1. 1 Chapter 3 Animal Architecture Biological organization is essentially uniform deriving from a common ancestry of animals & from their basic cellular construction.

2. 2 Chapter 3 Homework  Read pages 54-56 Animal Body Plans  Look at & understand Table 3.1 Levels of Organization  Read pages 57-61 Body plans & body cavities  Understand Fig. 3.7  Do Questions 1, 10, 12, 13, 16 pages 70-71  Due 2/16/10

3. 3 5 Levels of Organization in Organisms  1. Protoplasmic level Unicellular organisms Remarkable organization & division of labor of subcellular structures & organelles  Protozoa displays this type of organization

4. 4  2. Cellular level Multicellular organisms  Aggregation of cells that are functionally differentiated  Division of labor in cells ie, some reproductive cells, some digestive cells, some sensory cells  Individual cells usually incapable of independent existence  Metazoans display this type of organization; some place sponges (Phylum Porifera) here

5. 5 Sponges

6. 6  3. Cell-Tissue level  Cells aggregated into definite layers or patterns displaying a distinct function – a tissue  Cells of this organism type are generally not too organized  Cnidarians & Ctenophera found here; some place sponges here too For Cnidarians the nerve net is a good example of a tissue

7. 7 Cnidaria

8. 8

9. 9 Ctenophera

10. 10 Benthic Slug - Ctenopheran

11. 11  4. Tissue-Organ level  Tissues aggregate into a functioning unit – an organ Usually have several tissue types composing it; function is usually specialized Parenchyma – term for the tissue type that carries out the organs prime function (ie, muscle tissue in heart) Stroma – term for tissue type in supportive functional role  Platyhelminthes found here Have very well defined digestive, sensory & reproductive organs

12. 12 Platyhelminthes

13. 13 Platyhelminthes

14. 14 Are these the same organism? Why or Why Not? Look closely…….

15. 15  5. Organ-System level  A system is associated with basic body functions like circulation, respiration, digestion…  Nemertean worms are simplest animal displaying this type of organization, whereas, most animal phyla display this organization type

16. 16 Nemertean Worms Bootlace or Ribbon Worms

17. 17 Nemertean Worms  Carnivorous  Evert proboscis

18. 18 Symmetry Balanced Proportions  A. Spherical symmetry Any plane passing thru the center divides body into equivalent (mirrored) halves Found in protozoans, rare in metazoans  B. Radial symmetry If 2+ planes are passed thu the longitudinal axis, similar halves are made Found in hydras, sea urchins, jellyfish, some sponges  C. Biradial symmetry (variant form of B) Only 1 or 2 planes passed thru longitudinal axis form mirrored halves Found in Ctenophera (comb jellies)

19. 19

20. 20 Biradial Symmetry Example: Comb Jelly Courtesy of Dr. Richard Fox, Lander University

21. 21  D. Bilateral symmetry Any plane passing thru sagittal plane divides body into mirrored portions; right & left Cephalization strong in bilaterally symmetrical bodies  Concentration of nervous tissue; sense organs Bilateral organisms better adapted for forward movement

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23. 23 Terms used in bilaterally symmetrical bodies:  Anterior – head end  Posterior – tail (opposite) end  Dorsal – back side  Ventral – belly side  Lateral – sides  Distal – parts farthest from middle  Proximal – part nearer  Frontal plane – divides body into dorsal/ventral  Sagittal plane – divides body into right/left  Transverse plane – divides body into cross sections

24. 24 Courtesy of Dr. Richard Fox, Lander University

25. 25 Development of Animal Body Plans  Fertilized egg forms zygote, which is a single large cell until it begins cleavage Cleavage forms blastomeres  2 cleavage types Radial – echinoderms, chordates, hemichordates Spiral – molluscs, annelids, protostomes  Exception: sponges & cindarians lack distinct cleavage patterns

26. 26 Spiral Cleavage  Cleavage planes are oblique to polar axis producing a quartet of cells laying not atop each other, but between cells.  Cells tend to pack tightly like “soap bubbles”  Known as mosaic cleavage because organ-forming cells already “programmed”, so if cells become separated during development, they do not have ability to form complete individual

