Choanoflagellate
Animal (Metzoan) Origins
• The Major - two cell layer - Phyla Porifera
and Cnidaria
• Minor phylum Placazoa, Relationships
within Porifera and the origins of Metazoa
http://www.redrae.addr.com/friday/Choanoflagellates.gif
Porifera
Million years ago
• Marine except for one freshwater group
• Cellular rather than tissue level of organization
(no separation of somatic from germ tissue)
• Water canal system
• Water and food moved through whole animal
using flagellated choanocyte cells (layer of
protective cells on exterior and amoebocyes that
move through jelly layer that, along with internal
skeleton, is needed for support)
100
Cretaceous-Tertiary
200
300
400
500
600
End-of-Permian
(90+% of spp lost)
1st vertebrates on land
Ordovician
Cambrian
Oldest-known fossils (Ediacara fauna)
700
800
900
Evidence of Porifera 1.8 billion years BP
in sponge-specific “chemofossil”
Larvae are free swimmers
From UTM BIO 152 Website
From UTM BIO 152 Website
1
Adults are
sessile
From UTM BIO 152 Website
Phylum
PORIFERA
Class: Hexactinellida
(glass sponges)
Classes
• Hexactinellida
• Demospongiae
• Calcarea
From UTM BIO 152 Website
Calcarea
http://bioweb.uwlax.edu/zoolab/Table_of_Contents/Lab-3a/Calcarea/Lab_3a-01a.jpg
2
Placozoa
Ctenophora
http://trc.ucdavis.edu/biosci10v/bis10v/week9/
placozoa.gif
http://www.virtuallaboratory.net/Biofund
amentals/lectureNotes/AllGraphics/trich
olast.jpg
From the Tree of Life: A lack of resolution of
relationships among basal phyla
Dawkins
Bilateria
Cnidaria
http://www.tolweb.org/Animals/2374
Ctenophora
Placozoa
Porifera
Choanoflagellates
Dellaporta et al (2006) PNAS 103: 8751-8756
(Baysian analysis of MtDNA genome)
Porifera
Molecular characters and some fossil evidence (Botting & Butterfield (2005)
PNAS 102: 1554-1559) conclude that poriferans are paraphyletic
Porifera
Ctenophora
Cnidaria
Hex & Des Calc
The rest (Eumetazoa)
Placozoa
Placozoa
Choanoflagellates
Bilateria
Choanoflagellates
3
Cnidaria
From UTM BIO 152 Website
nematocyst
Class: ANTHOZOA
http://www.divegallery.com/coral_cl
oseup.htm
Class: CUBOZOA - Box jellyfish
Scyphozoa
Jellyfish movie male
http://library.thinkquest.org/C007974/2_1bo
x.htm
4
Colonial hydrozoans
Class: HYDROZOA
- Hydra Hydrozoa
From UTM BIO 152 Website
From UTM BIO 152 Website
//intergate.sdmesa.sdccd.cc.ca.us/ilc/biology/plankton/ima
Man-of-war
http://www.key-biscayne.com/beach_park/facts/manowar.shtml
5