Metazoa & Placozoa

Question 1

characteristics of animalia

Answer 1

• multicellular
• lack cell wall
• chemoheterotrophic
• mostly sexual (motile haploid sperm, larger non-motile haploid)
  animate : move entire body in at least one stage of life.

Question 2

synapomorphies of animals

Answer 2

• gastrulation + embryonic tissue layers
• unique types of intercellular junctions
• type 4 collagen
• basal lamina
• striated myofibrils & actin-myosin contractile elements

Question 3

define anisogamy

Answer 3

haploid gametes of different sizes

Question 4

gastrulation + embryonic tissue layering

Answer 4

cleavage = mitotic cell division without grows of cells between divisions.
blastula (hollow ball) undergoes gastrulation.
direct development or indirect development

Question 5

cleavage =?

Answer 5

mitotic divisions without growth of cells btw division

Question 6

blastula?

gastrulation?

Answer 6

hollow ball of cells formed

- when blastula invaginates.

Question 7

direct development vs indirect development

Answer 7

direct = embryo looks like mini adult
indirect = one or more intermediate (larval) stages. morphology and behaviour differs from sexually mature adult.

Question 8

what are intercellular junstion?

Answer 8

specialized area of contact.

adhere and interact.

Question 9

3 main functions of intercellular junctions?

Answer 9

1. barrier - create concentration gradient
2. cell-cell adhesion
3. intracellular communication via ion exchange

Question 10

type 4 (IV) collagen - allows for?

Answer 10

allows for cells to stick together and work together

Question 11

basal lamina
- what is it?
main constituent?

Answer 11

• epithelium secreted layer of basement membrane

- collagen IV is main constituent.

Question 12

HOX genes -
control what development?
absent in?

Answer 12

control anterior to posterior development sequence of embryos.
absent in sponges, placozoans and ctenophores.

Question 13

Phylum placozoa

Answer 13

6-striated ciliary rootlets. 
- small body, 
2 epithelium-like layers. 
lacks anterior-posterior polarity, mouth.gut, NS or muscle. locomotion w cilia
repro w fission, maybe sexual 
feeding extracellular digestion

Question 14

striated myofibrils + actin-myosin contractile elements

Answer 14

some lack mesodermally derived muscles. use contractile elements to move bodies without muscle