Intoranimal lecture 8


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  • Figure 32.2 Early embryonic development in animals.
  • Figure 32.2 Early embryonic development in animals.
  • Figure 32.2 Early embryonic development in animals.
  • Figure 32.3 Three lines of evidence that choanoflagellates are closely related to animals.
  • Figure 32.7 Body symmetry.
  • Figure 32.8 Body cavities of triploblastic animals.
  • Figure 32.9 A comparison of protostome and deuterostome development.
  • Figure 32.10 A view of animal phylogeny based mainly on morphological and developmental comparisons.
  • Figure 32.11 A view of animal phylogeny based mainly on molecular data.
  • Figure 33.2 Review of animal phylogeny.
  • Figure 33.3 Exploring: Invertebrate Diversity
  • Figure 33.3 Exploring: Invertebrate Diversity
  • Figure 33.3 Exploring: Invertebrate Diversity
  • Intoranimal lecture 8

    1. 1. Animal are multicellular, heterotrophic eukaryotes with tissues that develop from embryonic layers (with some exceptions) • Several characteristics, taken together, sufficiently define the group – Heterotrophs – Reproduce sexually, with the diploid stage usually dominating the life cycle – multicellular eukaryotes – lack cell walls – Their bodies are held together by structural proteins such as collagen – Nervous tissue and muscle tissue are unique, defining characteristics of animals – Tissues are group of cells that have a common structure, function or both
    2. 2. Figure 32.2-1 Reproduction and Development Zygote Cleavage Eight-cell stage After a sperm fertilizes an egg, the zygote undergoes rapid cell division called cleavage Cleavage leads to formation of a multicellular, hollow blastula The blastula undergoes gastrulation, forming a gastrula with different layers of embryonic tissues
    3. 3. Figure 32.2-2 Zygote Cleavage Blastocoel Cleavage Eight-cell stage Blastula Cross section of blastula
    4. 4. Figure 32.2-3 Zygote Cleavage Blastocoel Cleavage Eight-cell stage Blastula Cross section of blastula Gastrulation Blastocoel Endoderm Ectoderm Archenteron Cross section of gastrula Blastopore
    5. 5. More Animal Characteristics • Many animals have at least one larval stage i. A larva is sexually immature and morphologically distinct from the adults ii. A juvenile resembles an adult, but is not yet sexually mature • Most animals, and only animals, have Hox genes that regulate the development of body form i. Although the Hox family of genes has been highly conserved, it can produce a wide diversity of animal morphology
    6. 6. Figure 32.3 Individual choanoflagellate Choanoflagellates OTHER EUKARYOTES Sponges Animals Other animals Collar cell (choanocyte)
    7. 7. Animals can be characterized by “body plans” • Symmetry – radial symmetry, with no front and back, or left or right • Radial animals are often sessile or planktonic – Two-sided symmetry is called bilateral symmetry • Bilaterally symmetrical animals have     a dorsal (top) and a vental (bottom) side A right and left side Anterior (head) and posterior (tail) ends Cephalization, the development of a head
    8. 8. Figure 32.7 (a) Radial symmetry (b) Bilateral symmetry
    9. 9. Tissues • Animal body plans also 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 1. Ectotherm is the germ layer covering the embryo’s surface 2. Endoderm is the innermost germ layer and lines the developing digestive tube, called the archenteron 3. Mesoderm lies between the ectoderm and endoderm
    10. 10. Body Cavities • Sponges and a few other groups lack true tissues • Diploblastic animals have ectoderm and endoderm  These include cnidarians and comb jellies • Triploblastic animals also mesoderm; these include all bilaterians  Most triploblastic animals possess a body cavity  A true body cavity is called a coelom and is derived from mesoderm – Coelomates are animals that possess a true coelom • These include flatworms, arthropods, vertebrates and others
    11. 11. Figure 32.8 (a) Coelomate Coelom Digestive tract (from endoderm) Body covering (from ectoderm) Tissue layer lining coelom and suspending internal organs (from mesoderm) (b) Pseudocoelomate Body covering (from ectoderm) Pseudocoelom Digestive tract (from endoderm) Muscle layer (from mesoderm) A pseudocoelom is a body cavity derived from the mesoderm and endoderm (c) Acoelomate Body covering (from ectoderm) Tissuefilled region (from mesoderm) Wall of digestive cavity (from endoderm) Triploblastic animals that lack a body cavity are called acoelomates
    12. 12. Coeloms • The coelom is a cavity entirely surrounded by mesoderm. • A coelom provides a tube-within-a-tube arrangement which has many advantages:  Allows visceral organs to grow independently of the body wall  Fluid-filled coelom acts as a hydrostatic skeleton in some animals (e.g. earthworms)  In mammals, the pericardial, peritoneal, and pleural cavities are formed from the coelom
    13. 13. Protostome and Deuterostome Development • Based on early development, many animals can be categorized as having protostome development or deuterostome development – In protostome development, cleavage is spiral and determinate – In deuterostome development, cleavage is radial and indeterminate – With indeterminate cleavage, each cell in the early stages of cleavage retains the capacity to develop into a complete embryo – Indeterminate cleavage makes possible identical twins, and embryonic stem cells
    14. 14. In some embryos, the daughter blastomeres are either above or to the side of each other. This is said to be radial-type symmetry. In some embryos, the daughter blastomeres are not direclty over or beside each other. They are tilted to the left or right 45 degrees. This latter cleavage symmetry is said to be spiral.
