Summary
Two animal lineages differing in embryonic development; deuterostomes include echinoderms and chordates.
In depth
In protostomes, the blastopore becomes the mouth and cleavage is spiral and determinate; in deuterostomes, it becomes the anus and cleavage is radial and indeterminate (identical twins possible).
Early development differs in cleavage and fate. Molecular data support the groups.
Example: humans are deuterostomes, as are sea urchins.
Protostomes ("first mouth") include annelids, molluscs and arthropods and nematodes, and are divided into Lophotrochozoa and Ecdysozoa. Deuterostomes ("second mouth") include echinoderms, hemichordates and chordates. Further differences: radial and indeterminate cleavage in deuterostomes means that cells keep developmental potential, so a separated cell can produce a whole embryo, which is how identical twins form and why embryonic stem cells are possible.
Molecular phylogenies support these groups and reveal exceptions. Features of the nervous system also differ: protostomes have ventral nerve cords and deuterostomes dorsal. The shared ancestor of bilaterians possibly lived over 600 million years ago.
Key idea: our own mouth forms after the anus, from a second opening, showing our deuterostome origin.
Frequently asked questions
What is Protostomes and Deuterostomes?
Two animal lineages differing in embryonic development; deuterostomes include echinoderms and chordates.
Which area of biology covers Protostomes and Deuterostomes, and how advanced is it?
Protostomes and Deuterostomes is one of the 53 topics in Zoology & Animal Diversity. It is rated Intermediate, so it suits learners who already know the core vocabulary. Related topics in this area include Animal Phylogenomics, Animal Kingdom, Vertebrates and Invertebrates.
Can you give an example of Protostomes and Deuterostomes?
Molluscs, annelids and arthropods are protostomes.
What should I learn before Protostomes and Deuterostomes?
Work through the Beginner topics in Zoology & Animal Diversity first, such as Animal Kingdom, Vertebrates and Invertebrates, Sponges, then return to Protostomes and Deuterostomes. Intermediate topics assume the Beginner vocabulary.
What topics are related to Protostomes and Deuterostomes?
The closest topics to Protostomes and Deuterostomes are Animal Phylogenomics, Animal Kingdom, Vertebrates and Invertebrates, Body Cavities. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Protostomes and Deuterostomes?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Protostomes and Deuterostomes. To practise the whole of Zoology & Animal Diversity, use the Zoology & Animal Diversity quiz.
How is Protostomes and Deuterostomes different from Animal Phylogenomics?
Protostomes and Deuterostomes: Two animal lineages differing in embryonic development; deuterostomes include echinoderms and chordates. Animal Phylogenomics: Genome-scale data resolve deep animal relationships, such as ctenophores versus sponges as sister group. Read both side by side and note what each one explains.
How should I study Protostomes and Deuterostomes step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Animal Phylogenomics and explain the difference aloud. Finally, take the Zoology & Animal Diversity quiz and come back to this page for any question you miss.