Animals III: Chordates and Animal Development

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  1. All chordates possess all four of the following key characteristics at some time in their life cycle:
    • a slender, solid rod of cartilage-like connective tissue called the notochord; dorsal surface, serves as an endoskeleton, replaced by bone or cartilage in the vertebrates
    • a series of paired slits along the pharynx, called pharyngeal gill slits; supporting structures called gill arches are modified in higher vertebrates into the inner ear bones and the jawbone
    • a dorsal, hollow, single nerve cord
    • post-anal tail
  2. chordata body plan
    • triploblastic
    • eucoeolomate
    • bilaterally symmetrical
    • deuterostomes
    • show to a varying degree some segmentation, at least internally
  3. additional features of chordates
    • extracellular digestion
    • closed circulatory system with a contractile heart
    • kidneys containing many nephrons
    • gills or lungs for gas exchange
    • primarily dioecious; fertilization could be internal or external
    • allows for an active lifestyle, high metabolic rates, and large size
  4. Urochordata
    integumentary and skeletal systems
    • tough cellulose-like polysaccharide (tunicin) that forms the tunic or outer covering, which provides protection and support
    • some calcareous spicules
    • incurrent siphon brings in water into the atrium, the water then passes through the pharyngeal basket, which filters the planktonic food, water then leaves our the excurrent (atrial) siphon
  5. Urochordata
    osmoregulatory/excratory systems
    • elimination primarily by diffusion
    • blood is isotonic to seawater
  6. Urochordata
    digestive systems
    • complete
    • endostyle - gland associated with the pharyngeal basket, produces mucus, which in turn entraps food; carried by ciliary action to the esophagus
    • extracellular digestion in stomach
  7. Urochordata
    nervous systems
    • series of ganglia found in various places
    • sensory systems are located in the anterior part
    • brain not well-developed
  8. Urochordata
    circulatory and respiratory systems
    • heart and open circulatory system
    • gas exchange occurs between the water and the blood in vessels located in the pharyngeal basket
    • no respiratory pigments
  9. Urochordata
    muscular systems
    • larvae are mobile, but most adults are sessile
    • adults have lost notochord
    • circular and longitudinal muscles found in the body wall
    • filter feeders
  10. Urochordata
    reproductive systems
    • monoecious
    • shed gametes into the water column out the excurrent siphone (external fertilization)
    • brood the fertilized eggs in the pharyngeal basket (internal fertilzation)
    • undergo asexual reproduction by budding
    • regeneration of lost parts
  11. Cephalochordata (amphioxus, lancelets)
    oral hood structure
    • anterior
    • finger-like cirri that act as sensors and strain out food
  12. Cephalochordata
    muscular systems and locomotion
    • myomeres along the sides of the amphioxus are segmented muscles
    • dorsal and caudal fin
  13. Cephalochordata
    integumentary and skeletal systems
    • notochord acts as a support structure for both the oral hood and provides a rigid structure for muscles to work against
    • notochord is retained in adult
    • body wall not covered by a test or with scales
  14. Cephalochordata
    nervous systems
    • hollow nerve cord is dorsal of the notochord
    • no cephalization
    • segmental nerves
    • an eyespot at anterior end
  15. Cephalochordata
    digestive systems
    • buccal cavity, where the mouth is located
    • finger-like structures, collectively called the wheel organ, are in the pharynx; attached cilia beat to create a current
    • pharynx has a series of parallel gill bars, through which water passes; food is trapped in the mucus, produced by the endostyle
    • trapped food and mucus passes dorsally up to the epibranchial groove, and thus intestine, hepatic cecum, and anus
    • water leaves out through the atriophore
  16. Cephalochordata
    circulatory and respriatory systems
    • gas exchange occurs via diffusion, especially at the gill bar epithelium
    • no blood cells or respiratory pigments
