Lab #7: Introduction to the Kingdom Animalia Objectives: 1 ...

3. Out of all the organisms you examined, is there a particular pattern between the
organisms that have bilateral symmetry Radial symmetry Make sure to consider
morphology.
Task 4: Developmental patterns in bilateral animals: Protostomes and Deuterostomes
Bilateral animals follow two major patterns of embryonic development. Based on these patterns
they are classified as either deuterostomes or protostomes. In deuterostomes, the blastopore (first
embryological opening) becomes the anus, while in protostomes the blastopore becomes the
mouth. Also, cleavage, the initial process of cell development after a zygote is formed is
different in the two lineages: In protostomes, cleavage is spiral, while it is radial in
deuterostomes.
The separation of the metazoans (multicellular animals) into two separate lineages, suggests an
evolutionary divergence of the bilateral body plan. This suggests that deuterostomes and
protostomes are separate, monophyletic lineages. For further information, please look at table
40.1 (pg. 441) in your lab manual.
Examine the animals noted under the “Example species” below and answer the questions below
the table.