Transcript Deuterostomes

Deuterostomes
(coelomates = second mouth)
Phylum Echinodermata
• Sea stars
• Sea cucmbers
• brittle stars
• Sea urchins
• Sand dollars
• Feather stars
Echinoderm Ancestral Traits
• Coelom
• Bilaterally symmetrical larvae
– But all adults have radial symmetry
• Complete digestive system
– (alimentary canal)
Retro traits : bringing back the past
• Regeneration ability
• Radial symmetry: works great for sessile
– Seems to work for slow moving creatures too
– Only larvae still bilateral (evidence of a
bilateral ancestor)
• No head or brain
– Sensory receptors and nerves spread out in a
network around the body
• No respiratory, circulatory or excretory
system
– Diffusion through tube feet
Echinoderm Derived Traits
• Endoskeleton of hard spiny plates
– Covered by thin layer of epidermis
• Tube feet (100s of suction cup feet)
Sea Star Feeding
• Sea star pulls a
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•
bivalve open using its
tube feet
Sea star everts its
stomach into the
bivalve shell and
digests the meat
inside
Stomach returns to
interior of sea star
Phylum Chordata
• All are deuterostome coelomates
• All have bilateral symmetry at some stage
of their life
4 key Chordate Characteristics
• Dorsal hollow nerve cord
• A notochord (skeletal rod) supports the
nerve cord at some point in development
• Pharyngeal pouches at some point
• Post anal tail at some point
Phylum Chordata has 3 subphyla
1) Subphylum Urochordata – tunicates (sea squirt)
2) Subphylum Cephalochrodata – lancelets
3) Subphylum Craniata –
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Superclass : Agnatha – jawless fish
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2 extant classes: hagfish & lamprey
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Superclass: Gnathostomata – jaw mouth
classes: chondrichthyes, osteichthyes,
Amphibia, Reptilia, Aves, Mammalia
Tunicates- Subphylum Urochordata
• Only larvae have chordate characteristics
•
and muscle segments called myomeres
• Adults sessile filter feeders
Tunicates = sea squirts
Subphylum Cephalochordata
• Lancelets
• Tiny filter feeders
• Segmented muscles called
• Myomeres
• ‘Head chord’ notochord extends far forward
Subphylum Craniata
• All have cartilagenous /bone endoskeleton
•
• Covers at least the brain (Craniata)
• Most have vertebrae to protect the dorsal
nerve cord
•
(only the hagfish do not)
Primitive Craniates= Superclass
• (jawless fish) Agnatha
• Hagfish
• Lampreys
• Ostracoderms
– (extinct silurian fish)
– Armor plated
Superclass Gnathostomata
• Jaw mouth = all have jaws
• Jaws evolved from gill arches
• Advantage: break shells/armor/exoskeletons,
bite off pieces
• Includes All other fish
•
(not hagfish or lamprey)
• All tetrapods (gnathostomes that have limbs)
Class Chondrichthyes
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Cartilagenous Fish
Sharks
Skates
Rays
• Traits
– No swim bladder
– No operculum (must swim to breath)
Class Osteichthyes – bony fish
• Have bone skeleton
• Most have swim bladder
• Have operculum over gills
Counter current exchange in gills
• Closed circulatory system
• Low O2 blood near lowest O2 water
• Maintains concentrations gradient
Lobe-finned fish developed supportive
fins & simple lungs from swim bladder
Class Amphibia = first Vert. on land
• Eggs & larvae in water
• Larval respiration gills/skin
• Larval circulatory system like
a fish
• 2 chambered heart
• single loop circulatory system
Adults move onto land
• Stronger skeletal system (no buoyancy)
• Respiration by lungs/skin
• New type of circulatory system
– 3 chamber heart
– 2 loop circulatory system
– Faster, more efficient
• Evolutionary Advantage to land
– No predators
– Insects for food
Class Reptilia
• Amniote egg = freedom from water
• Extraembryonic membranes amnion, chorion
• Shelled egg = internal fertilization
• Scales = prevent dehydration
• no O2 from diffusion any longer
• Lungs developed folds and pouches
– Increased surface area
• Heart begins to divide into 4 chambers in
crocodilians
Class Aves = Birds
• Amniote eggs
• Feathers & scales
• Flight: light bones, flight feathers,
• Endothermic: high metabolism=high energy
• Lungs with air pockets – always fresh air
• 4 chambered heart – no mixing of oxygenated
and un-oxygenated blood
Counter current exchange in lung
Class Mammalia
• Fur/hair & subcutaneous fat
• Endothermic
• Produce milk (mammary glands)
• All have amniotic membrane but not all are
contained in an egg
Mammal Amniotes
• Amniotes of 3 types
– Monotremes lay eggs
– Marsupials babies are born as immature
embryos and finish development in pouch
– Placental mammals embryos obtain nutrients
from their mother through a placenta.
Offspring are much more mature when born
Amnion
membranes
Amniote shared derived traits
• Dry skin prevents water loss
• Improved Lung & ventilating rib cage
• Legs elevate body
• Kidney remove waste while conserving H2O
• Internal fertilization
• Amnionic egg with 4 membranes + shell
– Keeps egg moist but allows gas exchange
– Some mammals no longer have shelled egg
Amniotes diverged quickly
• 1) synapsids evolved into therapsids and
then into mammals
• 2) Sauropsids evolved into Diapsids which
then branched into reptiles, dinosaurs and
birds