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Vertebrate Diversity Chapter 34 Chordate Phylogeny Phylum Chordata Bilaterian deuterostomes Derived characteristics Notochord In all embryos and some adults, between digestive tube and nerve cord Provides skeletal support, reduced in humans to vertebral discs Dorsal hollow nerve cord Roll of ectoderm that is unique to chordates becomes CNS Pharyngeal slits or clefts Series of pouches along the pharynx that open to the outside of the body Filter feeding in invertebrates and gas exchange in vertebrates Muscular, post-anal tail Reduced in many species Propels many aquatic species Subphylum Cephalochordata Lancelets have a bladelike shape Retain all 4 characteristics of chordates as adults Filter feeders Gas exchange across body Muscles for movement in and out of sand Subphylum Urochordata Tunicates or sea squirts Short larval stage is a motile bilateraterian with all chordate characteristics Lasts until suitable substrate found when metamorphosis occurs Adult is sessile with degenerated NS, resorbed notocord and tail Suspension feeders Craniates Chordates with a head containing a brain at anterior end of nerve cord, eyes and sensory organs Neural crest distinguishes craniates from other chordates Collection of cells near closing neural tube in developing embryos Cells give rise to teeth, bones of skull, facial dermis, and neurons Pharyngeal slits into gill slits which allow sucking food and gas exchange Higher metabolism, extensive muscles, 2+ chamber heart, RBC’s with hemoglobin, and kidneys Myxini Cartilaginous skull without jaws or vertebrae Muscles against notocord for movement Small brain, eyes, ears, nasal opening, and tooth-like formations of keratin Bottom dwelling scavengers Slime glands Vertebrates More extensive skull Backbone of vertebrae Encloses spinal cord and replaces notocord function Skeletons evolved initially as unmineralized cartilage First structures were dental elements Allowed animals to become scavengers and predators Aquatic species developed dorsal, ventral, and anal fins to provide steering control More efficient means of gas exchange Lampreys Parasites clamp on with jawless mouth and bore into fish to suck blood Larvae is freshwater filter feeder Some feed as larvae only before reproducing and dying Cartilaginous skeleton with no collagen in its matrix Notocord is main axial structure surrounded by cartilage Dorsal projections partially enclosing nerve cord Gnathostomes Jawed animals that are aided by teeth to grip and slice food Evolved from skeletal rods that supported anterior gill slits Forebrain enlargement associated with enhanced vision and smell Lateral line system Organs form rows on either side of body and sense vibrations in water Paired fins and tail enhance swimming after prey Class Chondrichthyans Endokeleton composed of cartilage and Ca+ Bone traces in scales, teeth, and vertebrae surfaces Sharks Swift, but unagile awimmers Bouyancy from oil stored in liver, but must stay swimming Continually replace teeth as lost Spiral valve increases SA of digestive tract Enhanced senses Internal fertilization of eggs Oviparous: lay eggs in protective cases that hatch outside mother Ovoviviparous: retain fertilized eggs in oviducts, nourished by yolk Viviparous: develop in uterus provide nutrients through a placenta Rays Class Osteichthyans Ossified endoskeleton with matrix of calcium phosphate Gills for gas exchange, protected by an operculum Buoyancy from a swim bladder, or air sac, with gas exchange to control rise and fall Skin covered by bony scales Skin glands secrete mucus to skin to reduce drag Most species are oviparous Reproduce by external fertilization after female sheds eggs Actinopterygii Ray-finned fishes Modified for maneuvering and defense Originated in fresh water and spread to seas Salmon and trout between salt and fresh water Human source of protein Sarcopterygii Lobe-fin fishes Muscle surrounds rod- shaped bones For swimming and ‘walking’ across underwater substrate Coelacanths still survive Previously thought extinct Lungfishes Surface to breathe, but gills for gas exchange Tetrapods Tetrapods Limbs that support weight on land Digits on feet to create forces with ground Head separated from neck 1 vertebrae allowed up and down, 2 allowed side to side Pelvic girdle fused to backbone to transfer leg forces to body Pharyngeal slits become ears and glands Class Amphibia Salamanders and newts Some entirely aquatic, others on land or throughout life On land use side-to-side motion Frogs and toads Hind legs to jump