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Classical animal phylogeny: based on coelom
chordates
echinoderms
arthropods
tardigrades
annelids
mollusks
Echinoderms and Chordates
Deuterostomes
Protostomes
Coelomate animals
rotifers
Pseudocoelomate animals
roundworms
Readings:
Chapter 25, pp 414-415; pp 418-435
flatworms
Acoelomate animals
Animals with a 3-layer embryo
cnidarians
Animals with tissues
sponges
placozoans
Animals
Fig. 25-7a, p. 407
Alternative: Phylogeny based on DNA and proteins Deuterostomes
chordates
echinoderms
arthropods
tardigrades
Neither tree considers “advanced” characteristics
•  Sociality
Ecdysozoa
roundworms
–  Present in insects & vertebrates
Protostomes
rotifers
•  Complex behaviour
mollusks Lophotrochozoa
annelids
flatworms
•  Lifestyle: active or sessile
–  Present in insects & vertebrates
–  Both occur in echinoderms, molluscs
Animals with a 3-layer embryo
cnidarians
sponges
placozoans
Animals with tissues
Animals
Fig. 25-7b, p. 407
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Characteristics of Echinodermata
Phylum: Echinodermata
•  Tube feet
•
•
•
•
•  Spicules, spines, or plates
Entirely marine
Invertebrate
Deuterostomes
±10,000species
•  made of calcium carbonate •  (echinoderm means spiny skin).
–  Sea stars
•  “Starfish”
–
–
–
–
upper
stomach
Sea urchins
Brittle stars
Sand dollars
Sea cucumbers
•  Major marine predators
anus
gonad
ossicle (stiffening,
support structure)
spine
lower
stomach
–  Eat mollusks, other animals
coelom
•  Regenerative capacity
digestive gland
–  Sea stars can regenerate entire ‘arms’
eyespot
spine
•  Symmetry
–  Pentaradial in adults
–  Bilateral in larvae
•
•
•
•
•
ossicle
Summarizing Echinoderms
Phylum Echinodermata:
Sea Urchins
Sand dollars
etc
Browsers
–  Major players in marine ecosystems
–  Can be extremely damaging to kelp forests and to coral reefs • Symmetry
–  Bilateral in larvae
–  Pentaradial in adults
•  Uncephalized
– Neural net; no brain
Deuterostomes (like vertebrates)
Uncephalized
Unsegmented
Relationship to other phyla
•  Name means “spiny skin”
•  Characteristics
–  Spicules in skin
–  Internal skeleton •  made of calcium carbonate
–  Tube-feet
–  Unclear
–  Derive from bilaterally
symmetrical animals
•  Characteristics
–  Note outer defensive spicules
–  Walk on tube feet
•  Major model system –  fertilization, embryogenesis, and development –  Genome of one species of sea urchin has been sequenced.
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Phylum Chordata: Classification
Phylum Chordata
•  Classes: Vertebrata
•  Major subphyla
•
•  Vertebrates
–  Urochordata or
Tunicates
–  Cephalochordata or
Lancelets
–  Vertebrata or vertebrates
–  Agnatha
–  Placodermi
–  Chondrichthyes
–  Osteichthyes
–  Amphibia
–  Reptilia
–  Aves
–  Mammalia
•  Minor subphylum
–  Xenoturbella
»  Prototheria or
monotremes
»  Metatheria or
marsupials
»  Eutheria or
placental mammals
Defining characteristics
(May be present only in larval stages)
1.  Notochord
2.  Tubular dorsal nerve cord
(contrast with ventral nerve cord of annelids)
3.  Pharynx
1.  Muscular tube derived from mesoderm
2.  Functions in feeding and/or respiration
3.  Not homologous with pharynx of protostomes
(note this in idssecting the earthworm)
4.  Wall of pharynx contains gill slits
5.  Tail extending beyond anus
Subphylum: Urochordata, Class Tunicates
Larva
•  Named for tough outer layer or tunic. •  Examples: Sea squirts –
–
–
–
Squirt filtered water out of a siphon
Basic chordate features in larvae
Sessile as adults Retain only the filter-feeding pharynx
•  Note -- this pharynx is not homologous
to that of planaria or cephalopods, but
analogous.
