KINGDOM ANIMALIACharacteristics of Animals January 16th, 2007
Characteristics of Life1. Living things are organized.2. Living things are made up of cells.3. Living things metabolize.4. Living things maintain an internal environment.5. Living things grow.6. Living things respond.7. Living things reproduce.8. Living things evolve.
Seven Levels Kingdomof Taxonomic PhylumClassification Class Order Family Genus Species
Kingdom Animalia All animals are multicellular,mitochondrial heterotrophs—theyhave multiple cells withmitochondria and they rely on otherorganisms for their nourishment. Most animals ingest their food andthen digest it in some kind ofinternal cavity.
Animal Species Somewhere around 9 or 10million species of animalsinhabit the earth. About 800,000 species havebeen identified.
Animal Phyla Biologists recognize about 36separate phyla within theKingdom Animalia. Animal Phyla Web Page
Animal Movement Most animals are capable ofcomplex and relatively rapidmovement compared to plantsand other organisms.
Animal Reproduction Most animals reproduce sexually,by means of differentiated haploidcells (eggs and sperm). Most animals are diploid, meaningthat the cells of adults contain twocopies of the genetic material.
Animal Sizes Animals range in size from nomore than a few cells (like themesozoans) to organismsweighing many tons (like theblue whale). a mesozoan blue whale
Animal Habitats Most animals inhabit the seas,with fewer in fresh water andeven fewer on land.
Animal Cells Animal cells, like all eukaryoticcells, have internal structurescalled organelles that servespecific functions for the cell. Animal cells lack the rigid cellwalls that characterize plantcells.
Animal Bodies The bodies of most animals(all except sponges) are madeup of cells organized intotissues. Each tissue is specialized toperform specific functions. In most animals, tissues areorganized into even morespecialized organs.
Animal Symmetry The most primitive animals areasymmetrical. Cnidarians and echinodermsare radially symmetrical. Most animals are bilaterallysymmetrical.
Radial Symmetry …applies to forms that can bedivided into similar halves bymore than two planes passingthrough it. Animals with radial symmetryare usually sessile, free-floating,or weakly swimming.
Bilateral Symmetry Animals with bilateralsymmetery are most well-suitedfor directional movement.
Cephalization Bilateral Symmetry usually hasled to cephalization—theprocess by which sensoryorgans and appendages becamelocalized in the head end ofanimals.
Evolutionary TrendsIf we analyze the basic body plansof animals, we find that theyillustrate evolutionary trends.Four major “advances” (in order): 1. Multicellular body plan 2. Bilaterally symmetrical body plan 3. “Tube-within-a-tube” body plan 4. Coelomate body plan
3 Major Bilateral Body Plans Acoelomates Pseudocoelomates Coelomates Each plan consists of 3 cell layers: endoderm, mesoderm, ectoderm
Acoelomates These animalshave no othercavity than thegut. They are oftencalled the “solidworms.”
Pseudocoelomates These animals have abody cavity (thepseudocoelom) whichis not completelylined with mesoderm. The “tube within atube” body plan. This category is alsocomposed of mostlyworms.
Coelomates These animals havea “true coelom”lined withmesodermalperitoneum. Most animals arecoelomate.