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Copyright © The McGraw­Hill Companies, Inc. Permission required for reproduction or display. CHAPTER 9
Architectural Pattern of an Animal
Animal New Designs for Living n n
Zoologists recognize 34 major phyla of living Zoologists recognize 34 major phyla of living multicellular animals multicellular animals n Survivors of around 100 phyla that n
appeared 600 million years ago during Cambrian explosion n Most important evolutionary event in geological n
history of life n Virtually n
Virtually all major body plans all major body plans were established were established n Major body plans n
n Result of extensive selection n
n Are limiting determinant of future n
Are limiting determinant of future adaptational adaptational variants 9­1 9­2 Copyright © The McGraw­Hill Companies, Inc. Permission required for reproduction or display. Copyright © The McGraw­Hill Companies, Inc. Permission required for reproduction or display. Hierarchical Organization of Animal Complexity n Grades of Organization n
n Unicellular protozoans n
n Simplest Simplest eukaryotic eukaryotic organisms organisms n Protoplasmic Grade of Organization n
n Perform all basic functions with confines of single cell confines of single cell 9­3 9­4 Copyright © The McGraw­Hill Companies, Inc. Permission required for reproduction or display. Copyright © The McGraw­Hill Companies, Inc. Permission required for reproduction or display. Hierarchical Organization of Animal Complexity Hierarchical Organization of Animal Complexity
Hierarchical Organization of Animal Complexity n Metazoa n Tissue Grade of Organization n Cells grouped together n
n Perform common function as a unit (tissue) n
n Multicellular animals n Tissue Tissue­ ­Organ Grade of Organization Organ Grade of Organization n Cells are specialized parts of whole n
(Eumetazoans) organism n Tissues assembled into larger functional n
n Cannot live alone n
units called organs n Cellular Grade of Organization n Chief functional cells of organ n
n Simplest metazoans n
n Parenchyma n
n Cells demonstrate division of labor but are n
n Supportive tissues n
not strongly associated to perform a specific collective function 9­5 n Stroma n
9­6 1
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Copyright © The McGraw­Hill Companies, Inc. Permission required for reproduction or display. Copyright © The McGraw­Hill Companies, Inc. Permission required for reproduction or display. Hierarchical Organization of Animal Complexity Animal Body Plans n Organ n
Organ­ ­System Grade of Organization System Grade of Organization n Organs work together to perform a n Animal Symmetry n
n Symmetry n
common function n Highest level Highest level of organization of organization n Associated with Associated with most animal phyla most animal phyla n Correspondence of size and shape of parts on opposite sides of a median plane n Spherical symmetry n
n Any plane passing through center divides body n
into mirrored halves n Best suited for floating and rolling n
n Found chiefly among some unicellular forms n
n Rare in animals n
9­7 9­8 Copyright © The McGraw­Hill Companies, Inc. Permission required for reproduction or display. Copyright © The McGraw­Hill Companies, Inc. Permission required for reproduction or display. Animal Body Plans n Radial symmetry n
n Body divided into similar halves by more than n
2 planes passing through longitudinal axis n Biradial symmetry n
n Variant form radial symmetry n
n Have part that is single or paired rather n
than radial n Only 2 planes passing through n
longitudinal axis produces mirrored halves n Usually sessile, freely floating, or weakly n
swimming animals n No anterior or posterior end n
n Can interact with environment in all directions n
9­9 9­10 Copyright © The McGraw­Hill Companies, Inc. Permission required for reproduction or display. Copyright © The McGraw­Hill Companies, Inc. Permission required for reproduction or display. Animal Body Plans n Bilateral Symmetry n
n Organism can be divided along a sagittal plane n
into two mirror portions into two mirror portions n Right and left halves n
n Much better fitted for directional (forward) n
movement n Associated with n
Associated with cephalization cephalization n Differentiation of a n
Differentiation of a head region head region with with concentration of nervous tissue and sense organs n Advantageous to an animal moving through its n
