What is an animal?

Animals are multicellular, heterotrophic eukaryotes with tissues that develop from embryonic layers.

How do animals differ

from plants?

Animals lack cell walls and havehave collagen as their mostabundant protein.

Animals have nerve and muscle cells.

Animals have three distinct cell junc-tions: tight junctions, desmosomes, and gap junctions.

Early Embryonic Development

A Traditional View of Animal Diversity Based on Body-Plan Grades

Body Symmetry in Animals

Body Plans of the Bilateria

Protostomesvs. Deuterostomes

Animal Phylogeny Based on Sequencing of SSU-rRNA

Figure 47.6x Sea urchin development, from single cell to larva

Cleavage in an echinoderm (sea urchin) embryo

Cleavage in a frog embryo

Cross section of a frog blastula

Gastrulation in a frog embryo