27. 27 Radial Cleavage  Cleavage planes symmetrical to polar axis producing layers of cells on top of each other  Blastomeres capable of, if separated, adjusting its development into a complete individual Known as regulative cleavage

28. 28 Further embryo development  Cleavage proceeds until zygote forms blastula (ball of cells) surrounding blastocoel (fluid-filled cavity)  Blastula invaginates into a 2-layered gastrula (except sponges); outer germ layer is ectoderm surrounding blastocoel and inner germ layer is endoderm surrounding the newly formed gastrocoel  The invagination continues, forming a tube, the “gut”

29. 29 Body Cavities (pg 58-9 Text)  Pseudocoelom Mesoderm (middle germ layer) occurs next to ectoderm Have a “false” body cavity surrounding gut (tube within a tube arrangement) Lacks peritoneum (mesoderm deriver membrane surrounding body cavity  Acoelom Mesoderm completely fills blastocoel cavity No body cavity surrounding gut  Coelom Mesoderm fills blastocoel, then a 2 nd cavity forms inside mesoderm This arrangement provides space for viscera, permits greater size/complexity due to more cells exposed to surface area exchange

30. 30 Cavity Comparison

31. 31 Coelomates  Divided into 2 groups Protostomia (“first mouth”)  Mouth forms from first embryological opening, the blastopore Deuterostomia (“second mouth”)  Anus forms from blastopore, mouth forms secondarily  Form in 1 of 2 ways: Schizocoely (most protostomes) Enterocoely (most deuterostomes) Once completed, coelom is indistinguishable See Fig 3.9, pg 64 

32. 32 Segmented Body Plans (Metamerism)  Serial repetition of body segments along longitudinal axis of body Segments- metameres, somites  True metamerism seen in only 3 phyla Annelida, Arthropoda, Chordata See next 3 slides for examples

33. 33 Phylum Annelida Bearded Fireworm Bristleworm

34. 34 Phylum Arthropoda

35. 35 Phylum Chordata  Amphioxus Notice segmentation of many body structures

36. 36 Metazoan Body Plans  Composed of tissues derived from 3 germ layers & extracellular components  Histology – study of tissues  4 Tissue types: Epithileial Connective (inclu vascular) Muscular Nervous

37. 37 Epithelial Tissue  Sheet of cells covering external & internal surface, lining ducts, organs, passageways  Cells often modified for secretion of mucous, hormones, enzymes, etc  Supported by a base membrane  Blood supply never enters epithelia

38. 38 Connective Tissue  Serve binding & support functions  Composed of few cells, extracellular fibers, & ground substance (rigid, gel-like) There is loose and dense (tendons, ligaments) connective tissue Collagen – protein in connective tissue  Other types of connective tissue Blood Lymph Cartilage Bone Tissue fluid

39. 39 Muscular Tissue  Originates in mesoderm  Types: Striated: transversely striped  Skeletal & cardiac Visceral: lacking banding  Sarcoplasm – muscle cytoplasm  Myofibrils – contractile elements in muscle fibers

40. 40 Nervous Tissue  Specialized for stimulus reception & transmission of impulses  2 types of cells Neurons – basic functional unit Neuroglia – insulate neurons

41. 41 Complexity of Body Size  Surface area to volume must be considered when thinking about body size As volume increases the ratio of surface area to volume decreases  Why is this a problem? Animals rely on environment to provide its needs – O 2, food, gas exchange, waste emission  If surface area to volume ratio is even, organism is able to meet needs thru simple diffusion

42. 42 So what, you say…  Bigger organisms are better able to exploit environment and survive, but how does the bigger body supply its needs?  2 ways: Flatten body (like platyhelminthes) so no internal structure is far from surface Or, develop some sort of transport mechanism to move stuff in/out  Most animals have evolved using the 2 nd option – greater internal organization supporting transport of necessary materials into and out of body  Generally, the unit cost to the bigger body is pretty efficient