environment head first n Always accompanied by differentiation along n
an anteroposterior axis 9­11 9­12
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n n
Copyright © The McGraw­Hill Companies, Inc. Permission required for reproduction or display. Copyright © The McGraw­Hill Companies, Inc. Permission required for reproduction or display. Animal Body Plans Animal Body Plans Regions of bilaterally symmetrical Regions of bilaterally symmetrical animals animals n Distal n
Anterior n Head end n
n Posterior n
n Tail end n
n Dorsal n
n Back side n
n Ventral n
n Front or belly side n
n Medial n
n Midline of body n
n Lateral n
n Sides n
n Parts farther from the middle of body n
n n
9­13 Proximal n n
Frontal plane (coronal plane) n Parts are nearer the middle of body n
n Divides bilateral body into dorsal and ventral n
halves n n
Sagittal plane n n
Transverse plane (cross section) n Divides body into right and left halves n
n Divides body into anterior and posterior n
portions 9­14 Copyright © The McGraw­Hill Companies, Inc. Permission required for reproduction or display. Copyright © The McGraw­Hill Companies, Inc. Permission required for reproduction or display. Body Cavities and Germ Layers Body Cavities and Germ Layers n Body cavity n
n Other animal phyla n
n Sponges n
n Acoelomate: n Development proceeds from Development proceeds from blastula to blastula to gastrula n Invagination of surface cells form the archenteron or primitive gut archenteron n Opening to archenteron is the blastocoel n Becomes the Becomes the mouth or the anus mouth or the anus n Gut is lined by Gut is lined by endoderm endoderm n Outer layer of cells is Outer layer of cells is ectoderm ectoderm no body cavity n In sponges n After blastula formation, cells reorganize to form adult body n Blastula has Blastula has no external opening no external opening n No gut forms 9­15 9­16 Copyright © The McGraw­Hill Companies, Inc. Permission required for reproduction or display. Copyright © The McGraw­Hill Companies, Inc. Permission required for reproduction or display. Body Cavities and Germ Layers Body Cavities and Germ Layers
Body Cavities and Germ Layers n Embryo now has Embryo now has 2 cavities 2 cavities n In n
In Protostomes Protostomes n Gut and blastocoel n Mesoderm forms as endodermal cells near n
blastopore migrate into the blastocoel n Blastocoel Blastocoel persists in some animals n In others, becomes filled with a 3 rd n Three body plans are possible n
germ layer, mesoderm germ layer, mesoderm n Cells forming mesoderm n Derived from endoderm n 2 mechanisms of formation 9­17 n n
n Acoelomate plan n Mesodermal cells completely fill the blastocoel n Gut Gut is only body cavity is only body cavity 9­18 3
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Copyright © The McGraw­Hill Companies, Inc. Permission required for reproduction or display. Copyright © The McGraw­Hill Companies, Inc. Permission required for reproduction or display. Body Cavities and Germ Layers Body Cavities and Germ Layers n Pseudocoelomate Pseudocoelomate plan n Schizocoelous plan n Mesodermal Mesodermal cells line the outer edge n Mesodermal cells fill blastocoel of the blastocoel of the blastocoel n 2 body cavities formed n Persistent Persistent blastocoel blastocoel (pseudocoelom ( pseudocoelom) and a ) and a gut cavity gut cavity n Pseudocoelom n
Pseudocoelom is a false body cavity is a false body cavity (only partially lined with mesoderm) n Mesoderm Mesoderm splits 9­19 n The space is called a The space is called a coelom coelom n True body cavity True body cavity (completely lined (completely lined by mesoderm) n 2 body cavities formed n Gut and coelom 9­20 Copyright © The McGraw­Hill Companies, Inc. Permission required for reproduction or display. Copyright © The McGraw­Hill Companies, Inc. Permission required for reproduction or display. Body Cavities and Germ Layers n In Deuterostomes n
n Mesoderm forms by an n
Mesoderm forms by an enterocoelous plan enterocoelous plan n Cells from central gut lining form pouches n Pouches expand into blastocoel n Wall forms n
Wall forms mesodermal ring mesodermal ring n Pouches enclose a space, n
Pouches enclose a space, coleom coleom n Pouches pinch off from gut lining n
n Coelom completely fills blastocoel n
n 2 body cavities form n
n Gut and coelom n
