Topics 14-16

Question 1

What are homeobox and hox genes?

Answer 1

• homeobox: highly conserved nucleotide sequence with regulatory genes
• hox-genes: control the anterior and posterior developmental sequence of the embryo

Question 2

What is the clade Bilateria?

Answer 2

• bilateral symmetry
• varying degrees of cephalization
• triploblastic

Question 3

What is the benefits and issues to the evolution of body plans?

Answer 3

benefits: muscles have superior pull using solid mesoderm vs. mesoglea
issue: organs can’t move freely and difficult to move nutrients from gut to body wall

Question 4

What is the solution to the body plan issues?

Answer 4

• body cavity = coelom
• organs bathed in fluid
• movement doesn’t squeeze organs
• organs can grow within the space
• diffusion of nutrients/waste is easier

Question 5

What are the advantages of coelom?

Answer 5

• faster locomotion
• hydrostatic skeleton
• circulatory system

Question 6

What is the clade Lophotrochozoa?

Answer 6

• polyphyletic group
• very unique animal types (simple->complex) what do they share? -> protosome development and unique molecular characters

Question 7

Describe the Phylum Platyhelminthes

Answer 7

• flatworms
• acoelomate
• no special circulatory or gas-exchange system
• bilateral symmetry (cephalization)

Question 8

What are the three classes of interest in the Phylum Plathelminthes?

Answer 8

• turbellaria (free-living flatworms)
• cestoidea (endoparasitic tapeworms)
• trematoda (parasites with two suckers)

Question 9

Describe the Phylum Annelida

Answer 9

• segmented worms
• eucoelomate
• closed circulatory system
• gas exchange via skin
• complete digestive system with anus
• excretory & nervous system

Question 10

Describe the Phylum Mollusca

Answer 10

• snails, clams, mussels, squid, octopus
• highly adaptive body plan
• 2nd only to arthropods
• mostly calcareous shell enclosing soft body
• shell lost or reduced in most taxa
• muscular foot for movement
• open circulatory system