lec 10

Question 1

except for
Xenacoelomorpha,
the Bilateria is
divided into two
large clades:

Answer 1

Deuterostomia
and Protostomia

Question 2

all bilateria except xenacoelomorpha
what supports this?

Answer 2

Nephrozoa
unique family of hox genes

Question 3

what differs b/w protostome and deuterostome

Answer 3

1) origins of mouth and anus
2) origin of eucoelom
3)cleavage
4) # cilia

Question 4

how do origins of mouth and anus differ? dogma

Answer 4

blastospore gives rise to:
mouth in Protostomia
-the anus arises secondarily
anus in Deuterostomia
-the mouth arises
secondarily

Question 5

origin of eucoelom differing how?

Answer 5

Protostomia: solid mesoderm ‘splits’ to form schizocoely
Deuterostomia: pockets from embryonic gut cavity close
off and form enterocoely

Question 6

schizocoely

Answer 6

mesodermally
lined coelom

Question 7

enterocoely

Answer 7

enclosed, mesodermally lined coelom

Question 8

how does cleavage differ? dogma

Answer 8

Protostomia it is spiral and determinate
Deuterostomia: cleavage is radial and
indeterminate

Question 9

how does number of cilia differ? dogma

Answer 9

multiciliated cells in Protostomia
monociliated cells in Deuterostomia

Question 10

truth abt mouth origin

Answer 10

-Deuterostomia do follow the
‘mouth second
-only some protostomia are mouth first

Question 11

truth abt ciliation

Answer 11

monociliation is common in deuterostomes and rare in protostomes there are still exceptions

Question 12

Protostomia

Answer 12

dorsal cerebral
ganglia form circumesophageal
connectives to ventral nerve cords

Question 13

clade spiralia

Answer 13

-Lophotrochozoa
-many, but not all show spiral cleavage
-

Question 14

spiral cleavage

Answer 14

-the first cleavages produce cells
slightly offset
-determinate cleavage–> each cell has predefined fate
-no identical twins

Question 15

indeterminate

Answer 15

cell specialization
happens much later, and early twinning is possible

Question 16

Phylum Platyhelminthes

Answer 16

considered basal
among the protostomes
30,000 spp
flattened in form

Question 17

what protostome features do they lack

Answer 17

-no coelom or circ system
-blind gut–> no anus
-simple ladder like nervous system w anterior brain

Question 18

what does platyhelminths nervous system lack

Answer 18

circumoesophageal connectives

Question 19

features common to most flatworms

Answer 19

1 active excretion by network of protonephridia
2. tremendous capacity for regeneration &
asexual reproduction
3. hermaphroditic with internal fertilization
4. development is direct, without distinct larval stage
5. ectolecithal

Question 20

ectolecithal

Answer 20

yolk is
on the outside of the fertilized egg

Question 21

neoöphoran

Answer 21

-the yolk can go around a single
fertilized egg that is then surrounded
by an egg capsule
-several eggs can be surrounded by
yolk in a single capsule

Question 22

entirely parasitic platyhelminth groups, monophyletic?
what are the rest placed in? monophyletic?

Answer 22

Trematoda, Monogenea Cestoda- probably monophyletic
the rest placed in class Class Turbellaria
paraphyletic