Animals Animal Form & Function By far, most diversity of bauplane (body forms). And most variations within bauplane. Animals are Animated “ANIMAL” ≠ MAMMAL — Fascinating Behaviors Animal Cells • Eukaryotic • No cell wall No plastids No central vacuole • Multicellular: – extensive specialization & differentiation – unique cell-cell junctions Heyer 1 Animals Animals Blastulation & Gastrulation • Motile • Early embryonic development in animals 3 In most animals, cleavage results in the formation of a multicellular stage called a 1 The zygote of an animal • Highly differentiated blastula. The blastula of many animals is a undergoes a succession of mitotic tissues cell divisions called cleavage. hollow ball of cells. Blastocoel • Intercellular junctions Cleavage Cleavage – tissue-specific cadherins 6 The endoderm of the archenteron develops into Eight-cell stage Blastula Cross section Zygote • Extracellular protein the the animal’s of blastula fibers digestive tract. Blastocoel Endoderm – collagen 5 The blind pouch formed by gastrulation, called Ectoderm • Diploid life cycle the archenteron, opens to the outside Gastrula Gastrulation via the blastopore. Blastopore 4 Most animals also undergo gastrulation, a • Blastula/gastrula rearrangement of the embryo in which one end of the embryo folds inward, expands, and eventually fills the embryo blastocoel, producing layers of embryonic tissues: the Figure 32.2 ectoderm (outer layer) and the endoderm (inner layer). Primary embryonic germ layers Primary embryonic germ layers • Diploblastic: two germ layers • Triploblastic: three germ layers – Ectoderm: develops into epidermal & neural tissues – Ectoderm: develops into epidermal & neural tissues – Endoderm: develops into feeding tissues – Endoderm: develops into gut & accessory organs – Blastocoel: becomes filled with acellular mesoglia – Mesoderm — displaces blastocoel: develops into muscle, endoskeleton, & connective tissues Blastocoel Examples: Examples: Endoderm Porifera & Cnidaria everything else Archenteron Ectoderm Blastopore Mesoderm Blastopore Figure 32.9b Body Symmetry Body Symmetry • Asymmetry • Asymmetry – Determined by environmental constraints — Encrusting – Determined by environmental constraints — Encrusting Bilateral symmetry. A bilateral animal, such as • Radial symmetry • Radial symmetry a lobster (phylum Arthropoda), has a left side and a right side. Only one imaginary cut divides Figure 32.7a • Bilateral symmetry the animal into mirror-image halves. Radial symmetry. The parts of a radial animal, such as a sea anemone (phylum Cnidaria), radiate from the center. Any imaginary slice through the central axis divides the Figure 32.7b animal into mirror images. • Body orientation has two recognizable lateral sides (right/left); anterior (front); • Body orientation has two recognizable sides: posterior (rear); dorsal (back); & ventral (belly) dimensions. oral (with mouth) & aboral (opposite side from mouth) • Generally accompanied by cephalization: localization of sensory and central nervous centers to the anterior (head) Heyer 2 Animals Variations in Gastrulation: Protostome development Deuterostome development (examples: molluscs, (examples: echinoderms, annelids) chordates) Digestive tract (a) Cleavage Eight-cell stage Eight-cell stage • Gastrovascular cavity (blind gut) – Blastopore remains only orifice to gut • Protostome (“mouth first”) development Spiral and determinate Radial and indeterminate – The blastopore becomes the mouth (b) Coelom Coelom – Secondary invagination to form anus formation • Deuterostome (“mouth second”) development Archenteron – The blastopore becomes the anus Coelom – Secondary invagination to form mouth Mesoderm Blastopore Blastopore Mesoderm Solid masses of mesoderm Folds of archenteron split and form coelom. form coelom. Anus Mouth (c) Fate of the Anus Mouth blastopore Digestive tube Gastrovascular Digestive tube Cavity Key Ectoderm Mouth Mouth Anus Mesoderm Mouth Anus Mouth develops Mouth develops Anus develops Endoderm Mouth develops from blastopore. Anus develops from blastopore. from blastopore. from blastopore. from blastopore. Figure 32.10 Organ Systems Circulatory & Respiratory Systems External environment Mouth Food CO2 O2 Animal body Respiratory m Blood system µ Mouth 50 0.5 cm Cells Heart Gastrovascular cavity Nutrients Circulatory 10 µm Diffusion system Digestive Interstitial fluid system The lining of the small intestine, a diges- Excretory Diffusion tive organ, is elaborated with fingerlike system projections that expand the surface area for nutrient absorption (cross-section, SEM). Anus Unabsorbed Metabolic waste matter (feces) products (urine) Figure 40.3b (b) Two cell layers Figure 40.4 Circulatory Systems Uncertain Systematics Cnidaria Chordata Rotifera Annelida Mollusca Silicarea Calcarea Nemertea Phoronida Rotifera Nematoda Porifera Cnidaria Ectoprocta Arthropoda Ctenophora Annelida Mollusca Phoronida Chordata Brachiopoda Nemertea • Ciliated Body Cavity Nematoda Ctenophora Ectoprocta Arthropoda Echinodermata Platyhelminthes Brachiopoda Echinodermata Platyhelminthes • Open Circulatory System “Radiata” “Porifera” Deuterostomia Lophotrochozoa Ecdysozoa “Radiata” Deuterostomia Protostomia • Closed Circulatory System Bilateria Bilateria Figure 32.10 Eumetazoa Figure 32.11 Eumetazoa Cladogram based on Cladogram based on certain morphological certain molecular and Metazoa Metazoa and developmental other developmental Hypothetical Hypothetical characters characters Ancestor Ancestor • No fossil record — all phyla appear simultaneously (“Cambrian explosion”) Hemocoel • Morphological, embryological, and molecular characters all yield contradictory patterns Heyer 3 Animals I Phylum Porifera: Sponges Phylum Porifera: Sponges • Embryonic development: – Diploblastic – Radial symmetry ® may become asymmetrical – No coelom • acellular mesoglia between endoderm and ectoderm – Gut ® filter chamber (spongocoel) • intracellular digestion – Flagellated larvae – Circulatory systems: – Flagellated* spongocoel – Cell-mediated: amoebocytes • Special features: – Choanocytes – Amoebocytes – Spicules – *Flagellated tissue Phylum Porifera: Sponges Phylum Cnidaria: Polyp & Medusa • ↑ body size → ↑↑ surface area to balance ↑↑ body mass Phylum Cnidaria: Polyp Phylum Cnidaria: Polyp & Medusa • Embryonic development: – Diploblastic – Radial symmetry – No coelom • acellular mesoglia – Ciliated / contractile gastrovascular cavity – Ciliated planula larvae • Special features: – Polyps & medusas – Ciliated myoepithelia – Cnidocytes w/ nematocysts Heyer 4 Animals I Phylum Cnidaria: Life Cycle Phylum Cnidaria Jellyfish Anemone medusae polyps Phylum Cnidaria: Cnidocytes Phylum Cnidaria: Corals polyps w/symbiotic zooxanthellae Specialized nematocysts: entangling, adhesive, penetrating, venomous (photosynthetic protists) Box jelly nematocysts: http://www.youtube.com/watch?v=-Tp38DUjUnM&feature=relateD Phylum Annelida: Segmented Worms • Embryonic development: – Triploblastic – Bilateral symmetry w/ cephalization – Closed vascular circulatory system – Protostome – Eucoelomate – Lophotrochozoa • Special features: – Segmentation – Hydrostatic skeleton Heyer 5.