Lophotrochozoa = No moult, spiral cleavage
Ecdysozoa = Moult
Protostomia = Mouth 1st
Bilateria = Bilateral symmetry, triploblastic
Eumetazoa = True tissues
Metazoa = Animalia
Deuterostomia =
Mouth 2nd, radial
cleavage
Fig. 14.1
2
Summary: Echinoderms & Hemichordates
• Deuterostomes – ‘second mouth’ (blastopore → anus)
• Different cleavage & development than Protostomes
• Includes closest invertebrate relatives to chordates.
• Clade Ambulacraria:
• Phylum Echinodermata – 5 classes, various ecological strategies
• Phylum Hemichordata – not chordates
• Echinoderm features:
• Pentaradial symmetry is secondarily derived (larvae – bilateral)
• Water vascular system
• Dermal ossicles => “endoskeleton”
• Some groups have pedicellariae
• Regeneration (autotomy)
• Catch collagen (mutable collagen)
• Ecologically, may be very important (keystone species)
3
Deuterostomes
Fig. 15.3
Summary: Chordate Origins
• Phylum Chordata
• Protochordates
– Subphylum Urochordata (= Tunicata) – tunicates/sea squirts
– Subphylum Cephalochordata – lancelets
• Subphylum Vertebrata
• 5 Chordate Characters
1. Notochord
2. Dorsal hollow nerve cord (DHNC)
3. Pharyngeal slits
4. Endostyle/Thyroid
5. Postanal tail
• Key steps in vertebrate evolution
• Endoskeleton/muscle changes
• Physiological upgrades (gills)
• Neural crest & ectodermal placodes
• Paired fins & jaws
Cladogram of Phylum Chordata
Figure 15.2
Cladogram of the Fishes
Fig. 16.2
7
Summary: Agnatha & Chondrichthyes
• Phylum Vertebrata
• Agnatha
• Cyclostomata
‒ Myxini – Hagfishes
‒ Petromyzontida – Lampreys
• Ostracoderms (extinct)
• Gnathostomata (jaws + paired appendages)
• Placoderms (extinct)
• Chondrichthyes
‒ Elasmobranchii
‒ Holocephali
Actinopterygii = ray-finned fishes
3 main clades
1. Cladistia (“clad” = branch; “istia” = tissue)
•
bichirs (13 spp.)
2. Chondrostei (“chond” = cartilage; “os” = bone)
•
sturgeons, paddlefish (27 spp.)
3. Neopterygii (“neo” = new, modern; “pter” = fin)
•
modern ray-finned fish (> 29,600 spp.)
Sarcopterygii (lobe-finned fishes)
Coelacanth (2 spp.) & Lungfish (6 spp.)
• Gills & lungs
• Fleshy fins with muscle & bone
• Diphycercal caudal fin
• Spiral valve!
• Notochord persists!
→ Extinct form gave rise to tetrapods
Fig. 16.13
Summary – Osteichthyes (Ch. 16 – Part B)
• Evolution and classification
• Actinopterygii and Sarcopterygii
• Features and basic anatomy
• Locomotion – moving faster!
• Endothermy
• Buoyancy – going “up”? (or “down”)
• Respiration – gills and countercurrent gas exchange
• Osmoregulation – keeping the water “in” (or “out”) to survive
• Reproduction – where and how many times
• Anadromous and catadromous
• Semelparous and iteroparous
• Sarcopterygii – Tetrapod ancestor
Early Tetrapod & Amphibian Evolution
Amniotes
Fig 17.3
Lissamphiba: Modern Amphibians
(> 7,900 spp.)
Class Amphibia (= “both kinds of life”)
1. Order Gymnophiona (“naked of a snake”) – caecilians
2. Order Urodela (“tail evident”) – salamanders
3. Order Anura (“without tail”) – frogs & toads
Amniotes
Early diversification produced 3 patterns of fenestrae
➢anapsid (ancestral), diapsid, & synapsid
Adaptations of Amniotes
Derived features of Amniotes
1. Amniotic egg
2. Keratinized (waterproof) skin
3. Rib (costal) ventilation of the lungs
4. Stronger jaws
5. High pressure cardiovascular system
6. Water-conserving nitrogen excretion
7. ↑ brain & sensory organs
Modern Bird Groups (living birds = Neonithes)
Neognathae
(=“new jaw”)
Flying birds
(99% of birds)
Paleognathae
(=“old jaw”)
Flightless (ratite) birds
Characteristics of Aves (150 my of evolution)
see box on page 416
1)
2)
3)
4)
5)
6)
7)
8)
Neck long & S-shaped
Feathers & leg scales
Forelimbs → wings (not all fly)
Hindlimbs → walk, perch, swim
Endothermic
Beak (keratin) → no teeth
Eggs
Modified skeleton
e.g., pygostyle, synsacrum, sternum
Evolution of Synapsids
Fig. 20.1
Earliest Synapsid Groups
➢ “Stem Mammals”
➢ paraphyletic groups
Pelycosaurs
• Differentiated teeth
Therapsids
• Erect gait with upright limbs
beneath body
Cynodonts
• Heterodont teeth
• 2° palate
• Loss of lumbar ribs → diaphragm
• Turbinates
Early Mammals of Late Triassic
Small (mouse-sized), with many Mammal Features:
• Heterodont teeth & 2° palate (cynodont ancestor)
• Diphyodont dentition (replaced once)
• Lower jaw = 1 bone (Dentary bone)
– 2 other jaw bones → middle ear
• New jaw joint = squamosal-dentary joint
–defining characteristic for fossil mammals (“mammalian forms”)
More Mammal Features
• Endothermic
‒early forms probably not as warm
• Hair
• Diaphragm
• Skin glands
• Mammary glands → lactation
–probably evolved in late Triassic
• 3 ear ossicles (middle ear bones)
& ectotympanic (holds ear drum)
–modified jaw bones (better hearing)