2-Vertebrate Structure and Development (Part I) VERTEBRATE DIVERSITY CHORDATE PHYLOGENY AND HOMOLOGY DEUTEROSTOME DEVELOPMENT CHORDATE BODY PLAN
How do they do that????
DIVERSITY Pough et al. 2005, p. 12 Mammalia Agnatha Chondrichthyes Aves Reptilia Osteichthyes Amphibia
HOMOLOGY Q: What does the presence of a single vertebrate anatomical plan tell us? Reptilia Agnatha Aves Chondrichthyes Mammalia Osteichthyes Amphibia Q: If there is a single anatomical plan, why do vertebrates look so different? code: 9514
Q: How can we explain the use of different (non-homologous) organs for the same function? ANALOGY
Q: How can we explain similar (but not identical) traits and lifestyles in animals that are not closely related? CONVERGENCE
Q: How can we explain evolutionary novelties that are NOT present in all vertebrates? EXAPTATION ADAPTATION
Because living things share a common ancestry, their similarities (and inferred relationships) are hierarchical. time Phylum Subphylum Class Order Family Genus Species
Vertebrates are members of the Phylum Chordata Q: How might we predict what the ancestors of Phylum Chordata looked like? non-vertebrate chordates (Subphyla) vertebrate chordates (Subphylum) notochord perforated pharynx dorsal tubular nerve cord postanal tail endostyle / thyroid
Q: How are vertebrate chordates different from non-vertebrate chordates? non-vertebrate chordates (Subphyla) vertebrate chordates (Subphylum) all chordates have: vertebrate chordates have: and also have: perforated pharynx notochord perforated pharynx notochord vertebrae brain dorsal tubular nerve cord postanal tail dorsal tubular nerve cord postanal tail cranium neural crest endostyle / thyroid endostyle / thyroid
Q: In what sequence did these traits evolve? Nonvertebrate chordates Vertebrate chordates agnathans amphioxus osteichthyes amphibia reptiles mammals birds
Q: In what sequence did these traits evolve? Nonvertebrate chordates Vertebrate chordates agnathans amphioxus osteichthyes amphibia reptiles mammals birds vertebrae, cranium, brain, neural crest perforated pharynx, dorsal tubular nerve cord, notochord
Nonvertebrate chordates Vertebrate chordates Agnatha Gnathostomes vertebrae, cranium, brain, neural crest perforated pharynx, dorsal tubular nerve cord, notochord jaws, paired appendages
Nonvertebrate chordates Vertebrate chordates Agnatha Gnathostomes Jawed fish Tetrapods 4 legs, choanae jaws, paired appendages vertebrae, cranium, brain, neural crest perforated pharynx, dorsal tubular nerve cord, notochord
Nonvertebrate chordates Vertebrate chordates Agnatha Gnathostomes Jawed fish Anam. Tetrapods Amniotes 4 legs, choanae jaws, paired appendages vertebrae, cranium, brain, neural crest amnion perforated pharynx, dorsal tubular nerve cord, notochord
Q: how could you use this information to identify which of these vertebrates with convergent adaptations is an amphibian?
Q: What is the relationship of the classes of living vertebrates to each other? vs Haeckel
Given the same ancestral ground plan and the demands of homeostasis, how have different vertebrates adapted to widely different environments?
A single vertebrate body plan all chordates have: vertebrate chordates have: and also have: perforated pharynx notochord perforated pharynx notochord vertebrae brain dorsal tubular nerve cord postanal tail dorsal tubular nerve cord postanal tail cranium neural crest endostyle / thyroid endostyle / thyroid
These are largely developmental characters.... Q2: What can we gain from studying development in a physiology class? code:7677 20
1. Embryology can tell us *how* and *why* we as primate, mammal, amniote, tetrapod, vertebrate, chordates got our shape: - we are tubes within tubes - all our cells come from 3 lines, lines interact to form body 2. Embryology helps explain mechanisms by which evolution creates new forms, including we primate fishes 21
DEUTEROSTOME DEVELOPMENT Q: how does early development differ in protostomes and deuterostomes?
zygote morula blastula Gastrulation: one layer to three Q: What is the fate of the blastopore? http:// worms.zoology.wisc.edu/ frogs/gastxen/wholegas.html
Fate maps of the blastula Major derivatives of each germ layer Q: what is the relationship of the 3 chordate characters to the 3 germ (tissue) layers?
Differentiation of the ectoderm to form the dorsal tubular nerve cord http://www.gastrulation.org/movie13_1.mov
Differentiation of the mesoderm to form somites (paraxial mesoderm), intermediate mesoderm, and lateral plate mesoderm and their many derivatives..including the notochord.
Differentiation of the anterior gut (endoderm) to form the perforated pharynx Q: what is the ancestral function of the perforated pharynx?