9­21 9­22 Copyright © The McGraw­Hill Companies, Inc. Permission required for reproduction or display. Copyright © The McGraw­Hill Companies, Inc. Permission required for reproduction or display. Developmental Origins in Triploblasts Body Plans n n
Triploblastic animals follow one of several Triploblastic animals follow one of several major developmental pathways n Most common pathways are by n
Most common pathways are by spiral or spiral or radial cleavage n Radial cleavage n Typically n
Typically accompanied by 3 traits accompanied by 3 traits n Blastopore becomes the anus and new n
opening becomes the mouth n Coelom formation is by enterocoely n
n Cleavage is regulative n
n Animals with these features called n
deuterostomes
deuterostomes 9­23 9­24 4
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Copyright © The McGraw­Hill Companies, Inc. Permission required for reproduction or display. Copyright © The McGraw­Hill Companies, Inc. Permission required for reproduction or display. Developmental Origins in Triploblasts Body Plans Developmental Origins in Triploblasts Body Plans n Spiral cleavage n Ecdysozoan protostomes n Produces embryos whose developmental n
n Exhibit a range of cleavage pattern contrast with those of pattern
deuterostomes n Blastopore becomes the mouth n
n Cleavage is mosaic n
n Mesoderm forms from 4d cell n
n May be acoelomate, pseudocoelomate, or n
coelomate (schizocoely) n Animals with these features are called n
lophotrochozoan protostomes 9­25 patterns including spiral cleavage n Coelomate or psuedocoelomate 9­26 Copyright © The McGraw­Hill Companies, Inc. Permission required for reproduction or display. Copyright © The McGraw­Hill Companies, Inc. Permission required for reproduction or display. A Complete Gut Design and Segmentation Few diploblasts and triploblasts form Few diploblasts and triploblasts form blind blind gut n Same opening for entrance of food and n
exit of wastes n Most form a n
Most form a complete gut complete gut n Allows for one n
Allows for one­ ­way flow of food from way flow of food from mouth to anus n Tube n
Tube­ ­within within­ ­a a­ ­tube design tube design n n
9­27 9­28 Copyright © The McGraw­Hill Companies, Inc. Permission required for reproduction or display. Copyright © The McGraw­Hill Companies, Inc. Permission required for reproduction or display. A Complete Gut Design and Segmentation n Metamerism (Segmentation) n
n Serial repetition of similar body segments n
along longitudinal axis of body n Each segment is a n
Each segment is a metamere or somite metamere or somite n Permits n
Permits greater body mobility greater body mobility and and complexity complexity of structure and function n Annelids, Arthropods, Chordates n
9­29 9­30
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Copyright © The McGraw­Hill Companies, Inc. Permission required for reproduction or display. Copyright © The McGraw­Hill Companies, Inc. Permission required for reproduction or display. Components of Metazoan Bodies Components of Metazoan Bodies n Extracellular Components n
n n
n Cellular Components: Tissues n
Noncellular components of metazoan animals n Body fluids n
n Extracellular structural elements n
9­31 n Histology n
Histology is the study of types of tissues is the study of types of tissues n Four major types n
Four major types of tissues of tissues form during form during embryonic development n Epithelial Tissue n Connective Tissue n Muscular Tissue n Nervous Tissue 9­32 Copyright © The McGraw­Hill Companies, Inc. Permission required for reproduction or display. Copyright © The McGraw­Hill Companies, Inc. Permission required for reproduction or display. Components of Metazoan Bodies n Epithelial Tissue n Sheet of cells that covers an internal or external surface n Avascular n Function n
n Protection n Absorption n Secretion 9­33 9­34 Copyright © The McGraw­Hill Companies, Inc. Permission required for reproduction or display. Copyright © The McGraw­Hill Companies, Inc. Permission required for reproduction or display. Components of Metazoan Bodies
Components of Metazoan Bodies n Simple epithelia n Single layer of cells n Found in all metazoa n Stratified epithelia n 2 or more cell layers n Restricted to vertebrates n Separated from underlying tissues by a basement membrane 9­35 9­36 6
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Copyright © The McGraw­Hill Companies, Inc. Permission required for reproduction or display. Copyright © The McGraw­Hill Companies, Inc. Permission required for reproduction or display. Components of Metazoan Bodies n Connective Tissue n
