Animal Evolution

•Precambrium Sea•Multicellular•Competition

Characteristics of animals•Animals are multicellular heterotrophic eukaryotes

•Ingestion to make inorganic chemicals

•Animal cells lack cell walls and are held together by proteins (collagen)

•Nervous Tissue and Muscle Tissue

•Reproduce sexually with the diploid stage being dominant

Early Embryonic Development

Cleavage: mitotic divisionMultiple cells combine

Blastula: hollow ball of cellsHollow portion called Blastocoel

Embyronic LayersForm.Endoderm and Ectoderm

Traditional “Body Plans”•Major characteristics, embryonic development•Major branches called Grade

1. Parazoa-Eumetazoa: Formation of Tissues

2. Radiata-Bilateria:

3. Acoelomate-Pseudocoelomate-Coelomate

4. Protostome-Deuterostome:

Figure 32.5 Body symmetry

Radiata-Bilateria Dichotomy•Bilateralism forms: Dorsal, Ventral, Anterior, Posterior

•Cephalization: adaptation for movement.•Germ Layers: various layers of cells in development.

•Ectoderm: gives rise to outer covering, CNS•Endoderm: innermost layer, digestive tube•Mesoderm: b/w other two layers, muscle and other organs

•Diploblastic: two germ layers (radiata)•Triploblastic: Three germ layers (bilateria)

Protostome-Deuterostome Dichotomy

Protostome: mollusks, annelida, arthropodaDeuterostomes: Echinodermata, Chordata

•Cleavage: division of cells, •Spiral Cleavage: Protostomes, Early developmental fate, •Radial Cleavage: Deuterostomes, indeterminate cleavage

•Coelom Formation:

Blastophore Fate:Protostome: blastophore forms mouthDeuterostome: blastophore forms anus