Lecture 4 Pt. 1

Question 1

Placozoan body plan

Answer 1

• The simplest morphological metazoan
• Asymmetrical flattened body
  
  • About 3mm diameter
  • Mostly transparent

Question 2

Distinct epithelial layers

Answer 2

Upper (dorsal)
Lower (ventral)
Extracellular desmosomes

Question 3

Epithelial

Answer 3

The thin tissue forming the outer layer of a body’s surface and lining the canal and other hollow structures

Question 4

Inner space

Answer 4

Mesenchyme
- No guts, nerves, or muscles

Question 5

Epithelial distinctions
Cells of the upper epithelium

Answer 5

• Mono-ciliated, squamous epithelial cells
• Extracellular ‘shiny spheres’

Question 6

Epithelial distinctions
Cells of the lower epithelium

Answer 6

• Mono-ciliated, columnar epithelial cells
• Non-ciliated variations = gland cells

Question 7

Fibre cells

Answer 7

• Mesenchyme fibre cells connected to each other (syncytium)-like as an internal network to mesenchyme
• Microtubule and. microfilament connect other cells with fibre cells

Question 8

Other mesenchymal cells

Answer 8

1.) Crystal cells: sensory function
2.) Ovoidal cells: possibly transitioning/stem cells

Question 9

Ciliated cells

Answer 9

• Help with movement
• Help to eat (phagocytosis)

Question 10

Fission

Answer 10

• Asexual reproduction
• Duplicates its DNA then divides into two parts with each new organism receiving one copy of the DNA

Question 11

Nodding

Answer 11

• Asexual reproduction
• Release of multicellular flagellated bodies from upper dorsal epithelium
• Each ‘swarmer’ becomes an individual

Question 12

Statocytes

Answer 12

Gravity sensing cells in higher plants. Contain amyloplasts - statoliths - starch - filled amyloplastic organelles - which sediment at the lowest part of the cells