1. Blastopore Fate:
- Protostomes: In protostomes, the first opening formed during embryonic development, called the blastopore, becomes the mouth of the adult animal.
- Deuterostomes: In deuterostomes, the blastopore develops into the anus of the adult animal, while a second opening forms and becomes the mouth.
2. Cleavage Pattern:
- Protostomes: Protostomes exhibit a spiral cleavage pattern during embryonic development. Spiral cleavage refers to the way cells divide, creating a spiral arrangement of blastomeres.
- Deuterostomes: Deuterostomes exhibit radial cleavage during embryonic development. Radial cleavage creates a symmetrical arrangement of blastomeres.
3. Fate of the Mesoderm:
- Protostomes: In protostomes, the mesoderm, which gives rise to various internal organs and tissues, forms from the cells located between the ectoderm and endoderm. This process is known as schizocoely.
- Deuterostomes: In deuterostomes, the mesoderm originates from pouches that emerge from the archenteron (primitive gut). This process is known as enterocoely.
4. Coelom Formation:
- Protostomes: Protostomes form their coelom, the body cavity, through schizocoely, where the mesodermal cells split apart to create the coelomic space.
- Deuterostomes: Deuterostomes form their coelom through enterocoely, where the coelomic pouches develop from the archenteron and eventually merge to form the coelomic cavity.
5. Examples:
- Protostomes include animals like flatworms, roundworms, mollusks, and arthropods (insects, spiders, crustaceans).
- Deuterostomes include animals like echinoderms (starfish, sea urchins), hemichordates, and chordates (including vertebrates like fish, amphibians, reptiles, birds, and mammals).
In summary, the main differences between protostome and deuterostome animals lie in the fate of the blastopore, cleavage pattern, mesoderm formation, and the process of coelom development. These distinctions serve as fundamental characteristics used to categorize animals into these two primary divisions.