E2.AnimalsF10 - Animals Morphogenesis Morphogenesis& Differentiation • In plants by differential growth • In animals by both growth& cell

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Unformatted text preview: Animals Morphogenesis Morphogenesis & Differentiation • In plants, by differential growth • In animals, by both growth & cell migration Cell movement Zygote (fertilized egg) Eight cells Gut Blastula Gastrula Adult animal (cross section) (cross section) (sea star) Cell division Morphogenesis Observable cell differentiation Seed leaves Shoot apical meristem • Patterns of Development Figure 21.4 – Cell proliferation – Cell migration – Cell differentiation 1 • Binding of sperm to egg 2 sea urchin (echinoderm), a model organism Acrosomal reaction: plasma membrane depolarization (fast block to polyspermy) 3 4 Seconds Creation of form - directed by genes Root apical meristem Embryo Plant inside seed Two cells post-fertilization events Morphogenesis • Zygote (fertilized egg) 6 8 10 Increased intracellular calcium level 20 Cortical reaction begins (slow block to polyspermy) 30 Sperm head 40 50 1 Formation of fertilization envelope complete EGG CYTOPLASM 2 Minutes 3 4 5 Increased intracellular pH Increased protein synthesis 10 20 Fusion of egg and sperm nuclei complete 30 40 Onset of DNA synthesis 60 First cell division 90 Figure 47.5 Blastulation & Gastrulation Spiral vs. Radial Cleavage • Early embryonic development in animals 3 In most animals, cleavage results in blastulation : 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 . • Protostomes: mouth first – most invertebrates – spiral cleavage – determinate • Deuterostomes: mouth second – echinoderms, protochordates & vertebrates – radial cleavage – indeterminate Blastocoel Cleavage 6 The endoderm of the archenteron develops into the the animal’s digestive tract. Blastulation Zygote Eight-cell stage Blastula Cross section of blastula Blastocoel Endoderm Gastrulation forms a blind pouch, called the archenteron , Gastrula that opens to the outside via the Blastopore blastopore . 5 Figure 32.2 Heyer Cleavage Ectoderm 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). 1 Animals Blastulation —Frog Blastulation — Sea Urchin • Cleavage partitions the cytoplasm of one large cell into many smaller cells called blastomeres (a) Fertilized egg. Shown here is the zygote shortly before the first cleavage division, surrounded by the fertilization envelope. The nucleus is visible in the center. (b) (c) Morula. After further cleavage divisions, the embryo is a multicellular ball that is still surrounded by the fertilization envelope. The blastocoel cavity has begun to form. Four-cell stage. Remnants of the mitotic spindle can be seen between the two cells that have just completed the second cleavage division. (d) • Large yolk content necessitates asymmetrical blastulation Blastula. A single layer of cells surrounds a large blastocoel cavity. Although not visible here, the fertilization envelope is still present; the embryo will soon hatch from it and begin swimming. Figure 47.7 Another way — asymmetric blastulation in many vertebrates • Large, yolk-rich eggs • Cleavage forms the blastoderm . • Separation of the epiblast from the hypoblast forms the blastocoel. Fertilized egg Gastrulation — Sea Urchin Figure 47.10 Disk of cytoplasm 1 Zygote. Most of the cell’s volume is yolk, with a small disk of cytoplasm located at the animal pole. 2 Four-cell stage. 3 Blastoderm. The many cleavage divisions produce the blastoderm, a mass of cells that rests on top of the yolk mass. Blastocoel BLASTODERM YOLK MASS Epiblast Hypoblast Cutaway view of the blastoderm. The cells of the blastoderm are arranged in two layers, the epiblast and hypoblast, that enclose a fluidfilled cavity, the blastocoel. Gastrulation — Chick • Instead of blastopore, groove (primitive streak) forms in blastoderm. • All three germ layers form from infolding epiblast. epiblast. Gastrulation — Chick • Organogenesis from germ layers. Eye Epiblast Forebrain Neural tube Notochord Somite Heart Coelom Future ectoderm Primitive streak Archenteron Endoderm Mesoderm Lateral fold Blood vessels Ectoderm Yolk stalk Migrating cells (mesoderm) Endoderm Hypoblast YOLK Figure 47.13 Heyer Somites Yolk sac Form extraembryonic membranes YOLK (a) Early organogenesis. The archenteron forms when lateral folds pinch the embryo away from the yolk. Neural tube (b) Late organogenesis. 