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Branches on the Tree of Life – Evolution of the Animal Phyla
Sponges
Cnidarians
Acoel Flatworms
Echinoderms
Chordates
Arthropods
Nematodes
Flatworms
Molluscs
Annelids
6
5
Tornaria Larva
Trochophore Larva
3
4
1 – Common ancestor to all bilateral animals
Larva with blind gut
2 – Development genes for segmentation and
photoreception added to the genetic toolkit
2
3 – Deuterostome Line
4 – Protostome Line
5 – Ecdysosomes (molting animals)
1
6 – Lophotrochozoans
Animal Phyla Evolved More Than 500 Million Years Ago
All animal phyla
descended from
a protist ancestor
similar to this modern
choanoflagellate.
These photographs show 6 of the 13 phyla found in Burgess Shale rocks dated at 510 – 520 mya.
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Sponge
Brachiopod
Chordate
Arthropod
(Wapkia)
(Nisusia) (Pikaia)
(Marella)
Mollusc Annelid
(Scenella) (Wiwaxia)