How do these taxa relate?. How do these embryological features relate to Deuterostomes and Protostomes?

How do these taxa relate?

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How do these embryological features relate to Deuterostomes

and Protostomes?

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Basal DeuterostomesHaeckel 1874, proposed phylum “Chordata” and 3 subphyla:

______________

______________

______________ (includes Hagfish)

Basal DeuterostomesHypothesis that vertebrates and these “protochordates” share common ancestor provides impetus for study

What features do these larvae share?

How are they unique?

Basal Deuterostomes_____________ (sea stars and allies)

In fossil record from Cambrian to present

____ classes… today representatives of ___

Unique features:

*

*

So why would they be considered “more closely related” than other marine invertebrates… say clam worms?

http://www.palaeos.com/Invertebrates/Deuterostomia/Homalozoa/Images/Syringocrinus.gif

Basal Deuterostomes_________________ (acorn worms)

Bateson 1884, proposed Hemichordata as a subgroup of _____________

http://www.wildsingapore.com.sg/wildfilms/blog/050402cjd2070m3a.jpg

http://coris.noaa.gov/glossary/hemichordate_186.jpg

Basal DeuterostomesHemichordata (acorn worms)

2-3 possibilities for taxonomic placement:

*

*

* http://www.geol.umd.edu/~tholtz/G331/lectures/331grapt.html

Basal DeuterostomesFeatures shared by echinoderms and hemichordates:*Similar ciliated larvae (________ and _______)

*

*

Features linking to chordates:

*

*

http://scaa.usask.ca/gallery/lacalli/images/tornaria3.jpg

http://scaa.usask.ca/gallery/lacalli/images/cucumber5.jpg

UrochordatesFilter-feeding marine organisms divided into 3 classes:

*____________ (tunicates or “sea squirts”)

*

*

Adults respire and feed using:

* *

__________sends food to _________, then __________

http://www.youtube.com/watch?v=mecEpYS2Bgw

UrochordatesFilter-feeding marine organisms divided into 3 classes:

*__________________

Free-swimming plankton

Large mucus tunic

http://homepage.mac.com/a.shiroza/pictures/planktons/bwttf/larvatian1p2_x50.jpg

UrochordatesFilter-feeding marine organisms divided into 3 classes:

*____________ (“salps”)

Alternation of generations (free-living and colonial)

No notochord… so why in phylum chordata?

http://www.youtube.com/watch?v=KRVdGam3G2U&NR=1

http://chemistry.csudh.edu/faculty/jim/cantamar/salp.jpg

Cephalochordates*

2 genera:*Branchiostoma *Asymmetron

*

http://comenius.susqu.edu/bi/202/Animals/DEUTEROSTOMES/cephalochordata/uwinnipeg-Lancelet.jpg

CephalochordatesBrief survey of systems:

Musculature and integument:

*

*

*

*

*

*

Advantages of thin skin?

CephalochordatesPharyngeal slits:

Exit to …

Filtered water leaves via …

…minimizes respiratory usefulness

Cephalochordates“Skeletal” Notochord:

__________________more apropo

*

*

Notochord to rostrum adaptation for …

Other “skeletal” elements include:

CephalochordatesNervous system

*

*(38 vs. 10-18)

Spinal nerves with ___________ onlyconducting sensory (afferent) signals to spinal cord and brain

*

CephalochordatesDigestive system

*

Buccal cirri coarse filter, monitor water

Vestibule bounded by oral hood and velum

*

*

Ciliated cells create …

Moves to midgut to mix with …

Intestinal cecum …

CephalochordatesCirculatory system

*

*

*

Cecal vein assists by pumping to sinus

CephalochordatesExcretory system

*

Cryptopodocytes (between protonephridia and podocytes)

*

*

Wastes leave via…

CephalochordatesReproductive system

*

Gonads (ovaries and testes)empty sex cells (eggs and sperm) into …

CephalochordatesCompare - Contrast

No

No

No

2 instead of 3

2 layered skin (1 cell thick)

No

Greatly reduced coelom

BUT many synapomorphies

Origin of craniates