Evolution of Vertebrates

1. Evolution of Vertebrates Chapter 19

2. Chordate Characteristics • Dorsal, hollow nerve cords • Notocord between GI tract and nerve cord • Pharyngeal slits • Post-anal tail

3. Phylum Chordata • Subphylum Urochordata • Sea squirts • Adult has pharyngeal slits only, larva has all four • No brain • Subphylum Cephalochordata • Lancelets • Suspension feeders • Mucus net to trap food • Simplistic brain, swollen tip of nerve cord • Subphylum Craniata • Species with a head containing a brain, sensory organs, and a skull

4. Development of Vertebrates

5. Class Agnatha (Jawless fish) • Chordates with heads, no jaws, and a notocord for support • Hagfishes • Nearly blind, but excellent sense of smell and touch • Enter holes in prey or create holes with tooth structures • Ties tail in knots or secretes slime for feeding and protection • Lampreys • Larvae are suspension feeders that live in sediment • Most are parasitic to fishes • Attach to sides of fish and feeds on tissue and blood • From ocean to Great Lakes by St. Lawrence Seaway

8. Class Chondricthyes (Cartilaginous fishes) • Flexible skeletons of cartilage • Lateral line system to detect changes in water pressure and vibrations • Sharks • Detect prey through electrosensor s on their head • Sharp vision and keen smell • Rays • Suspension feeders • Dorsoventrally flattened with eyes on top of head • Tails have spines that have venom glands

10. Class Osteichthyes (Bony fishes) • Ray-finned fishes • Skeleton made of bone including the ray fins • Operculum , protective flap covering the gills • Can breathe without swimming, contrast shark • Swim bladder, lung-derived organ to keep them afloat • Adaptaions based on environment • Female seahorses deposit eggs in male’s pouch to develop • Lobe-finned fishes • Rod shaped bones in pectoral and pelvic fins • Coelocanth, lungfishes, and tetrapods

11. Class Amphibia • Damp habitats so water can supplement for lungs • Skin has poison glands and coloration for defense • Distribution limited by vulnerability to dehydration • Caecilians • Nearly blind and legless • Live in moist tropical areas • Frogs • Most adult life on land • Lay eggs in water and juveniles (tadpoles) live in water until metamorphosis • Toads have rough skin and entirely terrestrial • Mating calls during breeding season

12. Class Reptilia • Amniotes, eggs develop in protective sacs • Include lizards, snakes, turtles, crocodilians, and dinosaurs • Skin with scales and waterproofed by keratin • ‘Cold-blooded’ so metabolism doesn’t make heat • Ectothermic absorbs heat • Dinosaurs may have been endothermic, using metabolism • Snakes lost legs due to burrowing nature • Crocodilians most time in water with nostrils out

13. Class Aves • Evolved from small, 2-legged dinosaurs (therapods) • Body adapted for flight, strong but light • No teeth, tail has few vertebrae, feather shafts hollow, and honeycombed bones • Feathers provide lift and maneuverability • High metabolism for energy demands of flight • Endothermic so feathers act as insulation • Highly efficient circulatory system, lungs, and vision • Complex behavior, both sexes incubate eggs and feed

14. Class Mammalia • Hair and mammary glands that produce milk • Endothermic so hair acts to insulate • Efficient respiratory and circulatory systems for high metabolism • Large brain and long parental care • Differentiation of teeth for variety of foods • Offspring are hatched or birthed

15. Order Monotremata (Monotremes) • Egg-laying mammals • Duck-billed platypus and spiny anteaters are only existing members

16. Subclass Theria • Embryo is nurtured in the mother by a placenta • Allows nutrients to diffuse between mother’s and embryo’s blood • Infraclass Metatheria (Marsupials) • Brief gestation • Tiny offspring that develop in an external pouch • Infraclass Eutheria (Eutherians) • Bear fully developed live young • Placental animals because more complex then marsupials