Insects and prey caught with tongue Skin glands secrete mucous for protection Color variations as warnings or camouflage Caecilian Legless and nearly blind Absence of legs are secondary adaptations ‘Amphibians’ Life on land and water Herbivorous tadpole is the larval stage of frogs Has gills, lateral line system, and long finned tail; no legs Metamorphosis into a carnivorous adult Develops legs, lungs, external ear drums, and a digestive system; lost gills and lateral line system Salamander and caecilian larvae resemble adult and both stages carnivorous Necessary for skin to stay moist for gas exchange External fertilization in frogs Eggs laid in moist environments to prevent desiccation Oviparous and viviparous species Complex social behavior, ectothermic, cloaca, and 3-chambered heart Amniotes Amniotic egg with 4 membranes Develop from tissue layers growing from embryo Allows embryonic development on land Eggs with shells Differs in birds and reptiles Mammals develop embryo without egg inside female Rib cage helps ventilate lungs Abandon skin breathing and conserve water Class Reptilia Scales of keratin to protect from desiccation and abrasion Eggs on land after internal fertilization Viviparous Ectotherms use heat absorbing behavior instead of metabolism to regulate body temperature Turtles Box-like shields fused to vertebrae, clavicles, and ribs Neck retraction is horizontal or vertical Incubation temperature can determine sex Crocodilians 4 chambered hearts and developed kidneys for excretion Lizards Often carnivorous Snakes Force for movement from bending against objects to move forward Lack ears, but sensitive to ground vibrations Infrared detection All carnivorous with teeth for griping and/or injecting venom Jacobs organ Flexible airway, loosely articulated jaw, and elastic skin to swallow prey Class Aves Features adapted for flight Lack urinary bladders, females with 1 ovary, reduced gonads in both sexes except in breeding season, lightened bones, and toothless Feathers are β-keratin (modified scales) arranged into airfoils Some adapted for soaring others require constant flapping Flightless birds are missing sternal keel and developed muscles Enhanced hunting and scavenging, protection, and food resource attainment Energetically expensive Endothermic animals with layers of fat to provide insulation Efficient respiratory and circulatory system with 4-chambered heart Acute vision and muscle control with larger brain Complex behavioral displays, often related to breeding Internal fertilization via ‘cloacal kiss’ Brooding keeps eggs warm Class Mammalia Mammary glands and hair Endothermic with high metabolic rates Efficient respiratory and circulatory system with 4-chambered heart Diaphragm to help ventilate lungs Larger brains and differentiated teeth 3 lineages Monotremes are egg-laying Marsupials have a pouch Eutherians are placental mammals Monotremes Only in Australia and New Guinea 1 species of platypus 4 species of echidnas (spiny anteaters) Lay eggs, but produce milk and have hair No nipples, milk from glands at belly that young suck Marsupials Higher metabolic rates and nipples Give birth to live young Born early and complete development while nursing in pouch Most live in Australia Opossums only ones in North America Eutherians Longer pregnancy Embryonic development completed in uterus Nurtured by placenta Order Primates 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) Prosimians Lemurs Only in Madagascar Evolved in isolation Ring-tailed lemur Primarily nocturnal Lorises Africa and southern Asia All nocturnal Tarsiers Loris Specialized for vertical climbing and leaping Southeast Asia and Indonesia Diet is almost completely animal matter Tarsier Anthropoids Monkeys (not monphyletic) Active during the day and live in social bands Forelimbs about equal length as hindlimbs New world All arboreal Central and South America Nostrils wide open and far apart Long prehensile tail-specialized for grasping tree limbs Old world Ground dwelling and arboreal Africa and Asia Lack prehensile tail Nostrils open downward Hominoids (Apes) 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 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 Hominoid Divisions (cont.) Chimpanzees (and bonoboos) Knuckle walkers Tropical Africa Behavior closely mirrors humans Make simple tools Respond to mirrors Can learn human sign language Humans Bipedal, larger brain, capable of language, thought, and complex tools Humans didn’t evolve in a direct path. Dead end groups broke off and ended in extinction; except for us.
