E1.AnimalsF10 - Animals Zoology • Zoology (zoi = animals,...

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Unformatted text preview: Animals Zoology • Zoology (zoi = animals, ology = study of) • Dates to Aristotle's writings about animals based on simple observation. • Grown from descriptive & qualitative to predictive, quantitative field. • Immense body of knowledge = specialization in topics vs. animal groups: Animal Form & Function Why study Animals? • Curiosity • Beauty of nature Animals are Animated — Fascinating Behaviors By far, most diversity of bauplane (body forms). And most variations within bauplane. Charismatic Megafauna Megafauna “Anthropomorphism” Animals as Mirrors “far-sighted ” “playful ” “suspicious ” Heyer 1 Animals “ANIMAL” ≠ MAMMAL Most animals are “cold-blooded” >95% of animal species are invertebrates >83% of all named animal species are arthropods Most diversity of animal body forms are marine invertebrates are marine Animal Cells >50% of ALL species are beetles • • • • Eukaryotic No cell wall No chloroplasts Multicellular: – extensive specialization & differentiation – unique cell-cell junctions Heyer 2 Animals Animals • Multicellular tissues • Motile • Heterotrophic – Usually by ingestion & extracellular digestion • Extracellular protein fibers – Collagen • Diploid life cycle • Blastula/gastrula embryo Animalia: Diploid Life Cycle Blastulation & Gastrulation • Early embryonic development in animals 3 In most animals, cleavage results in the formation of a multicellular stage called a blastula. The blastula of many animals is a hollow ball of cells. 1 The zygote of an animal undergoes a succession of mitotic cell divisions called cleavage. Blastocoel Cleavage Cleavage 6 The endoderm of the archenteron develops into the the animal ’s digestive tract. Zygote Eight-cell stage Blastula Cross section of blastula Blastocoel Endoderm 5 The blind pouch formed by gastrulation, called the archenteron, opens to the outside via the blastopore. Ectoderm Gastrula Blastopore Figure 32.2 Gastrulation 4 Most animals also undergo gastrulation , a rearrangement of the embryo in which one end of the embryo folds inward, expands, and eventually fills the blastocoel, producing layers of embryonic tissues: the 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 – Endoderm : develops into feeding tissues – Blastocoel : becomes filled with acellular mesoglia – Ectoderm : develops into epidermal & neural tissues – Endoderm : develops into gut & accessory organs – Mesoderm — displaces blastocoel : develops into muscle, endoskeleton, & connective tissues Blastocoel Endoderm Examples: Porifera & Cnidaria Examples: everything else Archenteron Ectoderm Blastopore Heyer Mesoderm Blastopore Figure 32.9b 3 Animals Body Symmetry Body Symmetry • Asymmetry • Asymmetry – Determined by environmental constraints — Encrusting • Radial symmetry Figure 32.7a – Determined by environmental constraints — Encrusting • Radial symmetry • Bilateral symmetry Bilateral symmetry. A bilateral animal, such as a lobster (phylum Arthropoda ), has a left side and a right side. Only one imaginary cut divides 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 animal into mirror images. Figure 32.7b • Body orientation has two recognizable sides: oral (with mouth) & aboral (opposite side from mouth) • Body orientation has two recognizable lateral sides (right/left); anterior (front); posterior (rear); dorsal (back); & ventra l (belly) dimensions. • Generally accompanied by cephalization : localization of sensory and central nervous centers to the anterior (head) Circulatory & Respiratory Systems Digestive tract • Gastrovascular cavity (blind gut) – Blastopore remains only orifice to gut • Unnecessary in organisms with bodies only two cells thick • Protostome (“mouth first ”) development – The blastopore becomes the mouth – Secondary invagination to form anus Mouth • Deuterostome (“mouth second ”) development Gastrovascular cavity – The blastopore becomes the anus – Secondary invagination to form mouth Diffusion Mouth Anus Digestive tube Anus Mouth Mouth develops from blastopore Figure 32.9c Diffusion Anus develops from blastopore Figure 40.3b Circulatory & Respiratory Systems Open Versus Closed Circulation External environment Mouth Food CO 2 O2 Respiratory system od Blo 50 µm Animal body 0.5 cm Cells Heart Nutrients Circulatory system 10 µ m Interstitial fluid Digestive system The lining of the small intestine, a digestive organ, is elaborated with fingerlike projections that expand the surface area for nutrient absorption (cross-section, SEM). (b) Two cell layers • Open: “hemolymph” flows in openended vessels • Closed: “blood” stays within vessels Excretory system Anus Unabsorbed matter (feces) Figure 40.4 Heyer Metabolic waste products (urine) Circulatory systems in insect and earthworm 4 Animals Rotifera Arthropoda Nematoda Mollusca Annelida Phylum Porifera: Sponges Nemertea Phoronida Ectoprocta Platyhelminthes Brachiopoda Cnidaria Chordata Echinodermata Silicarea Calcarea Ctenophora Rotifera Nemertea Nematoda Annelida Mollusca Arthropoda Chordata Echinodermata Platyhelminthes Phoronida Ectoprocta Brachiopoda Porifera Cnidaria Ctenophora Uncertain Systematics “Radiata” “Porifera ” “Radiata ” Deuterostomia Deuterostomia Lophotrochozoa Ecdysozoa Protostomia Bilateria Bilateria Eumetazoa Figure 32.10 Figure 32.11 Eumetazoa Metazoa Hypothetical Ancestor • • Cladogram based on certain morphological and developmental characters Metazoa Hypothetical Ancestor Cladogram based on certain molecular and other developmental characters No fossil record — all phyla appear simultaneously (“Cambrian explosion ”) Morphological, embryological, and molecular characters all yield contradictory patterns Phylum Porifera: Sponges • Embryonic development: Phylum Cnidaria: Polyp & Medusa – Diploblastic – Radial symmetry Æ may become asymmetrical – No coelom • acellular mesoglia between endoderm and ectoderm – Gut Æ filter chamber ( spongocoel ) • intracellular digestion – Flagellated larvae – No circulatory system • Special features: – Choanocytes – Amoebocytes – Spicules Phylum Cnidaria: Polyp & Medusa Phylum Cnidaria: Cnidocytes • Embryonic development: – Diploblastic – Radial symmetry – No coelom • acellular mesoglia – Gastrovascular cavity – Ciliated planula larvae – No circulatory system • Special features: – Polyps & medusas – Ciliated myoepithelia – Cnidocytes w/ nematocysts Heyer Specialized nematocysts: entangling, adhesive, penetrating, venomous 5 Animals Phylum Cnidaria: Life Cycle Phylum Cnidaria: Jellyfish medusae Phylum Cnidaria: Anemones polyps Phylum Cnidaria: Corals polyps w/symbiotic zooxanthellae (photosynthetic protists) Phylum Annelida: Segmented Worms • Embryonic development: – Triploblastic – Bilateral symmetry w/ cephalization – Closed circulatory system – Protostome – Eucoelomate – Lophotrochozoa • Special features: – Segmentation – Hydrostatic skeleton Heyer 6 ...
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