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Chapter 34 Vertebrate Evolution and Diversity Phylum Chordata - 3 subphyla: 2 invertebrate subphyla Vertebrata - 4 anatomical features at some point in life: notochord - long, flexible rod between guy and nerve cord - supports adult in some invertebrate chordates - becomes gelatinous material between intervertebral discs in most vertebrates dorsal hollow nerve cord (solid in other phyla) – develops into brain, spinal cord pharyngeal slits - permits water entering mouth from having to travel through entire digestive system (AKA gill slits) - used for suspension feeding in invertebrate chordates - become modified for gas exchange in many vertebrates muscular postanal tail - propulsive force Subphylum Urochordata - tunicates (sea squirts) - marine; adhere to rocks, etc. - filter feeders - no notochord, nerve cord, or tail (only pharyngeal slits) - free-swimming larvae Subphylum Cephalochordata - lancelets (bladelike shapes); marine filter feeders - adults have notochord, nerve cord, gill slits, postanal tail - feeble swimmers Vertebrates neural crest - features: - embryonic cells found only in vertebrates - help form structures such as cranial bones and cartilage greater cephalization - brain and sense organs on anterior end skeleton - cranium and vertebral column as main axis of body axial skeleton cranium - protects brain vertebral column - support ribs - protect internal organs appendicular skeleton - 2 pairs of appendages - 2 major superclasses: Agnatha - no jaws Gnathastomata - have jaws Superclass Agnatha - jawless vertebrates - lampreys - ell-shaped - rasping mouth parts; feed by clamping round mouths onto fish - penetrate skin and feed on blood hagfishes - scavengers; no rasping mouth parts Superclass Gnathastomata Class Chondrichthyes - cartilaginous fishes - skeletons made of flexible cartilage; well-developed jaws; paired fins sharks - streamlined bodies; swift swimmers - tails propel through water - dorsal fin stabilizes; pectoral and pelvic fins for lift - most must swim continuously to provide water flow through mouth and over gills - most are carnivorous; teeth evolved from scales - sharp vision and olfactory sense - lateral line - 2 rows of microscopic organs along flanks - sensitive to water pressure changes and detects vibrations in water - internal fertilization - cloaca - common chamber for reproductive, digestive, and excretory systems rays - bottom-dwellers - flattened bodies - jaws crush mollusks, crustaceans - enlarged pectoral fins for propulsion - whiplike tail Class Osteichthyes - marine and fresh waters - bony skeleton - flattened bony scales cover skin - skin glands produce mucus - lateral line (row of tiny pits on both sides) - gas exchange - water drawn in mouth, through phaynx, and out over gills operculum - covers gill chamber - moves back and forth - swim bladder - dorsal to digestive tract - contains gases; provides buoyancy - flexible fins (maneuverable swimmers) - most have external fertilization Class Amphibia - first vertebrates to move onto land - most stay close to water (damp habitats) - gas exchange through skin - lungs aid gas exchange but are small and inefficient - external fertilization in water - 3 orders of amphibians: salamanders - some aquatic, some terrestrial frogs/toads - enlarged hindlegs for hopping - sticky tongue to capture prey - camouflage; poison skin glands - many metamorphosize - larval stage called tadpole (gills, lateral line, etc.) caecilians - legless ; almost blind - most burrow in tropical soils Class Reptila - several adaptations for land dwelling not seen in amphibians: - scales (made of keratin) to prevent dehydration - lungs - internal fertilization - oviparous - produce amniotic egg (membranes) with leathery shell - prevents drying out - some are viviparous - live young (some snakes, lizards) - ectothermic - absorb solar energy to regulate body temperature - most have 3-chambered heart (not crocs or gators 4) - early reptiles - dinosaurs and pterosaurs (winged) - dinosaurs may have been endothermic (kept bodies warm through their own metabolism) - modern reptiles: turtles - hard shell; all lay eggs on land snakes - probably descended from burrowing lizards - limbless - carnivorous - acute senses; no eardrums but sense ground vibrations - some have heat-detecting organs - flicking tongue carries odors to olfactory organs on roof of mouth - poisonous snakes inject toxin with hollow fangs crocodiles/ alligators - spend most time in water Class Aves - birds - reptilian similarities: amniotic egg (but with hard shell), scales on legs - adaptations for flight: hollow (honeycombed) bones - reduces weight some organs are reduced (only 1 ovary in females) strong pectoral muscles air sacs (reduce body density) - gizzard grinds food - beak - made of keratin; no teeth - endothermic (feathers, fat layer) - 4-chambered heart - feathers - aid in insulation and flight - made of keratin (evolved from scales) - efficient circulatory system; 4-chambered heart (separates oxygenated from unoxygenated blood) - efficient lungs attached to air sacs - well developed nervous systems; complex behaviors - internal fertilization - wings Archaeopteryx - share a common ancestor with modern birds - clawed forelimbs, teeth, long bony tail, feathers - may have been a tree glider Class Mammalia monotremes marsupials - hair made of keratin for insulation - endothermic - efficient respiratory system with a diaphragm - 4-chambered heart (separates oxygenated from unoxygenated blood) - mammary glands - produce milk - teeth of various sizes and shapes - internal fertilization; most viviparous (placenta nourishes embryo) - large brains; capable of much learning - parent scare for young - egg-laying mammals (oviparous) - platypuses, echidnas - hair, mammary glands - opossums, kangaroos, koalas, etc. - young born early; use forelimbs to climb from mother reproductive tract to marsupium - marsupium - “pouch”; young attaches to a teat to complete development placental mammals - embryonic development completed in uterus - placenta joins embryo to mother some orders: Chiroptera - bats (wings, nocturnal, some eat blood, some fruit) Insectivora - shrews Lagomorpha - rabbits Perissodactyla - odd-toed ungulates (horses, rhinos, etc.) Artiodactyla - even-toed ungulates (shhep, deer, etc.) Sirenia - sea cows Proboscidea - elephants Cetacea - whales, dolphins Carnivora - cats, dogs, raccoons, seals, bears Rodentia - rats, squirrels, beavers Primates - monkeys, apes, humans Primates - dexterous hands with opposable thumbs - sensitive fingers; nails (no claws) - eyes close together on front of face (enhanced depth perception) - prental care Old World Monkeys - Africa, Asia - tree and ground dwellers New World Monkeys - South America - all tree dwellers Apes - 4 genera: gibbons orangutans gorillas chimpanzees - large legs, short legs, no tails - gorillas and chimps highly social - larger brains than monkeys (more adaptable behavior) Paleoanthropology - study of human origins and evolution first humans Australopithecus africanus - discovered 1924 (brain 1/3 that of modern humans) - “Lucy” discovered in 1974 (40% complete) Homo habilis - larger brain, walked upright, used tools Homo erectus - first hominid to migrate from Africa into Europe and Asia - taller and larger brain than Homo habilis - lived in huts or caves, built fires, wore animal skins, designed more refined tools - descendants - Neanderthals - Homo sapiens Homo sapiens - could change environment to meet its needs - didn’t need to adapt to environment through natural selection - may be changing the world faster than species can adapt - overwhelming rate of extinction due to habitat destruction and pollution - global warming due to fossil fuel consumption - destruction of tropical rain forests (which help maintain gas balance & moderate global weather) - may be creating the most devastating crisis in the history of life!