    15. 15. Figure 32.9 Protostome development (examples: molluscs, annelids) (a) Cleavage Deuterostome development (examples: echinoderms, chordates) Eight-cell stage Eight-cell stage Spiral and determinate (b) Coelom formation Radial and indeterminate Coelom Archenteron Coelom Mesoderm Blastopore Blastopore Solid masses of mesoderm split and form coelom. (c) Fate of the blastopore Mesoderm Folds of archenteron form coelom. Anus Mouth Digestive tube Key Ectoderm Mesoderm Endoderm Mouth Mouth develops from blastopore. Anus Anus develops from blastopore.
    16. 16. New views of animal phylogeny are emerging from molecular data • Zoologists recognize about three dozen animal phyla • Phylogenies now combine morphological, molecular, and fossil data • Current debate in animal systematics has led to the development of multiple hypotheses about the relationships among animal groups
    17. 17. Figure 32.10 Porifera Cnidaria Eumetazoa Metazoa ANCESTRAL COLONIAL FLAGELLATE Ctenophora Deuterostomia Protostomia Bilateria One hypothesis of animal phylogeny is based mainly on morphological and developmental comparisons Ectoprocta Brachiopoda Echinodermata Chordata Platyhelminthes Rotifera Mollusca Annelida Arthropoda Nematoda
    18. 18. Figure 32.11 Ctenophora Eumetazoa Metazoa ANCESTRAL COLONIAL FLAGELLATE Porifera Cnidaria Acoela Chordata Platyhelminthes Lophotrochozoa Ecdysozoa Deuterostomia Bilateria One hypothesis of animal phylogeny is based mainly on molecular data Echinodermata Rotifera Ectoprocta Brachiopoda Mollusca Annelida Nematoda Arthropoda
    19. 19. Points of Agreement 1. All animals share a common ancestor 2. Sponges are basal animals 3. Eumetazoa is a clade of animals (eumetazoans) with true tissues 4. Most animal phyla belong to the clade Bilateria, and some are bilarians 5. Chordates and some other phyla belong to the clade Deuterostomia
    20. 20. Progress in Resolving Bilaterian Relationships • The morphology-based tree divides bilaterians into two clades: deuterostomes and protostomes • In contrast, recent molecular studies indicate three bilaterian clades: Deuterostomia, Ecdysozoa, and Lophotrochozoa • Ecdysozoans shed their exoskeletons through a process called ecdysis
    21. 21. Figure 33.2 Invertebrates are animals that lack a backbone that account for 95% of known animal species Porifera ANCESTRAL PROTIST Lophotrochozoa Bilateria Eumetazoa Common ancestor of all animals Cnidaria Ecdysozoa Deuterostomia
    22. 22. Figure 33.3a Porifera (5,500 species) Placozoa (1 species) 0.5 mm A sponge Cnidaria (10,000 species) A placozoan (LM) Ctenophora (100 species) A jelly Acoela (400 species) 1.5 mm Acoel flatworms (LM) A ctenophore, or comb jelly
    23. 23. Figure 33.3b Ectoprocta (4,500 species) Ectoprocts A marine flatworm Acanthocephala (1,100 species) Nemertea (900 species) Rotifera (1,800 species) 0.1 mm Platyhelminthes (20,000 species) Brachiopoda (335 species) A brachiopod A rotifer (LM) Annelida (16,500 species) Cycliophora (1 species) Curved hooks 100 µm An acanthocephalan (LM) Mollusca (93,000 species) A ribbon worm An octopus A cycliophoran (colorized SEM) Lophotrochozoa A marine annelid
    24. 24. Figure 33.3c Loricifera (10 species) Priapula (16 species) Onychophora (110 species) 50 µm A loriciferan (LM) A priapulan An onychophoran Nematoda (25,000 species) Tardigrada (800 species) Arthropoda (1,000,000 species) 100 µm A roundworm (colored SEM) Ecdysozoa Tardigrades (colorized SEM) A scorpion (an arachnid)