n Widespread in body n
n Contains relatively few cells, many fibers, n
and a ground substance or matrix n 2 types n
2 types of connective of connective tissue proper In vertebrates n Loose connective tissue n
n Contains fibers and both fixed and wandering n
cells in a viscous fluid matrix n Dense connective tissues n
n n
9­37 Characterized by densely packed fibers and little matrix n Connective tissue also includes blood, lymph, n
cartilage, and bone 9­38 Copyright © The McGraw­Hill Companies, Inc. Permission required for reproduction or display. Copyright © The McGraw­Hill Companies, Inc. Permission required for reproduction or display. Components of Metazoan Bodies n Muscular Tissue n
n Most abundant tissue n
Most abundant tissue in most animals in most animals n Originates from n
Originates from mesoderm n Muscle cell called a n
Muscle cell called a muscle fiber muscle fiber n Specialized for contraction n
n 3 types n
n Skeletal n
n Striated, unbranched, multinuclei, and voluntary n
n Cardiac n
n Striated, branched, 1 n
Striated, branched, 1­ ­2 nuclei, involuntary 2 nuclei, involuntary n Smooth n
n No striations, unbranched, 1 nucleus, involuntary n
9­39 9­40 Copyright © The McGraw­Hill Companies, Inc. Permission required for reproduction or display. Copyright © The McGraw­Hill Companies, Inc. Permission required for reproduction or display. Components of Metazoan Bodies
Components of Metazoan Bodies n Nervous Tissue n
n Specialized to receive stimuli and n
conduct impulses from one region to another n 2 basic cell types n
n Neurons n Structural and functional unit of nervous system n Neuroglia n Insulate and support neurons. 9­41 9­42 7
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Copyright © The McGraw­Hill Companies, Inc. Permission required for reproduction or display. Copyright © The McGraw­Hill Companies, Inc. Permission required for reproduction or display. Complexity and Body Size More complex grades of metazoan organization n Permit and promote evolution of large n
body size n As body increases in size n n n
Surface ­area Surface­ area­ ­to to­ ­volume ratios have important volume ratios have important consequences for animal respiration, heat, etc. n Surface area increases as the square of body n
length n Volume increases as the cube of body length n
n n
9­43 n n
9­44 Copyright © The McGraw­Hill Companies, Inc. Permission required for reproduction or display. Copyright © The McGraw­Hill Companies, Inc. Permission required for reproduction or display. Complexity and Body Size Complexity and Body Size A large animal has less surface area A large animal has less surface area compared to its volume than does a smaller compared to its volume than does a smaller animal n n
May be inadequate for respiration and nutrition by cells located deep within its body Flattening or infolding the body increases surface area, as in flatworms n Most animals n
Most animals developed internal transports developed internal transports systems to shuttle nutrients, gases and waste products, as they became larger n n
9­45 “Cope’s Law of Phyletic Increase” n Lineages began with small individuals and n
eventually evolved toward giant forms n Large forms frequently became extinct n
n Provided opportunities for new lineages, n
which in turn evolve larger forms n Holds for many n
Holds for many nonflying vertebrate and nonflying vertebrate and invertebrate groups n n
9­46 Copyright © The McGraw­Hill Companies, Inc. Permission required for reproduction or display. Copyright © The McGraw­Hill Companies, Inc. Permission required for reproduction or display. Complexity and Body Size
Complexity and Body Size n Benefits of Being Large n
n Buffers against environmental fluctuations n
n Provides protection against predators and n
promotes offensive tactics n Cost of maintaining body temperature is n
less per gram of body weight than in small animals n Energy costs of moving a gram of body n
weight over a given distance less for larger animals 9­47 9­48 8
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Copyright © The McGraw­Hill Companies, Inc. Permission required for reproduction or display. Copyright © The McGraw­Hill Companies, Inc. Permission required for reproduction or display. Geologic Time Scale 9­49 9­50
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