atrial opening
(water that passed
through pharynx
leaves this way)
nerve cord
notochord
pharynx with
gill slits
oral opening
Agnatha: lamprey eel
Sea squirt: a urochordate
Lancelet: a cephalochordate
Adult
2 Amphibians
2 Teleosts
2 egg-laying
mammals
Some Representative Species of the Phylum Chordata
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Lancelet
dorsal, tubular
nerve cord
Subphylum Cephalochordata;
Class Lancelets
Subphylum name: cephalized as adults. Chordate plan maintained in adults. Genus: Amphioxus found in Tampa Bay
filter-feeders
Genome has been sequenced.
Ciona sea squirt has also been sequenced.
pharynx with gill slits
What Do You Know About Vertebrates?
tail extending
past anus
notochord
segmented
tentaclelike
structures around muscles
mouth
aorta gonad
midgut
hindgut
Subphylum Vertebrata
•  8 major classes:
–
–
–
–
–
–
–
–
Agnatha or jawless fish
Placodermi : 1st jawed fish
Chondrichthyes or cartilaginous fishes
Osteichthyes or bony fishes
Amphibia or amphibians
Reptilia or reptiles
Aves or birds
Mammalia or mammals
anus
pore of
atrial cavity
Class Agnatha: Hagfishes and Lampreys
•  1st lineages to evolve spine & skull
•  Date from Cambrian
–  ±500 Myr ago.
•  Look like large worms or eels •  Highly evolved specialized lineages
•  Lifestyles could only have evolved
after true fish –  Original agnathans were probably filter
feeders.
•  Represented today by 2 lineages
–  Hagfish
–  Lamprey eels
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Placodermi: 1st jawed fish
Class Agnatha: Hagfish and Lampreys
•  Lampreys
–  Parasites with sucker-mouths
–  Problem in Great Lakes
–  Collapse of trout fishing industry
Gill slits:
12 pair
Tentacles
Sucker
•  Armored
•  Extinct
•  Dominant marine predators –  ~ 100 Myr •  Hagfish
–  Scavengers
–  Eat dead or dying fish
Mucous
glands
Gill slits:
7 pair
Jaws evolved from the anterior gill arches of Agnatha.
Chondrichthyes: Cartilaginous Fishes
supporting structures
•  Sharks, Rays, •  Characteristics
Early jawless fish (an agnathan)
–
–
–
–
gill slit
Jaws
Fins
Clear gill slits persist
Mostly marine
•  A few freshwater species
–  Feeding varies
Early jawed fish (a placoderm)
jaw
spiracle (small
gill slit)
Modern jawed fish (a shark)
jaw
support
•  White shark eats sea lion
•  Whale shark filter-feeds
–  small crustaceans
–  other plankton
Skate
Chimera
–  Skates, rays eat ocean-bottom prey
–  Giant manta ray is filter feeder
jaw
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Osteicthyes: Bony Fishes
Osteicthyes: Teleost Fins
•  First vertebrates with bones
–  Replaces cartilage
–  ~ 50 bones form skull around brain
•  Complex circulatory system
Some Teleosts
dorsal fins
•  Supported by rays (bone)
–  countercurrent circulation maximizes
removal of O2 from water
–
–
–
–
–
•  Swim bladder –  Regulates buoyancy
•  Largest living group of vertebrates
–  Poikolothermic (cold-blooded)
–  Adaptations for climates
–  Ray-finned fish
•  Teleosts
•  Largest subgroup
–  Lobe-finned fishes •  Coelocanths
–  Lungfishes
Pectoral (paired)
Pelvic (paired)
Dorsal (vary in number)
Ventral anal fin
Tail fin
caudal fin
anal fin
pectoral fin (1 of 2)
pelvic fin(1 of 2)
Osteicthyes: Lobe-finned Fishes
•  Fleshy ventral fins
•  Only coelocanths survive
–  First seen 1938 off East London, S
Africa
–  Also found near
•  Comoro islands of East Africa •  Malaysia, on the other side of the
Indian Ocean. •  Lung-like sacs
–  Do not function in respiration
–  Gills used for all air exchange
Osteicthyes: Lungfish
•  Freshwater
•  A few relict species
–  South America
–  Africa
–  Australia
•  Lungs allow survival in drought
•  Fossil record 300-400 Myr
–  Relatively unchanged from modern
species •  Distribution suggests origin during
existence of Gondwanaland
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Lungfish on the three southern continents
Amphibians
•  Evolved from lobe- or lung-fishes
•  Adaptations to terrestrial life:
–  Skeletal and muscle changes –  Lungs •  derived from swim bladders?
