ap biology vertebrate evolution
TRANSCRIPT
Vertebrates Evolution
Phylum Chordata• Vertebrates are a subphylum
of the phylum Chordata• This lecture will build up to
vertebrates and mammals by moving through the Chordata Phylum, from the most inclusive traits and simpliest organisms to the to most specific traits and complex organisms
Phylum Chordata
• This phylum includes– All vertebrates– Urochordata
(tunicates)– Cephalochordata
(lancelets)– Myxini (hagfish)
Characteristics of Chordates Many appear only during embryonic
development1. Notochord - Chordates named for
this structure; a long flexible rod that appears during embryonic development (some adults retain it)
• Provides skeletal support• Most adults retain only a
remnant of this• In humans it becomes the
gelatinous disks between our vertebrae
Characteristics of Chordates Many appear only during embryonic
development
2. A dorsal, hollow nerve cord - forms from a plate of ectoderm that rolls into a hollow tube; develops into the central nervous system
Characteristics of Chordates Many appear only during embryonic
development3. Pharyngeal clefts -
grooves that separate a series of pouches along the sides of the pharynx.
• Usually develop into slits that allow water to enter and exit the mouth without going through the digestive tract
• Become gill slits in fish or become part of the ear in terrestrial animals
Characteristics of Chordates Many appear only during embryonic
development
4. A muscular tail posterior to the anusMany adults lose this during embryonic
development
Invertebrate Chordates
• 2 subphyla - Urochordata (tunicates) and Cephalochordata (lancelets)
• Think of these 2 groups as simpler versions of vertebrates
• Tunicates - most primitive; like other chordates during larval stage, lose chordate traits as adults
Craniates• Chordates that have a
head• Most ancient of these
are the hagfish• Hagfish are marine,
bottom dwelling scavengers
• No vertebrae• Do have a skull made
of cartilage
Vertebrates
• Craniates with a backbone
• Evolved during the Cambrian when some Craniates developed
• more complex nervous systems
• more complex skeletons
• more extensive skull
• backbone composed of vertebrae that encloses the spinal cord
Vertebrates
• Lampreys are the oldest line of vertebrates
• Marine or freshwater• Cartilage pipe surrounds
the notochord• No jaws - have a rasping
mouth that bores holes in the sides of fish - live on the blood of their host
Gnathostomes
• Vertebrates with jaws– Evolved from the
pharyngeal slits– 2 major classes:
• Class Chondrichtyes
• Class Osteichthyes
Gnathostomes - Class Chrondrichythyans• Sharks, rays, and their relatives• Flexible endoskeletons made of
cartilage• Streamlined bodies• Will sink if they stop swimming
because they are denser than water
• Have changed little over 300 million years of evolution
Shark Reproduction• Eggs fertilized internally• Some are oviparous - lay
eggs that hatch outside the body
• Some are ovoviviparous - fertilized eggs stay in body, hatch in uterus
• Some are viviparous - baby develops inside the uterus and gets nutrients there
Horn shark egg case
Gnathostomes - Class Osteichthyes
• The bony fishes• Most numerous of all the
vertebrate groups• 2 main classes
– The ray-finned fish– The lobe fin fish
• Includes lungfish - freshwater, air gulpers
• Have an ossified (bony) endoskeleton
• Covered in scales• Have a swim bladder - air sac
that controls buoyancy
Most fish ray finned
Tetrapods - Gnathostomes
with limbs & feet• Evolution of limbs and
feet from fins ~ 360 mya
• Loss of gill slits• Fusion of pelvic bones
to backbone• All of these adaptations
lost or altered in various groups of tetrapods
Tetrapods - Class Amphibia• Includes salamanders, frogs, and caecilians• Still closely tied to water• Rely on skin for gas exchange with environment• Not all have legs• Some have an aquatic larval stage with a terrestrial adult
life• Eggs do not have a shell• External fertilization• Complex social behavior
Tetrapods - Amniotes
• Tetrapods with a terrestrial adapted, amniotic egg
• Consists of mammals and reptiles (including birds)
Tetrapods - Amniotes• Evolution of the amniotic egg very important for life on land
– Shell retains water– Now animals can live away from water– Amniotic eggs have an extramembryonic membrane that functions in
gas exchange, waste disposal, and transport of nutrients to embryo
Tetrapods - Reptiles• Have scales that contain
keratin– No longer breath through skin
like amphibians• Get oxygen through lungs• Lay eggs on land• Internal fertilization• Most are ectothermic -
control body temp with behavior, not metabolism
Tetrapods - Reptiles• Extinct reptiles include:
– Dinosaurs (land dwelling)– Pterosaurs (flying)– Plesiosaurs (marine)
• Modern reptiles include:– Turtles– Tuataras– Lizards– Snakes– Alligators– Crocodiles
tuatara
brown basilisk
Giant Galapagos
Tetrapods - Birds• Lay amniotic eggs (like reptiles)• Have keratin containing scales on
their legs (like reptiles)• Endotherms - maintain a warm
internal body temp • 4-chambered heart• High metabolism• Larger brains than reptiles
Tetrapods - Birds
• Most have bodies adapted for flights– Light, hollow bones– Relatively few organs– Wings– Feathers
Amniotes - Mammals
• Amniotes that have hair and produce milk from mammary glands
• Endothermic • Most born, not hatched• All have internal
fertilization• Large brains• Teeth
Mammals• 3 groups:
– Monotremes - egg laying, have hair, produce milk, playpuses, spiny anteaters
– Marsupials - give birth to embryo, completes development in a pouch while nursing, wombats, kangaroos, Tasmanian devils
– Placental mammals (eutherians) - longer pregnancy, deer, mice, tigers, primates
Mammals - primates• All have
– hands & feet that grasp– Large brains– Short jaws– Forward-looking eyes– Flat nails– Well-developed parental care– Complex social behavior
Mammals - primates• 3 subgroups
– Lemurs, lorisese, pottos
– Tarsiers– Anthropoids
(monkeys, apes, humans) lemurs
tarsier
ape
Mammals - humans • Increase brain volume• Shorter jaw• Less of a size difference between the
sexes• Different family structures
Jane Goodall
Diane Fossey
Quick CheckFor each new clade,
list the primary feature that separates it from
the clade before it.