    • closed circulatory system
    • no distinct heart
  17. Cephalochordata
    osmoregulatory/excretory systems
    • nitrogenous wastes eliminated via protonephridia
    • analagous to the protonephridia of flatworms and primitive annelids
  18. Cephalochordata
    reproductive systems
    • dioecious
    • external fertilization
  19. Subphylum Craniata characteristics:
    • nerve cord, notochord, and neural crest - nerve cord from s from a layer of ectodern cells; another group of cells forms the neural crest, which cells eventually form parts of the cartilage and bone in the skull
    • a cranium (skull) protecting the brain
  20. Agnathans
    • jawless craniate animals
    • includes lampreys and hagfishes
  21. Class Myxini (hagfish) characteristics
    • predatory/scavengins species with a rapsing tongue
    • skeleton composed of cartilage
    • lack jaws and vertebrae
    • retain notochord as support structure
    • slime glands
    • no paired appendages
    • possess one pair of semicircular canals
    • lack scales
    • have pore-like gill slits
    • circulatory systems with hearts
    • gills for respiration
    • body fluids are iso-osmotic with seawater; little capacity to regulate water concentration
    • no independent larval stage
  22. Vertebrate characteristics:
    • vertebrae made of bone/cartilage
    • endoskeleton that grows with the animal
    • integument that consists of an inner dermis and an outer epidermis
    • kidneys with nephrons
    • hearts, red blood cells, hemoglobin, and a close circulatory system - allows for rapid movement of bodily materials
  23. Class Cephalaspidomorphi (lampreys)
    • ammocoete larvae live in freshwater streams for several years, and then return to the sea if marine species
    • ectoparasites on fish
    • persistent notochord that becomes partially enclosed by cartilage, with extensions that surround the nerve cord
    • skeleton made of cartilage
    • lack jaws and paried appendages
    • pore-like gill slits
    • circular mouth with keratinized teeth, a sucker-like oral disk, and a rasping tongue
    • well-developed eyes
    • possess two pairs of semicircular canals
    • body fluids are osmotically and ionically regulated
    • seven pairs of gills
    • closed circulatory system similar to fish; heart consists of two chambers
  24. ammocoete larvae of lampreys
    • show all four key chordate characteristics
    • live as larvae for long periods of time then develop into short-lived parasitic adults
    • suspension feeders
    • several characteristics that are homologous to higher vertebreates - two-chambered heart, a three-part brain (forebrain, midbrain, hindbrain), thyroid and pituitary glands, kidney
  25. Gnathostome characteristics:
    • jaws and teeth - allows for capture and rapid ingestion of foods, macerating the food prior to digestion, increases the surface area of the prey tissues to facilitate digestion
    • paired limbs (pelvic and pectoral limbs)
    • three pairs of semicircular canals
    • advanced sensory organs
  26. jawed fishes
    • aquatic gnathostome vertebrates include chondrichthyes and osteichthyes
    • use gills for respiration
    • reproduction styles vary from oviparous, ovoviviparous, viviparous
    • closed circulatory system with two-chambered heart
  27. oviparous
    lay eggs that hatch externally
  28. ovoviviparous
    lay eggs that hatch in the female's reproductive system
  29. viviparous
    bear live young; no eggs laid initially
  30. Class Chondrichthyes (cartilaginous fish)
    • sharks, skates, rays, and relatives
    • cartilaginous endoskeleton is a derived character (ancestors had bony skeleton)
    • placoid scales
    • tail provides propulsion, fins are stabilizers
    • buoyancy maintained by large amounts of oils stored in the body
    • must continuously swim in order to remain in the water column
    • dioecious; internal fertilization
    • blood is iso-osmotic to seawater
  31. Osteichthyes include 3 groupings:
    • ray-finned fishes - fins are supported by thin, parallel bony rays; no muscles in the fins
    • lobe-finned fishes - fleshy muscular lobes in their fins; lobes contain articulated bones that are extensions of the pectoral and pelvic areas; fin rays can be moved independently by lobe muscles
