostomes that have limbs and feet
• One of the most significant events in vertebrate history was when the fins of some lobe-fins evolved into the limbs and feet of tetrapods
• Tetrapods have some specific adaptations:
– Four limbs and feet with digits
– Ears for detecting airborne sounds
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Amphibians
• Most amphibians have moist skin that complements the lungs in gas exchange
• Amphibian means “two lives,” referring to the metamorphosis of an aquatic larva into a terrestrial adult
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• Order Urodela includes salamanders, which have tails
• Order Anura includes frogs and toads, which lack tails
• Order Apoda includes caecilians, which are legless and resemble worms
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Order Urodela. Urodeles (salamanders)retain their tail as adults.
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Order Anura. Anurans, such as this poisonarrow frog, lack a tail as adults.
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Order Apoda. Apodans, or caecilians,are legless, mainly burrowing amphibians.
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The male grasps the female, stimulating her to release eggs. The eggs are laid and fertilized in water. They have a jelly coat but lack a shell and would desiccate in air.
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Amniotes are tetrapods thathave a terrestrially adapted egg
• Amniotes are a group of tetrapods whose living members are the reptiles, including birds, and the mammals
• Amniotes are named for the major derived character of the clade, the amniotic egg, which contains membranes that protect the embryo
• The extraembryonic membranes have various functions
• Amniotes have other terrestrial adaptations, such as relatively impermeable skin and the ability to use the rib cage to ventilate the lungs
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Extraembryonic membranes
Shell
Embryo
AllantoisAmnion
Amniotic cavitywith amniotic fluid
Chorion Yolk sac
Yolk (nutrients)
Albumen
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Reptiles
• The reptile clade includes the tuatara, lizards, snakes, turtles, crocodilians, birds, and the extinct dinosaurs
• Reptiles have scales that create a waterproof barrier
• They lay shelled eggs on land
• Most reptiles are ectothermic, absorbing external heat as the main source of body heat
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Turtles
• Turtles are the most distinctive group of reptiles alive today
• All turtles have a boxlike shell made of upper and lower shields that are fused to the vertebrae, clavicles, and ribs
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Eastern box turtle (Terrapene carolina carolina)
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Alligators and Crocodiles
• Crocodilians belong to an archosaur lineage that dates back to the late Triassic
American alligator (Alligator mississipiensis)
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Birds
• Birds are archosaurs, but almost every feature of their reptilian anatomy has undergone modification in their adaptation to flight
• Birds are endothermic, capable of keeping the body warm through metabolism
• Many characters of birds are adaptations that facilitate flight
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Bone structure
Feather structure
Wing
ForearmWrist
Finger 1
ShaftShaftBarb
Palm
Finger 2
Finger 3
Barbule
Hook
Vane
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Mammals are amniotes that have hair and produce milk
• Mammary glands, which produce milk, are a distinctively mammalian character
• Hair is another mammalian characteristic
• Mammals generally have a larger brain than other vertebrates of equivalent size
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• Monotremes are a small group of egg-laying mammals consisting of echidnas and the platypus
• Marsupials include opossums, kangaroos, and koalas
• A marsupial is born very early in its development
• It completes its embryonic development while nursing in a maternal pouch called a marsupium
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Short-beaked echidna (Tachyglossus aculeatus),an Australian monotreme. Monotremes have hairand produce milk, but they lack nipples. Monotremes are the onlymammals that lay eggs (inset).
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A young brushtail possum. The young of marsupials are born very early in their development. They finish their growth while nursing from a nipple (in their mother’s pouch in most species).
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Marsupial mole
Plantigale
Wombat
Sugar glider
Marsupial mammals Eutherian mammals
Tasmanian devil
Kangaroo
Mole
Deer mouse
Woodchuck
Flying squirrel
Wolverine
Patagonian cavy
In Australia, convergent evolution has resulted in a diversity of marsupials that resemble eutherians in other parts of the world
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Eutherians (Placental Mammals)
• Compared with marsupials, eutherians have a longer period of pregnancy
• Young eutherians complete their embryonic development within a uterus, joined to the mother by the placenta
• The mammalian order Primates includes lemurs, tarsiers, monkeys, and apes
• Humans are members of the ape group
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Derived Characters of Primates
• Most primates have hands and feet adapted for grasping
• Other derived characters of primates:
– A large brain and short jaws
– Forward-looking eyes close together on the face, providing depth perception
– Well-developed parental care and complex social behavior
– A fully opposable thumb