56 hours old chick embryo, about 2–3 mm long (LM). Figure 47.15 2 Animals Primary embryonic germ layers Triploblastic gastrulation forms three germ layers • Triploblastic: three germ layers – Ectoderm : develops into epidermal & neural tissues – Endoderm: develops into gut & accessory organs – Mesoderm — displaces blastocoel: develops into muscle, endoskeleton, & connective tissues Archenteron ECTODERM • Epidermis of skin and its derivatives (including sweat glands, hair follicles) • Epithelial lining of mouth and rectum • Sense receptors in epidermis • Cornea and lens of eye • Nervous system • Adrenal medulla • Tooth enamel • Epithelium or pineal and pituitary glands MESODERM • Notochord • Endoskeletal system • Muscular system • Muscular layer of stomach, intestine, etc. • Excretory system • Circulatory and lymphatic systems • Reproductive system (except germ cells) • Dermis of skin • Lining of body cavity • Adrenal cortex ENDODERM • Epithelial lining of digestive tract • Epithelial lining of respiratory system • Lining of urethra, urinary bladder, and reproductive system • Liver • Pancreas • Thymus • Thyroid and parathyroid glands Figure 47.16 Mesoderm Blastopore Figure 32.9b Triploblastic Animal Tissues • Typical mammalian body is composed of ~50,000,000,000,000 cells • Typical vertebrate body is composed of >100 specialized types of cells (tissue types) – Grouped into four major tissue types: • Epithelial • Connective • Muscle • Nervous Connective Tissue • Cells are suspended in an extracellular matrix. – The matrix is often largely composed of collagen fibers. • Derived from mesoderm. Heyer Epithelial Tissue • Continuous sheet or layers of cells with direct cellcell junctions • All three germ layers start as epithelia, so epithelial tissues may derive from any germ layer. Muscle Tissue • Specialized for contraction. • Derived from mesoderm. • Diploblastic animals have myo-epithelia for contraction. 3 Animals Nervous Tissue Bauplan: Ger. “Life Plan” (pl: baupläne) • Specialized to conduct electrochemical nerve impulses. The arrangement, pattern, and development of tissues, organs, and systems unique to a particular type of organism. • Derived from ectoderm. Coelom Larval Development Protostomal development occurs in two distinct animal groups Usually with a distinct larval stage called a trochophore Apical tuft of cilia All stages have a chitinous cuticle Growth requires ecdysis (molting) • Acoelomate : no body cavity • Pseudocoelomate: cavity between endoderm & mesoderm Mouth Anus trochophore larva Figure 32.13 Phylum Platyhelminthyes: “Flat Worms” Tissuefilled region (from mesoderm) Digestive tract (from endoderm) Pseudocoelomate. nematode worm Pseudocoelom Figure 32.8 Body covering (from ectoderm) Muscle layer (from mesoderm) Digestive tract (from ectoderm) • Eucoelomate: cavity within (a) mesoderm Coelomate. annelid worm Coelom ecdysis Figure 32.12 Body covering (from ectoderm) (b) • Ecdysozoa: have no ciliated tissues – – Acoelomate. flatworms – Formation of body cavities allows movement of organs within the body, esp. gut expansion & motility • Lophotrochozoa: have ciliated larval stages – (c) Digestive tract (from endoderm) Body covering (from ectoderm) Tissue layer lining coelom and suspending internal organs (from mesoderm) Bilateral symmetry with cephalization • Embryonic development: – Triploblastic – Bilateral symmetry w/ cephalization • Turbellarian flatworm – No circulatory system – Gastrovascular cavity – Acoelomate • Special features: – Dorso-ventrally flattened Heyer 4 Animals Phylum Platyhelminthyes • ~10,000 named spp.; >half parasitic – Turbellarians: • aquatic free living/predatory – Trematodes (flukes) & Cestodes (tapeworms): • endoparasites Phylum Nematoda (Nemata): “Thread-like”: Round Worms Phylum Nematoda • Embryonic development: – Triploblastic – Bilateral symmetry w/ cephalization – No circulatory system – Protostome – Pseudocoelomate – Ecdysozoa • Special features: – Most ubiquitous animal on earth! Phylum Annelida: Segmented Worms • Embryonic development: – Triploblastic – Bilateral symmetry w/ cephalization – Closed circulatory system – Protostome – Eucoelomate – Lophotrochozoa • Special features: – Segmentation – Hydrostatic skeleton Heyer 5 Animals Annelida Annelida • 2 Classes • 2 Classes – Polychaeta – bristle worms ~12,000 spp. – Clitellata – earthworms & leeches ~ 5,000 spp. anus – Polychaeta – bristle worms ~12,000 spp. – Clitellata – earthworms & leeches ~ 5,000 spp. •Head • Prostomium [“before mouth”] • Peristomium [“around mouth”] •Metameres (segments) •Pygidium • Growth zone mouth Phylum Mollusca “soft body” Worm locomotion • Embryonic development: – Triploblastic – Bilateral symmetry w/ cephalization - flatworms & larval annelids • Bivalves lack cephalization • Gastropods have torsion Requires coordination of longitudinal + circular muscles - annelids – Eucoelomate - reduced – Protostome – Lophotrochozoa – Open circulatory system [except cephalopods] Only longitudinal muscles - roundworms & large flatworms • Special features: – Muscular foot, visceral mass, and mantle, usually w/ shell – Mantle cavity w/ gills – Radula Odontophore & Radula Molluscan body plan Visceral mass Coelom Intestine Gonads Mantle Stomach Mantle cavity Shell