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Chapter 28. The Animal Kingdom: An Introduction to Animal Diversity. Characteristics common to most animals Eukaryotic Multicelleular Heterotrophic Specialized cells. Characteristics common to most animals, cont. Capable of locomotion at some point
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Chapter 28 The Animal Kingdom: An Introduction to Animal Diversity
Characteristics common to most animals • Eukaryotic • Multicelleular • Heterotrophic • Specialized cells
Characteristics common to most animals, cont. • Capable of locomotion at some point • Can respond adaptively to external stimuli • Can reproduce sexually
Characteristics common to most animals, cont. • Sexual reproduction • Sperm and egg unite to form a zygote • Zygote undergoes cleavage • Multiple cell divisions result in a blastula • Blastula undergoes gastrulation
Advantages of life in the ocean • Relatively stable temperatures • Provide buoyancy • Provide food • Fluid and salt balances are most easily maintained in this environment
Disadvantages of life in the ocean • Currents • Other water movements
Disadvantages of life in fresh water • Less constant environment • Less food • Fresh water is hypotonic to tissue fluid, osmoregulation required
Disadvantages of terrestrial life • Potential for dessication • Temperature change • Gametes and embryos must be protected
Animals classified according to body plan • Asymmetrical (most sponges) • Radial (phylum Cnidaria) • Biradial (sea anemones and ctenophores) • Bilateral (most animals)
Animals classified on the basis of tissue development • Diploblastic • Ectoderm • Endoderm • Triploblastic • Ectoderm • Endoderm • Mesoderm
Ectoderm gives rise to • Body covering • Nervous system • Endoderm gives rise to • Gut lining • Digestive organs • Mesoderm gives rise to • Most other body structures
Triploblasts classified according to type of coelom • Acoelomates • Coelomates • Pseudocoelomates • Protostomia • Deuerostomia
Pseudocoelomates were formerly classified as a separate group • Probably not a monophyletic group • Probably evolved through simplification from multiple groups of coelomates
Two main groups of coelomates • Protostomia • Deuterostomia
Protostomia • Spiral cleavage • Cell divisions diagonal to polar axis, therefore spiral arrangement of cells • Deuterostomia • Radial cleavage • Cell divisions parallel or at 90°, therefore cells directly above or below each other
Phylogeny has three major clades of coelomates • Protostomia • Lophotrochozoa • Ecdysozoa • Deuterostomia
Five main animal clades: ParazoaRadiata LophotrochozoaEcdysozoa Deuterostomia
In protostomes, blastophere develops into the mouth • In deuterostomes, the blastophore usually becomes the anus
Protostomes • Lophotrochozoa • Platyhelminthes • Nemerteans • Mollusks • Annelids • Lophophorate phyla • Rotifers
Protozomes, cont. • Ecdysozoa • Nematodes • Arthropods
Deutostomes • Echinoderms • Chordates
Phylum Porifera • Choanocytes: animals with flagellate collar cells • Sole parazoa • Sponge body consists of • Sac with tiny openings • Spongocoel • Osculum • Cells do not form true tissues
A simple sponge cut open to expose its organization. Water drawn through the pores passes through the spongocoel and exits through the osculum. Collar cells trap food particles in the stream of water
Phylum Cnidaria • Radial symmetry • Two tissue layers • Cnidocytes (cells with nematocysts) • Gastrovascular cavity has single opening (both mouth and anus)
Gonothyraea loveni Montastrea cavernosa Chrysaora fuscescens
Phylum Cnidaria, cont. • Irregular, non-directional nerve nets • Nerve nets connect sensory cells with contractile and gland cells • Life cycle of many cnidarians includes • Sessile polyp stage • Free-swimming medusastage
Phylum Cnidaria has three main classes • Hydrozoa • Scyphozoa • Anthozoa
Hydrozoa are usually polyps and may be solitary or colonial • Hydras • Hydroids • Portuguese man-of-war
Scyphozoa are generally medusae • Jellyfish • Anthozoa are polyps and may be solitary or colonial; they differ from hydrozoans in the organization of the gastrovascular cavity • Sea anemones • Corals
Phylum Ctenophora • Comb jellies are fragile, luminescent marine predators • Biradial symmetry • Eight rows of comb-like cilia • Diploblastic • Tentacles with adhesive glue cells