Transcript Vertebrates
Vertebrates Chapter 34 Phylum Chordata • Bilaterally symmetrical • Deuterostomes • Contain 2 subphyla of invertebrates – Tunicates and lancelets – Hagfishes • Vertebrates Related Based on shared body plan features (coelom, symmetry, etc.) Milk Amniotic egg Legs Lobed fins Lungs Jaws Vertebral column Head Brain Notochord 4 Key Characteristics of Chordates -Notochord – longitudinal, flexible rod -Hollow nerve cord -Pharyngeal slits -Post-anal tail, often lost post-embryo Notochord – SUPPORT (not a nerve cord) Notochord remnant in inter-vertebral discs Tunicates -Larvae have chordate morphology -Use tail muscles and notochord to swim to substrate, settle in -Radical metamorphosis to adult Lancelets - Larvae have chordate traits - Maintain chordate traits as adult (still larva-like) Expression of developmental genes -Lancelets use Hox genes to form cranial bulb -Vertebrates use same Hox genes to form more elaborate brain What next? How about a head? Craniate development What’s a Vertebrate? • Possess neural crest (embryonic cells) They form: -Bones and cartilage of cranium - neurons and sense organs What’s a Vertebrate? CEPHALIZATION (“getting a head”) - Cranium, brain, eyes, ears, nose concentrated at head end of animal – helps with active lifestyle What’s a Vertebrate? Bilateral symmetry = dorsal, ventral, left, right, cranial, caudal (tail) directions make sense What’s a Vertebrate? • Vertebral column Derivatives of pharyngeal slits and bars in vertebrates • Jaws, jaw support • Gills and gill supports • Aortic arches and other important blood vessels • Some muscles Human embryo – 4.5 weeks Dog Bat Hare Man Vertebrates • Respiratory and circulatory adaptations to support active tissues, efficient hearts • Closed circulatory system (blood stays in vessels) • Diverse adaptations for feeding and digestion Vertebrates have• Strong axial skeleton Strong, diverse appendicular skeletons (with limbs); extensive use of bone Vertebrates Jawless Fish Hagfish - have cartilage skull and notochord, no vertebrae - Parasitic or scavengers - tooth-like structures (keratin) Lamprey -Notochord and vertebra-like projections -Rasp-like teeth, no mineralized bone Jawed Fish -Strong, complex internal skeletons (cartilage or bone) -Well developed appendages (fins) -Jaws – open diverse new feeding opportunities, eat larger food particles -Bony fish – most diverse group of vertebrates -Both groups evolved from ancestors with bony skeletons (regression of bone in sharks) Cartilage fish Bony fish Jawed Fish • Sharks and Rays – Cartilage skeleton, some ovoviviparous/ – have a cloaca (one exit only) • Ray-finned fish – Bony skeleton/bony scales – Gills covered by operculum • Lobe-finned fish – Rod-shaped bones in pectoral and pelvic fins – 3 lineages alive today • Coelacanths • Lungfishes • Tetrapods Amphibians Amphibians – frogs, toads, salamanders, caecilians (legless, worm-like) First tetrapods (= “four-footed) = terrestrial Reproduction in most amphibians tied to water (eg. Tadpoles and frogs) External reproduction, some spp. have metamorphosis (frogs) Require water or damp habitat, many use moist skin for gas exchange Amniotes • All have amniotic egg with extraembryotic membranes (not part of embryo’s body) • In reptiles, birds and some mammals egg has a shell – Allows wider habitat than amphibians • In other amniotes, development in the mother Amniotes Reptiles Reptiles – first successful terrestrial vertebrates Skin very resistant to water movement (scales with keratin) Rib cage movement ventilates lungs Reptiles • Clade includes lizard, snakes, turtles, crocodilians and BIRDS! • Most are oviparous, shelled eggs laid on land – Many spp of snakes and lizards are viviparous (live birth) • Most are ectothermic (absorb external heat) – But, birds are endothermic (internal heat) Birds • Have many body adaptations for flight, eg. Wings, feathers, hollow bones, cloaca, gonads • Flight benefits in hunting, escape, and migration • Other adaptations allow for fitting niches – Egs. Foot structures • Origin of birds observed in fossil record – archaeopteryx Mammals Evolved from reptiles Have mammary glands, produce milk Placenta in most mammals – nourishment, protection of embryo during development Three groups Eutherians – humans, dogs, deer, mice, etc. Marsupials – opossums, kangaroos Monotremes – egg-laying mammals Primates • • • • • Eutherians – development in placenta Grasping hands (and feet) Opposable thumbs Close-set eyes Complex social behavior – Extensive parental care Monkeys and Apes • Monkeys – Tail, prehensile in New world • Apes – No tail, long arms – Includes gorillas, chimps and humans Hominids • Lineage that diverged from common ancestor of chimpanzees and humans • Lineage based on extensive fossil record Are humans evolved from apes? NO! Humans • Bipedal • Large brain – Tool use, language, art and culture (a good thing?) • Disorderly progression from progenitors