ch9

Chapter 9Architectural Pattern of an

Animal

New Designs for Living

Levels of Organization in Organismal Complexity

• Zoologists recognize 34 major phyla (multicellular animals)

• 600M years ago, nearly 100 phyla evolved representing nearly all major modern body plans

• Major body plans - result of extensive selection- determinant of future adaptational variants

• Animals share structural complexities that reflect common ancestry

Hierarchical Organization of Animal Complexity

Grades of Organization

• Unicellular protozoan groups are the simplest animal-like organisms.

a.Within the cell, they perform all basic functions

b.Diversity is achieved by varying architectural patterns of subcellular structures, organelles and the whole cell

Metazoa - multicellular• Cells become specialized parts of a

whole organism; these cells cannot live alone as do protozoan cells

• Cellular grade of organization - Simplest metazoans- not strongly associated to perform a collective function

• tissue grade organization - More complex metazoans have cells working closely together as a unit.**parenchyma - chief functional cells of an organ **stroma - supportive tissues

• Many tissues work together in an organ; most metazoans operate at the organ system level

Animal Symmetry• Spherical symmetry - when any plane

divides the body into mirrored halves, as in cutting a globe in half

• Radial symmetry - when any plane passing through the longitudinal axis divides the body into mirrored halves, as in cutting a pie

• E.g. Cnidaria and Ctenophora are the Radiata

Biradial symmetry - in an animal that is radial, except for some paired feature that allows only two mirrored halves (comb jellies)

bilateral symmetry - organism can be cut in a sagittal plane into two mirror halves; this usually provides for a head (cephalization) in bilateral animals classified in the Bilateria

Cephalization• Differentiation of the head, or cephalization, is

mainly found in bilaterally symmetrical animals

Body Cavities and Germ Layersbody cavity - an internal space• Most obvious is a gut cavity• Most animals have a second cavity outside the

gut• fluid-filled cavity - cushion and protect the gut• Coelom provides more space for organs and

surface area for exchange.• Worms rely on the coelom for a

hydrostatic skeleton to aid in burrowing

• Sponges have no body cavity• Like all metazoans, sponges develop from a

zygote to a blastula stage• In sponges, after the formation of a blastula, the

cells reorganize to form the adult animal

Methods of Mesoderm formation• mesoderm forms as endodermal

cells migrate into the blastocoelthree body plans1. acoelomate plan - mesodermal

cells completely fill the blastocoel

2. pseudocoelomate plan - mesodermal cells line the outer edge of the blastocoel, leaving a persistent blastocoel and a gut cavity.

3. eucoelomate - blastocoel is completely lined with mesoderm forming a true coelom

2 different eucoelomate plans

a. schizocoelous - mesodermal cells fill the blastocoel; then a space opens inside the mesodermal band forming a coelom

b. enterocoelous - cells from the central portion of the gut lining begin to grow outward as pouches

• The expanding pouch walls form a mesodermal ring and enclose a space which becomes a coelomic cavity.

Body Plans Among Major Animal Taxa

Eumetazoans show great variety in symmetry, number of body layers, and gut structure

Metamerism (Segmentation)

• Metamerism - serial repetition of similar body segments

• Each segment is a metamere or somite.

• True metamerism is found in Annelida, Arthropoda and Chordata

Components of Metazoan Bodies

A. Extracellular Components

Body fluids and extracellular structural elements - noncellular components of metazoans (intra & extra)

• Blood plasma and interstitial fluid

- part of the extracellular fluids in open and closed circulatory systems.

Cellular Components: Tissues

Epithelial Tissue

a.Epithelium - sheet of cells that covers an internal or external surface

• provides outside protection and internal linings• Simple epithelia are found in all metazoa.• Stratified epithelia are restricted to vertebrates.• All epithelia have an underlying basement

membrane.• Blood vessels never penetrate epithelial tissues.

Simple squamous :Cheek cells

Simple Columnar :Intestine/stomach

Transitional : Urinary bladder

tracheaUpper layer of skin

Not strictly squamous,Cuboidal or epithelial

Connective Tissue• Made up of few cells, many extracellular fibers and a

ground substance or matrix.Two types of connective tissue proper (vertebrates) 1) Loose connective tissue - fibers and both fixed and

wandering cells in a syrupy matrix2) Dense connective tissues (e.g., ligaments and tendons)

are characterized by densely packed fibers.• Much fibrous tissue is made of protein collagen, the most

abundant protein in the animal kingdom.

Connective tissue fibers• Collagen – thick,

unbranched, spread, wavy

• Elastic – thin, less wavy, branched

• Reticular – fine & delicate

Classification of connective tissues

I. Connective tissue proper – for binding purposes

a. Loose/areolar – large amount of tissue fluid, many cells, few

fibers b. dense/tendon – more fibers, decrease in fluid & cells

II. Specialized connective tissue – has other specific functions aside from binding

a. Adipose – adipocytes

- store fats & nutrients, provide insulation, act as cushion

- fusiform nucleus

b. Cartilage – chondrocytes- housed inside a matrix called Lacuna

3 types of cartilage accdg to matrix:1. Hyaline – e.g cartilage of trachea

- clear homogenous matrix

2. Elastic cartilage – in epiglottis & external ear

- similar to hyaline except for the elastic fibers present

3. Fibrocartilage – consist of network of collagenous fibers

c. Bone – osteocytes

- support, protection, movement, formation of blood cells, reservoir of calcium

d. Blood

– transport medium of the body

Plasma – fluid medium where all cell types are found

1. Erythrocytes – frog/human

Leucocytes

2. Leucocytes – granulated & agranulated

Granular wbc

• Granulated cytoplasm & polymorphous/multi-lobulated nucleus

• Connected by chromatin strands

1. Eosinophils – 2 lobes; pink to red granules

2. Basophils – S-shaped; blue

3. Neutrophils – 3-5 lobes ; purple

Agranular wbc• Monocyte – kidney-shaped/oval nucleus

• Lymphocyte – large nucleus

Thrombocytes

• Platelets – minute cytoplasmic fragments

Agranulated Granulated

platelets

Muscular Tissue

• most abundant tissue in most animals.• originates from mesoderm.• muscle fiber - cells specialized for contraction.• Striated muscles include skeletal and cardiac

muscles.• Smooth muscles lack the alternating bands seen

in striated muscle.• Myofibrils are contractile elements and the

unspecialized cytoplasm is sarcoplasm

Muscle tissue

• Contractility

• Muscle fibers

• 3 types

Nervous Tissue• receives and conducts impulses

• Nervous tissue cell types are neurons and neuroglia that support the neurons.

Complexity and Body Size

• More complex grades of metazoan organization permit and promote evolution of large body size.

• Surface-area-to-volume ratios have important consequences for animal respiration, heat, etc.

• Most animals had to develop internal transports systems to shuttle nutrients, gases and waste products, as they became larger

• “Cope’s Law of Phyletic Increase” - lineages began with small individuals and eventually evolved toward giant forms; it holds for nonflying vertebrates and many invertebrates.