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Incomplete Gut- gut with only an opening at the blastopore (a.k.a blind gut)

Complete Gut- has two openings (mouth and anus)

Diploblastic- animals with two germ layers

Triploblastic- animals with three germ layersMesoderm- between the ectoderm and the endoderm (muscular system, reproductive system,

peritoneum, calcareous plates)

-initial cells of mesoderm come from endoderm

Coelom- body cavity completely surrounded by mesoderm

-when coelom formation is complete, the body has three germ layers and two cavities(gut and coelomic cavity)

D euterostome D evelopment:

Radial Cleavage- embryonic cells are arranged in radial symmetry around the animal vegetalaxis

Regulative Development- fate of cell is not fixed early in development; in early developmenteach cell is able to produce an entire embryo if separated from other cells

-blastopore becomes the anus

-coelom formation is enterocoely

Enterocoely- both mesoderm and coelom are mad at the same time

-there are variations in deuterostome cleavage

*Bilateral Cleavage- (ex. Ascidian chordates) anteroposterior axis is established prior tofertilization; first cleavage furrow passes through the animal-vegetal axis

Rotation Cleavage- (isolecithcal) cells at the second cell division appeqar to have turned relativeto each other (90 degrees)

Trophoblast- form embryonic portion of the placenta when the embryo implants in the uterinewall

Inner cell mass- cells that give rise to the embryo proper form here (in mice)

Discoidal Cleavage- (telolecithal) due to great mass of yolk, cleavage is confined to a small discof cytoplasm lying atop a mound of yolk (in chickens)

-coelomic vesicles: (deuterostome) pinch off from archenteron to form left and rightcoelomic compartments

*-primitive streak: the anteroposterior axis of the embryo and the center of early growth


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-Blastoderm consists of two layers: epiblast and hypoblast with blastocoels betweenthem

-Epiblast and hypoblast end up forming endoderm and mesoderm

Protostome D evelopment:

Spiral Cleavage- blastomeres cleave at 45-degree angles; cells lie between cells of the underlyinglayer

Mosaic Development- embryonic development is characterized by each part of the embryo

Morphogenetic Determinants- determined by distribution of certain proteins and mRNAs (this iswhy Protostome is mosaic)

-blastopore becomes the mouth

-coelom formation is schizocoely

Schizocoey- coelom formed by the splitting of embryonic mesoderm

-some protostomes do not develop a coelom

Acoelomate- animals without a coelom

Pseudocoelom- a body cavity formed from a persistent blastocoels and linked with mesoderm ononly one side

Lophotrochozoan Protostomes- (segmented worms & mollusks) have lophophore or trochophorelarva

Ecdysozoan Protostomes- (arthropods) members shed their cuticle as they grow

*Superficial Cleavage- centrally located mass of yolk restricts cleavage to the cytoplasmic rim of the egg


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Chapter 9

Grades of Organization

1. Protoplasmic Grade (unicellular)

2. Cellular Grade3. Cell-Tissue Grade

4. Tissue-Organ Grade

5. Organ System Grade

Metazoa- multicellular animals

Eumetazoan- multicellular animals with distinct germ layers that form true tissues

Parenchyma- chief functional cells of an organ

Stroma- supportive tissue

Organ Systems: skeletal, muscular, urinary, reproductive, nervous, digestive, integumentary,respiratory, circulatory, excretory, endocrine and immune

-Animal body plans differ in the grade of organization, in body symmetry, in the number of embryonic germ layers and in the number of body cavities

*Spherical Symmetry- any plane passing through the center divides a body intoequivalent/mirrored image; chiefly among unicellular organisms

*Radial Symmetry- can be cut in more than one way to be symmetrical*Biradial Symmetry-

Bilateral Symmetry- animals that can be divided along a sagittal plane into two mirrored portions

Cepalization- sensory organs and specialized appendages become localized in the head end of animals

Anterior- head area Posterior- tail end

Dorsal- back side Ventral- front/belly side

Lateral- the sides Distal- parts farther from the middle of the body

Proximal- parts closer to the body

Frontal Plane- divides body into dorsal and ventral

Sagittal Plane- divide animal into right and left halves

Transverse Plane- separates anterior from posterior at middle of body


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Pectoral- chest region Pelvia- hip region

Acoelomate- mesodermal cells completely fill the blastocoels, leaving the gut (archenteron) asthe only body cavity

*parenchyma- a spongy mass of space-filling cells between the ectodermal epidermis andthe endodermal digestive tract

Pseudocoelomate- mesodermal cells line the outer edge of the blastocoels, leaving two bodycavities

Pseudocoelom- a false coelm, where the blastocoels was

Peritoneum- thin cellular membrane derived from medoderm lining it

Mesenteries- suspended organs in the coelom

-Pseudocoelom lacks a peritoneum

Segmentation (metamerism)- serial repetition of similar body segments along longitudinal axisof the body

Metamere/Somite- the segments that make up the segmentation

-segmentation permits greater body mobility and complexity of structure and function

-Metazoan animals contain two noncellular components

1. Body Fluids (separated into two fluid components)

-Intracellular Space- within the bodys cells

-Extracellular Space- outside the cells

-blood plasma- fluid portion of body

-interstitial fluid-(tissue fluid) occupies the space surrounding cells

2. Extracellular Structural Elements (supportive material of the organism) ex. Looseconnective tissue, cartilage, bone and cuticle

Tissue- group of similar cells specialized for performance of common function

Histology- study of tissues

Epithelial Tissue

-sheet of cells that covers an external or internal surface

-a large variety of transport molecules are located on epithelial cell membranes


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Connective Tissue

-diverse group of tissues that serve carious binding and supportive functions

-specialized connective tissue: blood, lymph, adipose, cartilage and bone

Ground Substance- fibers are suspendedLoose Connective Tissue- composed of fibers and both fixed and wandering cellssuspended in a viscous fluid ground substance

Dense Connective Tissue- composed largely of densely packed fibers and little groundsubstance (ex. Tendons and ligaments)

Collagen- protein of great tensile strength

Muscular Tissue

-the most abundant tissue in the body o most animals

-originates from mesoderm

-its unit is the muscle fiber

-Sarcoplasm- unspecialized cytoplasm of muscles

-Myofibrils- contractile elements within the fiber

Nervous Tissue

-specialized for reception of stimuli and conduction of impulses from one region to

another -Neurons- basic functional unit of nervous system

-Neuroglia- variety of nonnervous cells that insulate neuron membranes and servevarious supportive functions

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