Protostomes i Deuterostomes

Protostomes and Deuterostomes

• Protostomes: The mouth forms first, then the anus, during embryonic development. Examples include arthropods, molluscs, annelids, platyhelminthes, nematodes, rotifer, and nemertins.
• Deuterostomes: The anus forms first, then the mouth, during embryonic development. Examples include echinoderms, hemichordates, and chordates.

Chordate Phylum

• Divisions:

  • Urochordates (tunicates)
  • Cephalochordates (amphioxus)
  • Vertebrates (mammals, birds, reptiles, amphibians, fish)

• Characteristics:

  • Notochord: A flexible rod-shaped structure derived from mesoderm, found in the embryo of all chordates.
  • Pharyngeal slits: "U"-shaped openings in the pharynx that connect to the exterior via gill slits, allowing water to pass through. The number can range from a few to over 100.
  • Dorsal nerve cord: A bundle of nerve fibers derived from ectoderm, running parallel to the notochord. In vertebrates, it corresponds to the spinal cord, and its anterior thickening forms the brain.
  • Post-anal tail: An extension of the body beyond the anus, aiding in larval or adult swimming.

Vertebrate Subphylum

• Characteristics:

  • High complexity.
  • Chordate characteristics present at some point in their life cycle, often during the embryonic stage.
  • Bilateral symmetry (with paired limbs in less advanced forms).
  • Advanced nervous system.
  • Endoskeleton:
    • Axial skeleton:
      • Cranium: Protects the brain.
      • Vertebral column: Protects the spinal cord, replacing the notochord (partially or entirely in some vertebrates).
    • Appendicular skeleton:
      • Pectoral and pelvic girdles.
      • Limbs.

• Endoskeleton characteristics:

  • Internal, but may have mineralized external structures (scales, plates, osteoderms, shields, etc.).
  • Can be bony or cartilaginous, or a combination of both.
  • Multiple embryonic origins.
  • Notochord may persist in some jawless vertebrates (jawless fish).

Agnatha and Gnathostomata

• Agnatha: Jawless vertebrates (e.g., lampreys, hagfish)
• Gnathostomata: Jawed vertebrates (e.g., fish, amphibians, reptiles, birds, mammals)

Other Vertebrates

• Conodonts: Cambrian-Triassic marine organisms, primarily known from isolated elements.
• Placoderms: Armored jawed fish of the Ordovician to Devonian periods.
• Chondrichthyes: Cartilaginous fish (e.g., sharks, rays, skates).
  • Continuously growing teeth, replacing lost ones.
  • Helicoprion: A spiral-toothed cartilaginous fish.
• Osteichthyes: Bony fish.
  • Actinopterygii (ray-finned fishes): Most diverse group of bony fishes.
  • Sarcopterygii (lobe-finned fishes): Gave rise to tetrapods.
• Tetrapods: Four-limbed vertebrates.
  • Amphibia: Include salamanders, frogs, toads etc.
  • Amniotes: Include reptiles, birds, and mammals.
  • Amniotes:
    • Syapsids: Reptiles with skulls with a single temporal fenestra.
    • Diapsids: Reptiles with skulls with two temporal fenestras.
      • Lepidosauria (lizards, snakes etc.)
      • Archosauria (crocodiles, dinosaurs, birds)
    • Anàpsids: Reptiles with skulls with no temporal fenestras.
• Mesozoic Reptiles:
  • Plesiosaurs and pliosaurs
  • Ichthyosaurs and Mosasaurs
  • Pterosauria (Pterosaurs)
• Dinosaures:
  • Saurischians: Have a forward-facing pubis.
  • Ornithischians: Have a backward-facing pubis
    • Thyreophora (e.g., Stegosaurus, Ankylosaurus)
    • Ornithopoda (e.g., Iguanodon, Hypsilophodon)
    • Marginocephalia (e.g., Triceratops, Pachycephalosaurus)
• Mammals:
  • Monotremes (e.g., platypuses, echidnas)
  • Marsupials (e.g., kangaroos, koalas, opossums)
  • Placentals (e.g., primates, carnivores, ungulates)
• Evolutionary history of humans: Includes the different stages of hominin evolution and species, including Ardipithecus, Australopithecus, and Homo. This is not a linear progression, and many lines of hominins died out without producing modern humans.

Aquesta prova explora les diferències entre protostomes i deuterostomes, incloent-hi exemples de cada un. També s'examinen les divisions del fílum dels cordats i les seves característiques distintives com el notocord i les fissures branquials.