Ch30 (2)

Chapter 30

ANIMALS

Six Kingdoms are usually recognized: Prokaryota, Archaea, Protoctista, Fungi, Plantae and  Animalia !he "ord animal comes animal  comes #rom the $atin %anima%, "hich means soul or &reath !he #ollo"ing notes ha'e &een taken #rom the &ook &y (argulis and Sch"artz, %Fi'e Kingdoms%, 3rd )dition, *++ •

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 Animals are heterotrophic, heterotrophic, diploid, diploid, multicellular multicellular organisms organisms that usually usually -except. -except. sponges. sponges. de'elop #rom a &lastula !he &lastula, a multicellular em&ryo that de'elops #rom the diploid zygote produced &y #ertilization o# a large diploid egg &y a smaller haploid sperm, is uni/ue to animals !he gametes o# animals, eggs and sperms, di##er in size and #orm and are called anisogametes anisogametes 

ther characteristics that can &e added to those a&o'e are: eukaryotes, "ith cells specialized and organized into tissues, organs, etc1 they inha&it the sea, #resh "ater and land1 most are capa&le o# locomotion at some stage o# their li'es1 most can respond adapti'ely to external stimuli and ha'e "ell de'eloped sense organs and ner'ous system1 most reproduce sexually, "ith large non2motile eggs and small #lagellated sperms !he diploid zygote produced &y #ertilization di'ides &y mitotic di'isions, resulting in a &all o# cells that usually hollo"s out to &ecome a &lastula !he kingdom Animalia is di'ided into a&out 3 phyla -sing phylum. Phyla are distinguished #rom each other &y the &ody plan, the ma4or #eatures o# its structural and #unctional design

THE ARCHITECTURE OF ANIMALS. Four #eatures are commonly used to distinguish the &ody plan o# animals: * !he !he num& num&er er o# tissue layers #ound layers  #ound in the em&ryo: diplo&last or triplo&last 5 !he !he typ type o# body symmetry: symmetry: radial or &ilateral 3 Presenc Presence e or a&se a&sence nce o# a &ody #luid2#il #luid2#illed led body a!ity: a!ity: acoelomates, pseudocoelomates, or coelomates 6 !he !he pat patte tern rn o# early embryoni de!elo"ment: de!elo"ment : protostomes or deuterostomes Embryoni tissues.  A tissue is an an organized organized and #unctional #unctionally ly integrated integrated group o# o# cells #i"loblasts ha'e #i"loblasts ha'e t"o em&ryonic layers o# tissue, the endoderm and the ectoderm

7n tri"loblasts there tri"loblasts there are three layers present, the endoderm, endoderm , the mesoderm and mesoderm  and the etoderm etoderm 

$ody symmetry.  A &ody is symmetrical symmetrical i# it can can &e di'ided di'ided in a "ay that results in similar similar sides Asymmetry Asymmetry  !hey cannot &e section in a "ay that produces similar parts Some sponges are asymmetrical Radial symmetry has symmetry  has t"o planes o# symmetry1 the &ody is shaped like a cylinder or a disk "ith parts radiating #rom a central point $ilateral symmetry has symmetry  has only one plane o# symmetry di'iding the &ody into t"o sides, le#t and right1 the &ody is usually long and narro" "ith a head and tail !ypes o# sectioning a specimen: • • •

Sagittal setion di'ides setion di'ides the &ody into rig%t and le&t "arts "arts  Cross or trans!erse setion di'ides setion  di'ides the &ody into anterior and "osterior "arts "arts  Frontal setion di'ides setion di'ides the &ody into dorsal and !entral "arts "arts 

 All triplo&lastic triplo&lastic animals animals ha'e &ilateral &ilateral symmetry, symmetry, except the adult #orm o# the echinode echinoderms, rms, eg star#ish 8ilateral symmetry is the most common !he reason #or this is •

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9nidirectional mo'ement o# the animal #or &etter sensing the en'ironment -senses on the head., and easier to #ind #ood ith the mesoderm, ner'ous and muscular systems de'eloped allo"ing directional mo'ement possi&le

$ody a!ity  Animals may &e • • •

Aoelomate: Aoelomate : lack coelom or &ody ca'ity, eg cnidarians, ctenophores, #lat"orms 'seudooelomate(  coelom is partially lined "ith mesoderm, eg round"orms, roti#ers Coelomate: Coelomate : coelom is completely lined "ith mesoderm

;iplo&last lack a &ody ca'ity !riplo&lasts ha'e either a #alse coelom or a true coelom  Ad'antages  Ad'antages o# the the coelom: • • •

Pro'ides space #or many organs to #unction "ith #reedom, eg heart, gonads  Allo"s the digesti'e ca'ity ca'ity to mo'e mo'e independentl independently y o# &ody mo'ements