    • lungfishes (Class Dipnoi)
  32. Bony fishes:
    • skeleton made of bone
    • air-filled swim bladders; help conserve energy by remaining stationary
    • gas exchange occurs by drawing water over the 4-5 pairs of gills located in gill chambers covered by the operculum, a protective flap of tissue
    • scales help to prevent water diffusing across the skin; mucus glands
    • osmoregulation is a function of both the gills and the kidneys; kidney contains nephridia that filter ammonia and other wastes from the blood; kidney regulates water and salt concentrations within the fish's body
    • closed circulatory system with a two-chambered heart that pumps blood that travels in a single loop through the body
    • dioecious; external fertilization; oviparous, eggs contain a large amount of yolk
    • well-developed brain, spinal cord
    • lateral line system that can detect small changes in water movement; adapted to electrical fields
    • primary carnivorous; complete digestive tract with regional specialization
    • blind finger-like appendices, pyloric caeca, are attached to the intestine; secrete digestive enzymes
  33. Tetrapoda
    • evolved from lobe-finned fishes
    • four-limbed animals
  34. Class Amphibia
    • frogs, toads, salamanders
    • four limbs with toes
    • must return to water to lay their eggs (which lack a shell)
    • dioecious; external fertilization
    • have to stay moist if on land, skin is a major respiratory organ
    • closed circulatory system with three-chambered heart - potential disadvantage is that oxygenated and deoxygenated blood may mix; separate pulmonary and systemic circulatory systems (double circulatory system)
    • skeleton is modified from basic fish plan
    • minimize evaporative water loss by primarily being nocturnal and residing in humid habitats
    • carnivorous with complete digestive tract
    • larvae and some adults have lateral line organs (similar to fish)
    • larvae (tadpoles) must live in water; typically reabsorbs its tail and undergoes metamorphosis by gradualling growing limbs; adults can be aquatic or terrestrial
  35. Amniotic egg
    • evolution of the amniotic egg helped the successful establishment of vertebrates on land
    • shelled to prevent desiccation
    • series of extraembryonic membranes that help the embryo develop totally inside a terrestrial egg
    • consists of the chorion, allantois, yolk sac (yolk and albumin), and amnion
  36. extraembryonic membranes of the amniotic egg:
    • chorion - invovled in gas exchange, water conservation, produces placenta
    • allantois - stores wastes other than ammonia, water conservation, gas exchange, produces placenta
    • yolk sac - surrounds the yolk; the yolk and albumen provides nutrients
    • amnion - surrounds the embryo, prevents dehydration and cushions the embryo
  37. Amniote characteristics:
    • closed circulatory system with a 3-4 chambered heart
    • eliminate urea as metabolic wastes; more advanced excretory systems; do not use ammonia as major waste product because of large amount of water needed to flush ammonia from body (water conservation is key in terretrial environments)
    • tough leathery skin that protects them against desiccation and physical injury
    • strong jaw muscles that provide more mechanical advantage to crush or grip prey; jaws come from modification of the pharyngeal slit arches
    • internal fetilization; needed for a shelled egg
    • more efficent circulatory system with higher blood pressures
    • more efficient lungs
    • muscles of the rib cage help ventilage the lungs
    • negative pressure breathing system
  38. Class Reptilia
    • snakes, crocodiles, turtles, lizards, dinosaurs
    • evolved into mammals and birds
    • four limbs with toes (absent in snakes and some lizards)
    • amniotic egg assisted in land colonization; egg covered with a calcareous or leathery shell
    • no free-living larval stages
    • oviparous
    • internal fertilization
    • dioecious
    • scales made of keratin (hair/mammals and feathers/birds are modified scales)
    • periodically shed outer epidermal layers in ecdysis; dry skin
    • efficient lung for gas exchange
    • three chambered heart - centricle is incompletely divided into two, thus functionally acting as two distinct chambers