Radula Mouth Anus The nervous system consists of a nerve ring around the esophagus, from which nerve cords extend. Gill Radula. Foot Nerve cords Esophagus Mouth Figure 33.16 Heyer 6 Animals Phylum Mollusca Gastropod molluscs 2nd most diverse phylum: >100,000 spp. • The most distinctive characteristic of this class is a developmental process known as torsion, which causes the animal’s anus and mantle to end up above its head • Class Polyplacophora: chitons • Class Gastropoda: snails & slugs Mantle cavity Stomach Intestine Anus • Class Cephalopoda: octopus & squid Mouth • Class Bivalvia: clams & mussels Figure 33.19 Torsion in Gastropods Cephalopods •In early development, left side of body grows faster than right side. •Results in 180° twist of visceral mass relative to head-foot axis. •Relocates anus & mantle cavity behind head: ↑ventilation of gills & elimination of feces ↑ retraction of head into shell aperture Bivalve molluscs • The mantle cavity of a bivalve contains gills that are used for feeding as well as gas exchange Mantle Hinge area Gut Movement of the Ventilating Currents & Food Capture Coelom Heart Adductor muscle Shell Mouth Anus Excurrent siphon Palp Foot Figure 33.21 Heyer Mantle cavity Gill Water flow Incurrent siphon 7 Animals Phylum Arthropoda: bugs Arthropods • Segmented body covered by an exoskelton • Numerous specialized jointed appendages • Embryonic development: – Triploblastic Cephalothorax – Bilateral symmetry w/ cephalization – Eucoelomate Antennae (sensory reception) – Protostome Head Abdomen Thorax – Ecdysozoa – Open circulatory system Swimming appendages • Special features: – Segmentation → tagmata – Chitinous exoskeleton / ecdysis Walking legs – Paired jointed appendages Pincer (defense) Mouthparts (feeding) Figure 33.29 Phylum Echinodermata Planktonic crustaceans • Embryonic development: • Esp. copepods & euphausids (krill) • The most abundant animals on earth – Triploblastic – Pentamerous radial symmetry – Eucoelomate — reduced/replaced by hydrocoel – Deuterostome – No circulatory system • Special features: – Water vascular system Most copepods are only 1–2 mm in length. But the total biomass of all the oceans’ copepods exceed by far the total mass of all the oceans’ whales! – Tube feet & pedicellaria Figure 33.38b Planktonic crustaceans known as krill are consumed in vast quantities by whales. Echinoderm body plan • Pentamerous (5-part) radial symmetry • Unique to echinoderms is a water vascular system — A network of hydraulic canals branching into tube feet that function in locomotion, feeding, and gas exchange A short digestive tract runs from the mouth on the bottom of the central disk to the anus on top of the disk. Central disk. The central disk has a nerve ring and nerve cords radiating from the ring into the arms. Digestive glands secrete digestive juices and aid in the absorption and storage of nutrients. Radial canal. The water vascular system consists of a ring canal in the central disk and five radial canals, each running in a groove down the entire length of an arm. Figure 33.39 Heyer Stomach Anus Spine Gills Ring canal Gonads Ampulla Podium Tube feet Radial nerve – Calcareous endoskeleton Phylum Echinodermata • Class Asteroidea: sea stars • Class Ophiuroidea: brittle stars The surface of a sea star is covered by spines that help defend against predators, as well as by small gills that provide gas exchange. Madreporite. Water can flow in or out of the water vascular system into the surrounding water through the madreporite. Branching from each radial canal are hundreds of hollow, muscular tube feet filled with fluid. Each tube foot consists of a bulb-like ampulla and suckered podium (foot portion). When the ampulla squeezes, it forces water into the podium and makes it expand. The podium then contacts the substrate. When the muscles in the wall of the podium contract, they force water back into the ampulla, making the podium shorten and bend. • Class Echinoidea: sea urchins • Class Holothuroidea: sea cucumbers 8 Animals Numbers of species Arthropoda Mollusca Chordata Platyhelminthes Nematoda Annelida Porifera Echinodermata Other Sarcomastigophora Apicomplex Ciliophora Kingdom Animalia ~35 phyla / disputed clades Diploblastic Porifera Triploblastic Acoelomate Platyhelminthes Triploblastic Pseudocoelomate Nematoda Triploblastic Eucoelomate Annelida Cnidaria Mollusca Arthropoda Echinodermata Chordata Mesozoa * Porifera Radiata * Cnidaria Lophotrochozoa Ecdysozoa Deuterostomia Platyhelminthes Nematoda Echinodermata Annelida Arthropoda Chordata Mollusca * Probably not true monophyletic clades Heyer 9 ...
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This note was uploaded on 09/02/2011 for the course BIOL 6a taught by Professor Staff during the Fall '10 term at DeAnza College.

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