intro to animaliachapter 32

organization• Levels of organization

• cells -- tissues -- organs -- organ systems

• Tissue organization• eumetazoa

• sponges?

• constraints on form • surface area-to-volume ratio

5

11

6 150 750

125 1251

6 61.2

Total surface area[Sum of the surface areas

(height × width) of all boxessides × number of boxes]

Total volume[height × width × length ×

number of boxes]

Surface-to-volume(S-to-V) ratio

[surface area ÷ volume]

Surface area increases whiletotal volume remains constant

• animal characteristics• multicellular heterotrophs

• origins?• syncytial ciliate hypothesis, colonial flagellate

hypothesis• polyphyletic origin?• molecular evidence?

OTHEREUKARYOTES

Choanoflagellates

Sponges

Other animals

Anim

als

Individualchoanoflagellate

Collar cell(choanocyte)

• comparative morphology (body plans) • origin of tissues• body cavity• nervous systems /

symmetry• metamerism• ontogeny / embryonic

development• body cavity -- coeloms

• acoelomate -- • pseudocoelomate • eucoelomate --

CoelomBody covering

(from ectoderm)

Digestive tract(from endoderm)

Tissue layerlining coelom

and suspendinginternal organs

(from mesoderm)

Coelomate

AcoelomateBody covering

(from ectoderm)

Wall of digestive cavity(from endoderm)

Tissue-filled region

(from mesoderm)

Pseudocoelom

Body covering(from ectoderm)

Muscle layer(from

mesoderm)

Digestive tract(from endoderm)

Pseudocoelomate

• symmetry • radial symmetry --

• biradial symmetry?• bilateral symmetry --

RADIAL SYMMETRY

BILATERAL SYMMETRYbiradial symmetry

segmentation• metamerism

• probably evolved 3 times• panarthropoda• chordata• annelida

• advantages:• efficient locomotion• tagmatization• redundancy

traditional classification• Tissue Layer and Body Cavity Evolution/Development

• Radiata—• Diploblastic, Acoelomate

• Bilateria—all other phyla• Triploblastic• Acoelomate—Platyhelminthes…• Pseudocoelomate—Rotifera, Nematoda…• Eucoelomate—all other animal phyla

• protostomes (monophyletic group?)• spiral cleavage• schizocoely• protostomous• determinate cleavage

• deuterostomes (probably a monophyletic group)• radial cleavage• enterocoely• deuterostomous• indeterminate cleavage

spiral

radial

• Traditional classification:• Protostomes—acoelomate, pseudocoelomate, eucoelomate• Deuterostomes—all eucoelomate

• Molecular studies support:• Protostomes -- monophyletic group?

• Lophotrochozoa (platy, nemert, rotif, annel, others)• Ecdysozoa (nemat, arthro, pentastomida, others)

• Deuterostomes—Chordates, Hemichordates, Echinoderms

ANIM

ALIA

segmentation

segmentation

segmentation

radial symmetry

protostomous

coelom?, CNS?, cephalization

bilateral symmetry

multicellularity

BILA

TERI

APORIFERA

CNIDARIA

CTENOPHORA

ACOELA

ROTIFERA

PLATYHELMINTHES

ANNELIDA

MOLLUSCA

NEMATA

ARTHROPODA

ECHINODERMATA

CHORDATA

CHOANOFLAGELLATES

DEUTEROSTOMIA

ECDYSOZOA

LOPHOTROCHOZOA

?

porifera• Phylum Porifera—

• Sponges; porus-pore, fera-bearing

• Sessile, aquatic• Simple cellular level of

organization - incipient tissues

porifera• sponges

• Pinacocytes• Mesohyl (Spongin, Spicules)

• Archaeocytes—ameboid cells• Choanocytes— “collar” cells

choanoderm

mesohyl

pinacoderm

anatomy• Body form—

• Asconoid• Syconoid• Leuconoid

• reproduction• asexual• sexual

ASCONOID

SICONOID

LEUCONOID

cnidarians• Phylum Cnidaria—knide – nettle,

aria – pl. of “like”• Cnidocytes - nematocyst• Radial symmetry• Tissues - simple organs• Diploblastic• classes:

• Hydrozoa• Anthozoa• Cubozoa• Scyphozoa

feeding reproduction• Asexual or sexual

• Polyp • budding• Species with reduced or

absent medusae have sexual polyps

• Medusa • typically dioecious

(gonochoristic)

adult medusa

sperm

egg

planula

strobila

ephyra

scyphistoma

youngstrobila

ctenophora• Phylum Ctenophora—“comb-bearing”

• Bi-radial symmetry (paired tentacles, double internal canals), • diploblastic• anatomy

• Collenchyme• Comb plates• Tentacles• Colloblasts

• Sexual reproduction (monoecious)

acoela• phylum acoelomorpha

• marine or brackish• usually found in sediments

• Digestion• some with gastrovascular cavity

• Reproduction • Radial nerve system

proboscis sheath

statocyst

testes

gut

mouth

ovary

gonopore