Humans belong to the phylum Chordata, which includes all animals that possess a notochord at some stage in their development. The phylum most closely related to Chordata is actually the phylum Echinodermata. While these two groups may seem vastly different, they do share some interesting features and also have significant differences.
Shared Features:
- Deuterostome Development: Both Chordata and Echinodermata are part of the deuterostomes, which means that during their embryonic development, the anus forms before the mouth. This is a key feature that unites these two phyla.
- Similar Gene Expression: Molecular studies have shown that certain genetic sequences and developmental pathways are conserved between echinoderms and chordates, indicating a common evolutionary ancestor.
Differences:
- Body Symmetry: A major difference between these two phyla is body symmetry. Chordates, including humans, exhibit bilateral symmetry (where the left and right sides of the body are mirror images), whereas echinoderms typically exhibit radial symmetry (symmetry around a central axis), especially in their adult forms.
- Notochord Structure: While both groups have a notochord at some point during development, in chordates this structure often develops into the vertebral column (spine), providing support and protection for the spinal cord. Echinoderms, on the other hand, do not develop a backbone and have a more rigid endoskeleton.
- Habitat and Mobility: Chordates are primarily bilateral and can be found in diverse habitats, ranging from terrestrial to aquatic environments. Echinoderms are usually marine animals that often move in a more limited manner due to their unique body structure.
In summary, while humans and echinoderms share some embryonic and genetic similarities, their differences in body structure, symmetry, and lifestyle highlight the diverse paths of evolution that these two phyla have taken.