    • double circulatory system with nucleated red blood cells
    • ectotherms - maintain a constant internal temperature via behavioral adaptations
    • body supported by limbs and girdles (pelvic and pectoral)
    • metanephric kidneys with uric acid as metabolic wastes
    • complete digestive systems with regional specailizations for acquiring, storing, and digesting food; primarily carnivores
  39. Class Aves
    • modified scales called feathers, which are involved in flight and thermoregulation
    • oviparous (lay calcareous shells)
    • fly due to - feathers, strong pectoral muscles, strong and light bony skeleton; most bones are hollow
    • four-chambered heart and double circulation
    • efficient respiratory system with air sacs
    • endotherms
    • nucleated red blood cells
    • possess a single bone in a middle ear
    • no teeth are present; horny sheaths around jaw made of keratin; beak adapted for various tasks
    • uric acid is main metabolic waste; efficient kidneys with nephrons
    • salt glands that function in osmoregulation
    • single cloaca, no bladder
    • well-developed brain with large cerebrum; cabable of complex instinctive and learned behaviors
  40. Class Mammalia
    • leahtery skin with modified scales called hair, sweat glands
    • evaporative cooling
    • mammary glands that produce milk to nourish young
    • teeth are modified for different functions (incisors, canines, molars; heterodonts, homodonts)
    • modifications of bones of the ancestral reptile jaw create the three inner ear bones/auditory ossicles
    • secondary palate which separates the oral and nasal cavities; both breathe and hold things in their mouth
    • efficient respiratory system with a muscular diaphragm that helps ventilate the lungs
    • endothermic
    • four-chambered heart; double circulation
    • non-nucleated, biconclave red blood cells
    • dioecious; internal fertilization
    • oviparous monotremes, viviparous eutherian mammals; placenta transfers nutreints, gases, and wastes between mother and offspring
    • urea as main metabolic waste; kidneys and nephrons are highly advanced, involved in both osmoregulation and excretion; bladder
    • variety of feeding styles
    • highly specialized and advanced brains; cerebrum is highly convulute, which increases the surface area where cell bodies of neurons can be located
  41. teeth types
    • incisors - shearing
    • canines - tearing
    • molars - grinding
  42. heterodonts
    • single animal with different types of teeth
    • includes most mammals and some reptiles
  43. homodonts
    • single animal with only one basic type/shape of tooth
    • includes amphibians, fish, and some reptiles
  44. major stages of seastar development:
    • unfertilized egg
    • fertilized egg
    • 2-cell, 4-cell, 8-cell stage
    • morula stage
    • blastula stage
    • gastrula stage
    • bipinnaria stage
    • brachiolaria
    • embryonic development is basically the same in all animals until a certain stage
  45. unfertilized egg
    see the nucleus and nucleolus
  46. fertilized egg
    • sperm and egg pronuclei are about to combine
    • wrinkled fertilization membrane may be seen
  47. 2-cell, 4-cell, 8-cell stage
    • mitosis (cleavage)
    • holoblastic cleavage - blastomere completely divides into two separate cells of roughly equal size
  48. morula stage
    • 16-64 cells
    • solid ball of cells
    • does not have a definite blastocoel (central cavity)
  49. blastula stage
    • blastocoel appears
    • cilia develop
  50. gastrula stage
    • embryo begins to elongate and you will see the archenteron (primitive gut)
    • opening to the archenteron is the blastopore
    • cells that line the archenteron will form the endoderm
    • outer layer of cells of the gastrula form the ectoderm
    • coelomic vesicles can be observed forming off of the end of the archenteron; these pouches eventually form the coelom; these cells are part of the mesoderm
  51. bipinnaria larva
    mouth develops, larva begins to feed; after the brachiolaria stage, the larva settles to the bottom and metamorphoses into the adult echinoderm
Card Set:
Animals III: Chordates and Animal Development
2012-04-04 04:21:58
Bio 244 lab

Unit 20
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