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Animal Diversity: Characteristics, Body Plans, and Development

Explore the diversity of animals, from their multicellular and heterotrophic nature to their various body plans and developmental processes. Learn about their unique characteristics, such as the presence of tissues and the role of HOX genes. Discover the different types of symmetry, body cavities, and the distinctions between protostome and deuterostome development.

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Animal Diversity: Characteristics, Body Plans, and Development

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  1. Chapter 32 – Animal Diversity

  2. 32.1 – Animals are multicellular, heterotrophic eukaryotes with tissues that develop from embryonic layers • Animals have the following characteristics: • Multicellular heterotrophs • Most have muscle & nervous tissue • Most reproduce sexually, with a flagellated sperm & a large egg which unite to form a diploid ZYGOTE • The diploid stage dominates the life cycle • 1.3 million living species

  3. Vocab • Zygote • Fertilized egg • Cleavages • Successive mitotic cell divisions without cell growth between cycles • Blastula • Hollow ball of cells surrounding a cavity called the blastocoel

  4. Gastrula • As the blastula is “punched in”, the embryonic tissue layers will form • Ectoderm • The outer tissue layer • Endoderm • The inner tissue layer

  5. Blastopore • Opening into the gastrula • Becomes the mouth in protosomes • Becomes the anus in deuterostomes • Archenteron • Blind pouch formed by gastrulation

  6. Some animals have larvae • Immature form distinct from the adult stage they will undergo metamorphosis • Animals share HOX GENES • Unique family of genes that play important roles in development • Can produce a wide diversity of animal morphology

  7. 32.3 – Animals & Their “Body Plans” • Symmetry • None (sponges) • Radial • Bilateral

  8. Radial occurs in: • Jellyfish • Any cut through the central axis would produce mirror images

  9. Bilateral occurs in • - Lobsters • Humans • Have a right & left side • Single cut would divide the animal into 2 mirror image halves • Dorsal side (back) • Ventral side (belly) • Anterior (head) • Posterior (tail) • Cephalization

  10. Tissues • Animal body plans vary according to the organization of the animal’s tissues • Tissues are collections of specialized cells isolated from other tissues by membranous layers • During development, three germ layers give rise to the tissues and organs of the animal embryo

  11. Ectoderm is the germ layer covering the embryo’s surface • Endoderm is the innermost germ layer and lines the developing digestive tube, called the archenteron • Mesoderm is the middle layer

  12. Diploblastic animals have ectoderm and endoderm • Triploblastic animals also have an intervening mesoderm layer; these include all bilaterians

  13. Body Cavities • Most triploblastic animals possess a body cavity • 3 types: • 1) A coelomate possesses a true body cavity • Derived from mesoderm • Filled with fluid • Separates an animal’s digestive tract from the outer wall • Earthworms

  14. 2) Pseudocoelomate • Triploblastic animals • Cavity formed from mesoderm & endoderm • Roundworms

  15. 3) Acoelomates • No cavities between alimentary canal & outer wall of body • Flatworms

  16. Functions of Body Cavities • 1) Cushion suspended organs • 2) Act as a hydrostatic skeleton • 3) Enable internal organs to grow & move independently

  17. Protostome & Deuterostome Development • 3 major differences: • 1) Cleavage • 2) Coelom formation • 3) Fate of the blastopore

  18. Cleavage: P = begins with spiral, determinate cleavage D = radial, indeterminate cleavage

  19. Coelom Formation: Begins in the gastrula stage P = coelom forms from splits in the mesoderm D = coelom forms from mesodermal outpocketings of the archenteron

  20. Fate of the Blastospore: P = mouth forms from the blastopore D = mouth forms from a secondary opening

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