General Body Plan of Animals

General Body Plan of Animals

Throughout the evolution of animals, their body plans have undergone many changes:Evolution of Tissues-simplest animals like Parazoans (sponges) exist as simply aggregates of cells with minimal intercellular coordination.-eumetazoa (all higher animals), have distinct tissues with highly specialized cells.

General Body Plan of AnimalsEvolution of Bilateral Symmetry

-sponges lack symmetry-RADIAL symmetry- exhibited by marine animals: Cnidarians (jellyfishes, sea anemones and corals) and Ctenophorans (combjellies)—PHYLUM RADIATA

General Body Plan of Animals-BILATERAL symmetry- (PHYLUM BILATERIA) right and left mirror images; concept of dorsal/ventral, anterior end/ posterior end

General Body Plan of AnimalsBilateral symmetry allowed animals to:

-move more efficiently-have different organs

located in different parts of the body

-produce 3 germ layers: ectoderm-outer coverings, mesoderm-skeleton and muscles, and endoderm-digestive organs

-CEPHALIZATION

General Body Plan of AnimalsEvolution of Body Cavity-evolved for supporting organs, and distributing materials- 3 kinds of body plans: Acoelomates-no body cavity-flatworms: tapeworms, flukes and planarians

General Body Plan of AnimalsPseudocoelomates-with a body cavity- pseudocoel-between mesoderm and endoderm-nematodes: Ascaris

General Body Plan of Animals

Evolution of Segmentation-subdivision of the body into segments-advantages: (annelids) damage in one segment is not fatal (duplication of segment functions) and in locomotion, each segment can move independently.

General Body Plan of Animals

SEGMENTATIONMETAMERISM: each segment is similar to the other (somites/metameres).TAGMATIZATION: segments fused into functional groups (tagmata)

clitellum