Topic 14: Intro to Bilaterians: Lophotrochozoan worm-like things

Question 1

Clade bilateria have ____symmetry and varying degrees of _____(concentration of neural ganglia at head). They are _blastic

Answer 1

bilateral
cephalization
triploblastic

Question 2

list 1 benefit and 2 issues of the bilateral body plan

what’s the solution?

Answer 2

benefit: muscles have superior pull using solid mesoderm vs mesoglea (jelly)

issues:

1. organs cannot move freely
2. difficult to move nutrients from gut to body wall (further distance, many layers)

Solution: coelom!

Question 3

____ develop from the mesoderm

Answer 3

organs

Question 4

What are the advantages of having a true coelom? Select all that apply

a. cushions organs from hard blows
b. allows body to twist without twisting organs
c. allows for more complicated forms of locomotion

Answer 4

all of them are correct

Question 5

the coelom doesn’t need __ etc, but can facilitate the movement of ___

Answer 5

O2

waste (including O2)

Question 6

organ systems allow organisms to be much ___

Answer 6

bigger

more efficient!

Question 7

List 2 advantages of a coelom

Answer 7

1. hydrostatic skeleton: more effective than skeletal support
   - fluid filled cavity provides more rigid structure than mesoderm for muscles to pull against
2. circulatory system:
   - absorbed nutrients can be circulated around the body
   - wastes can be carried to body surface more easily

Question 8

list 2 results of the coelom

Answer 8

1. faster locomotion

2. larger body size possible (avoid –> become predators)

Question 9

What are the 3 classes of the clade lophotrochozoan to know?

Answer 9

1. Platyhelminthes
2. mollusks
3. Annelida

Question 10

lophotrochozoan clade is ___phyletic and are protostomes, so their first invagination is the ___

Answer 10

polyphyletic

mouth

Question 11

Platyhelminthes have no_____ and are __blastic

Answer 11

coelom (acoelomate)

triploblastic

Question 12

how do Platyhelminthes breathe without a gas exchange system?

Answer 12

diffusion

Question 13

Platyhelminthes have ___ symmetry

Answer 13

bilateral

Question 14

some examples of Platyhelminthes include:

Answer 14

flatworms, tapeworms, parasites w/ 2 suckers

* recognize the diverse phylum w/ unique traits within each group!

Question 15

all lophotrochozoan have a pair of ___ ___ cords

Answer 15

ventral nerve cords

Question 16

what limits the size of Platyhelminthes?

Answer 16

their delivery systems (O2/ nutrients/ waste removal)

Question 17

Annelids are __ worms

They are Eucoelomates. What does this mean?

Answer 17

segmented

• body cavity lined w/ mesodermally derived tissues
• hydrostatic skeleton

Question 18

Annelids have a ___ (open/ closed) circulatory system and exchange gases via ___

Answer 18

closed

skin

Question 19

Annelids have a complete ___ system (with an ___)

Answer 19

digestive

anus

Question 20

Oligochaetes are a class of Annelida who are ____. They transfer sperm by __ and fertilization is ___(ex/internal)

Answer 20

hermaphrodites
copulation
external

Question 21

Mollusks include:

Answer 21

snails, clams, squid, etc

Question 22

mollusks have a ___ ____ made of calcium carbonate enclosing the soft body
- this is lost or reduced in many taxa!

Answer 22

calcareous shell

Question 23

List 4 characteristics of mollusks

Answer 23

1. Mantle: thin layers of tissue that secretes shell
2. muscular ventral foot used for movement
3. organs contained in a visceral mass above foot
4. mouthparts a straplike rasping organ called a radula

Question 24

Mollusks have ___ for gas exchange (and sometimes feeding) and a(n) ___(open/ closed) circulatory system

Answer 24

gills

open