–  Closed circulatory system
•  delivery of oxygen to tissues
•  Dependence on aquatic habitats
–  Juveniles are aquatic
•  Metamorphosis marks transition
–  Loss of gills
–  Lung function
–  Reproductive maturity
bony or cartiliginous structures in lobed
fin undergoing modification
–  Skins are thin, dry easily
•  Frogs still breathe through skin
limb bones of early amphibians
–  Eggs are soft-shelled
•  Dehydrate if not in water
Amphibians: Orders
•  Frogs and toads
–  Some quite terrestrial
•  Salamanders and newts –  Still rely on very moist habitats
Might best represent earliest forms.
•  Caecilians,
–  Highly evolved
•  Legless •  Look like a cross between an
earthworm and a snake –  (analogy, not homology).
•  Transition to terrestrial life
–  ~ 300 Myr
–  Much later than arthropods, plants
–  Adaptations:
Reptiles
•  Leathery eggs do not dessicate
–  Amnion
»  An additional membrane
inside shell
•  Scaly skins
•  Internal fertilization
•  Swift movement on land
–  Requires new sensory skills
–  Larger brain to process
sensory information
•  Skull became single bony structure
–  Numerous teeth
»  Uniform shape
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Vertebrates: Aves (Birds)
•  Probably a specialized lineage of theropod dinosaurs •  Characterized by
–  Feathers •  Presumably evolved from the scales of reptiles
•  scales still present on legs which they retain on their legs •  Are feathers an adaptation for warm-bloodedness?
–  Loss of teeth –  Formation of a beak •  Beak is analogous to that of turtles and octopi
–  Hard shelled eggs –  Well-developed sternum •  To which their chest flight muscles are attached.
–  Reduction of the “fingers”
•  1-2 digits support primary flight feathers.
yolk sac embryo
chorion
amnion
Mammals
skull
radius
ulna
pectoral
girdle
•  Therapsid lineage
–  ~ 220 Myr
•  Characteristics
humerus
hardened shell
albumin (“white” of the egg)
pelvic
girdle
–  Produce milk in
mammary glands
•  to feed young
–  Hair (or modified hair)
on some part of body
–  Teeth of different shapes
incisors
molars
premolars
canine
sternum
attachment of flight muscles to sternum
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Mammals
•  Derive from therapsid reptiles
–  ca 220 Myr
•  Characteristics:
Placental mammals:
~ 4000 species in 17 orders
Genomes already sequenced: human, chimp, mouse, and rat
Coming soon: orangutan, macaque, cow, possum, wallaby, platypus,
elephant, cat, shrew, tenrec, rabbit, guinea pig –  Hair or fur on some part of body
–  Mammary glands produce milk
•  Nourishment for young
–  Teeth of different shapes
•  Classes
–  Prototheria or monotremes
•  Egg-laying mammals
–  Duck-billed platypus
–  Echidna (spiny anteater)
–  Metatheria or marsupials
•  Young finish development in maternal pouch
–  Opossum
–  Australian megafauna
–  Eutheria or placental mammals
•  Development occurs in maternal uterus There are courses available on subsets of these animal groups:
IB
IB
IB
IB
IB
IB
IB
433
466
460
461
462
463
464
Comparative Vertebrate Morphology
Invertebrate Zoology
Introduction to Entomology
Ornithology
Mammalogy
Ichthyology
Herpetology
Please read chapter 2 in preparation for Monday’s lecture.
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