    25. 25. • 12.1. Advent of Multicellularity • A. Advantages • 1. Nature’s experiments with larger organisms without cellular differentiation are limited. • 2. Increasing the size of a cell causes problems of exchange; multicellularity avoids surface-to-mass problems. • 3.cell assemblages in sponges are distinct from other metazoans, but molecular evidence shows common ancestry
    26. 26. •B. Form and Function •1. Body openings consist of small incurrent pores or ostia and a few excurrent oscula. •2. Openings are connected by a system of canals; water passes from ostia to osculum. •3. Choanocytes or flagellated collar cells line some of the canals. –a. They keep the current flowing by beating of flagella. –b. They trap and phagocytize food particles passing by. •4. The framework of the sponge is composed of needle-like calcareous or siliceous spicules or organic spongin fibers.
    27. 27. Phylum Porifera A. General Features • Porifera means "pore-bearing"; their sac-like bodies are perforated by many pores. • They are sessile and depend on water currents to bring in food and oxygen and carry away wastes. • Their body is a mass of cells embedded in gelatinous matrix and stiffened by spicules of calcium carbonate or silica and collagen. • They have no organs or tissues; cells are somewhat independent. • Being sessile, they have no nervous or sense organs and have simplest of contractile elements • They are aside from the mainstream of animal evolution and thus they are often called Parazoa • Most of the 5000 species are marine, about 150 are freshwater • Morphology changes with substratum, calmness of water etc… • Sponges are ancient (fossils extend to Cambrian Period
    28. 28. Lophotochozoa • The clade Lophotrochozoa was identified by molecular data • Some develop a lophophore for feeding, others pass through a trochopore larval stage and a few have neither feature • Ex: flatworms, rotifers, ectopracts, brachiopods, molluscs, annelids
    29. 29. Phylum Cnidaria • Two forms – Polyp and medussa  Polyps = sessile  Medusa = free swimming • Cnidocytes = stinging cells on tentacles carnivores • Gastrovascular cavity = central body cavity
    30. 30. Phylum Platyhelminthes • Flatworms • Diffusion replaces body system  Gas exchange takes place across the surface, and protonephridia regulate the osmotic balance • Reproduce asexually by fission • Reproduce sexually by cross fertilization • flukes and tapeworms
    31. 31. Phylum Nematoda • Roundworms • Some are parasitic  Hookworms = drink blood of GI tract  Trichirella found in pig muscle  Filarial roundworms infect lymphatic system
    32. 32. Phylum Annelida • Segmented worms        Closed circulatory system Five pair of hearts Pharynx draws in food Crops store food Gizzard grinds food Intestine absorbs nutrients Rest is passed through the anus
    33. 33. Phylum Arthropoda • Dominant animals wrt numbers – exoskeleton made of chitin – efficient gas exchange – Well developed sensory system – Well developed nervous system – Well developed circulatory system
    34. 34. Phylum Mollusca • Shells of calcium carbonate – mantle lays down the shell • Open circulatory system( except for cephalopods) • Radula tongue made of chitin used to scrape for food • Bivalve named for number of shells • About three-quarters of all living species of molluscs are gastropods
    35. 35. Phylum Echinodermata • Water-vascular system for locomotion, respiration and food acquisition • Lack circulatory system • Have regenerative capabilities