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Which of these organisms are animals?

Delve into animal early embryonic development from zygote to gastrula, studying blastocoel, cleavage, and three germ layers. Explore the connection between choanoflagellates and animals, fossil records, body symmetry, body cavities, and phylogeny based on morphological and molecular data.

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Which of these organisms are animals?

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  1. Which of these organisms are animals?

  2. Animal Early Embryonic Development Blastocoel Cleavage Endoderm Blastula Ectoderm Archenteron Eight-cell stage Zygote Gastrulation Gastrula Blastocoel Blastopore Cross section of blastula

  3. Three lines of evidence that choanoflagellates protists are closely related to animals Individual choanoflagellate Choanoflagellates OTHER EUKARYOTES Sponges Animals Collar cell (choanocyte) Other animals

  4. Early members of the animal fossil record include the Ediacaran biota, which dates from 565 to 550 million years ago 0.4 cm 1.5 cm (a) Mawsonites spriggi (b) Spriggina floundersi

  5. A Cambrian seascape

  6. Animal Body Symmetry (a) Radial symmetry (b) Bilateral symmetry

  7. Triploblastic Animals Body Cavities Coelom Body covering (from ectoderm) Tissue layer lining coelom and suspending internal organs (from mesoderm) Digestive tract (from endoderm) (a) Coelomate - true body cavity Body covering (from ectoderm) Pseudocoelom Muscle layer (from mesoderm) Digestive tract (from endoderm) (b) Pseudocoelomate Body covering (from ectoderm) Tissue- filled region (from mesoderm) Wall of digestive cavity (from endoderm) (c) Acoelomate - lack a body cavity

  8. Protostome Development molluscs, annelids Deuterostome Development echinoderm, chordates (a) Cleavage Eight-cell stage Eight-cell stage Radial and indeterminate Spiral and determinate Key Coelom Ectoderm (b) Coelom formation Mesoderm Archenteron Endoderm Coelom Blastopore Mesoderm Mesoderm Blastopore Folds of archenteron form coelom. Solid masses of mesoderm split and form coelom. Anus Mouth (c) Fate of the blastopore Digestive tube Mouth Anus Mouth develops from blastopore. Anus develops from blastopore.

  9. “Porifera” Cnidaria ANCESTRAL COLONIAL FLAGELLATE Metazoa Ctenophora Eumetazoa Ectoprocta Brachiopoda Deuterostomia Echinodermata Chordata Bilateria Platyhelminthes Rotifera Protostomia A view of animal phylogeny based mainly on morphological and developmental comparisons Mollusca Annelida Arthropoda Nematoda

  10. Silicea “Porifera” Calcarea ANCESTRAL COLONIAL FLAGELLATE Metazoa Ctenophora Cnidaria Eumetazoa Acoela Echinodermata Deuterostomia Chordata Bilateria Platyhelminthes Rotifera Ectoprocta Lophotrochozoa Brachiopoda A view of animal phylogeny based mainly on molecular data Mollusca Annelida Nematoda Ecdysozoa Arthropoda

  11. Ecdysis - Shedding of Exoskeleton

  12. Lophotrochozoans Characteristics Lophophore Apical tuft of cilia Mouth 100 µm Anus (a) An ectoproct (b) Structure of a trochophore larva

  13. Animal Phylogeny Common ancestor of all animals Sponges (basal animals) Metazoa Ctenophora Eumetazoa Cnidaria True tissues Acoela (basal bilaterians) Deuterostomia Bilateria (most animals) Bilateral summetry Lophotrochozoa Three germ layers Ecdysozoa

  14. You should now be able to: • List the characteristics that combine to define animals. • Summarize key events of the Paleozoic, Mesozoic, and Cenozoic eras. • Distinguish between the following pairs or sets of terms: radial and bilateral symmetry; diploblastic and triploblastic; spiral and radial cleavage; determinate and indeterminate cleavage; acoelomate, pseudocoelomate, and coelomate • Compare the developmental differences between protostomes and deuterostomes.

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