17. Order Primates (Human order) • Opposable thumb and big toe • Aids grasping and manipulation behaviors • Adapted for arboreal (tree-dwelling) life • Flat nails and not claws • Reduced olfaction, but increased reliance on vision • Smaller noses, but larger eyes in front close together • Smaller litter size, longer gestation, increased maternal care • Fewer teeth, but specialized • 2 incisors, 1 canine, 3 premolars, and 3 molars in each quadrant • 2 taxonomic arrangements (generally)

18. Prosimians • Lemurs • Only in Madagascar • Evolved in isolation • Primarily nocturnal • Lorises • Africa and southern Asia • All nocturnal • Tarsiers • Specialized for vertical climbing and leaping • Southeast Asia and Indonesia • Diet is almost completely animal matter Ring-tailed lemur Loris Tarsier

19. Anthropoids • Monkeys (not monophyletic) • Active during the day and live in social bands • Forelimbs about equal length as hindlimbs • New world • Central and South America • Nostrils wide open and far apart • Long prehensile tail-specialized for grasping tree limbs • Old world • Africa and Asia • Lack prehensile tail • Nostrils open downward • Hominoids (Apes)

20. Hominoids (Apes) • Lack tails • Long arms and short legs • Mainly vegetarians • Humans are omnivorous, eating plants and animals • More flexible • Larger brain relative to body size • High degree of social organization • 5 divisions

21. Hominoid Divisions • Gibbons • 9 species all in Southeast Asia • Only entirely arboreal apes • Smallest, lightest and most acrobatic • Monogamous for life • Orangutan • Solitary species in rain forests of Sumatra and Borneo • Largest arboreal mammal, occasionally move on ground • Gorillas • Largest ape found only in African rainforests • Live in groups of up to 20 • Stand upright, walk on 4 legs with knuckles on the ground

22. Hominoid Divisions (cont.) • Chimpanzees (and baboon) • Knuckle walkers • Tropical Africa • Behavior closely mirrors humans • Make simple tools • Respond to mirrors • Can learn human sign language • Humans • Hominid fossils found that are closer to humans than chimpanzees • Human evolutionary branch, but don’t confuse with hominoid

23. From Hominoid to Hominid • Initial theory • Increased brain size credited with divergence • Led to changes in food-gathering skills, parental care, and social interactions • Bipedalism, upright walking , afterwards • Hypothesis untested till female skeleton, ‘Lucy’, found • Bipedilism conclusively shown to emerge first • Opening at base of skull supports upright evolution • Quaprepeds have openings that angle back • Stephen Gould, “mankind stood up first, and got smart later.”

24. From Hominid to Homo • Evidence from fossils and comparing to earlier species • Increased skull size relative to brain can estimate brain size which can indicate intelligence • Complexity of tools found • Changes in teeth and jaws • Smaller to adapt to meat eating and allow brain growth in skull • Long, slender legs with hip joints for distance walking • Narrow pelvis constrained fetal head size so parental care needed for longer

25. Homo sapien Spread • All living humans suggested to originate from ancestors in Africa • Mitochondrial DNA, inherited maternally • All trace to one common woman • Y chromosomes, passed from father to son • Mutations can serve as markers for ancestry • Believed to spread because of increased cognition • Capacity to speak strong factor

26. Emergence of Speech • Human language is unique • Other animals vocalize sounds to communicate • Human communication is more complex which creates societies with shared language • Used in concrete and abstract ways • FOXP2 gene linked to a family with impaired speech and brain development • Found in other species • Humans and song-birds are most similar • Both learn vocalization from others of the species • Linked to brain development of speech area • Other genes contribute, but connected to passing on

27. Skin Color • Skin color varies geographically • One of the most striking differences • Not genetically distinct • Results from melanin, a pigment of specialized skin cells • Activity levels effect degree of pigmentation • Absorbs visible and UV light • Synthesizes vitamin D, necessary for bone development • Less pigment adapted to maximize vitamin D as moved north • Protects folate degradation • Necessary for fetal development • Damaged by UV light

28. Pigmentation Trade Off • Hypothesized as an adaptation trade off • Balanced folate protection with vitamin D production • Similar environments have similar pigmentations • Not a useful phylogenetic character