Block 4 + 5 - Animal development

Question 1

What are invertebrates?

Answer 1

Not a meaningful group, they have little in common aside from lacking a spine.

Question 2

What is a phylum?

Answer 2

Phenetic:
Animals with fundamentally similar body parts. Different phyla show fundamentally different body plans.

Phylogenetic:
Major clades - based on genetic relatedness

Question 3

What are the 4 fundamental body plasn features?

Answer 3

• Body symmetry (radial vs bilateral)
• Number of germ layers (diplo- vs triploblast)
• Kind of body cavity
• Development fate of blastopore (proto vs deutrostomes)

Question 4

What are the adaptive values of radial and bilateral symmetry?

Answer 4

Radial:
Adaptive for sessile or slow-swimming life style. Food and threats can come from any direction

Bilateral:
Adaptive for life on the move - goes in hand with cephalisation

Question 5

What is a body cavity?

Answer 5

• A fluid filled space between ectoderm and endoderm
• Blastocoel: primary cavty within the blastula
• Coelom: secondary cavity within the mesodermal tissue that is lined with a mesodermal epithelium = peritoneum

Question 6

What is a coelomate?

Answer 6

Have a true coelom, a body cavity completely lined with tissue derived from the mesoderm.

E.g. earthworms

Question 7

What is a pseudoceolomate?

Answer 7

Have a body cavity lined by tissue derived from the mesoderm AND endoderm.

E.g. roundworms

Question 8

What is an acoelomate?

Answer 8

Lack a body cavity between the digestive cavity and outer body wall.

E.g. planarians

Question 9

What is the importance of a body cavity?

Answer 9

• Cushions suspended internal organs
• Decouples growth and movement of organs from outer body wall
• Hydrostatic skeleton

Question 10

What are proifera?

Answer 10

Animals without tissues:
. no nerve cells
. no muscles
. no germ layers
. no organs
. no planes of symmetry

• 5,500 species

E.g. sponges

Question 11

What is the basic form and how do proifera fees?

Answer 11

Filter feeders with no mouth:
Pores for water intake
Osculum = outlet

unidirectional water flow - 1x body volume every 5 seconds

Central cavity = spongoceol
Outside = layer of pinacocytes (pinacoderm)
Inside = choanocytes or collar cells (choanoderm)

Question 12

What are choanocytes?

Answer 12

Flagellum surrounded by a colar or micro milli.
Drive the water current through the sponge.
Food partucles are captured by the colar and phagocytosed

Question 13

What is the body structure of a sponge?

Answer 13

Main body - mesohyl = acellular protein gel matrix with scattered mobile cells

Reinforced by skeletal elements:
- protein fibres: spongin
- mineral spicules: either calcium carbonate (calcite) or sillica

Question 14

Explain the movement of a sponge

Answer 14

• Can slowly change shape
• Can close/ open pores to regulate water flow
• Some can move on substrate: 1-4mm/ day

Question 15

What are eumetazoa?

Answer 15

Distinctive tissues including nerves and muscles.

Gastrulation producces germ layers:
- endoderm; lines gut cavity
- exoderm; covering the outer surface
- +/- mesoderm

Question 16

What are cnidaria?

Answer 16

Metazoa without mesoderm

• 10,000 species
  Mostly marine
• radial
• mouth sirreounded by tentacles; carnivorous (tiny crustaceans)
• no seperate anus
• no brain (diffuse nerve net coordinates movements)
• dipoblastic (but with three layered body wall)
• Epidermis; outer epithelium
• Gastrodermis; inner epithelium (coelenteron)
• Mesoglea; acellular emebrane or jelly-like matrix (not a tissue)

Two body types:
- Polyp - sessile, tube with mouth up, thin mesoglea
. asexual, budding to generate medusa
- Medusa - swimming, umbrella with mouth down, thick mesoglea
. sexual, generates egg and sperm. Planula larva settles and develops into polyp

Main groups:
- Hydrozoa; hydroids (often colonial)
- Scyphozoa; jellyfish (medusoid, solitary)
- Anthozoa; polypoid (coral, sea anemones)

Question 17

What is a cnidocyte?

Answer 17

Unique to cnidarians
- particularly on tenticles

Trigger hair (cnidocil) - fired when touched
- nematocyst: pressurised stinging structure with toxins

Question 18

What are bilateria?

Answer 18

The rest of the animal kingdom

bilaterally symmetrical
with mesoderm (triploblastic)

Question 19

How do you differentiate between tooth types?

Answer 19

• Incisors (I)
• Canines (C)
• Premolars (P)
• Molars (M)

Dental formula:
Upper jaw, carnivore - e.g. I3, C1, P4, M2
Upper jaw, herbivore - e.g. I0, C0, P3, M6

Both jaws e.g. I3/3, C1/1, P4/4, M2/2 (can be summed and multiplied by 2 to give total number of teeth)

Question 20

What are the three major clades of mammals?

Answer 20

1) Monotremes: egg-laying mammals. 5 species
2) Marsupials: with pouch = marsupium. 330 species
3) Placentalia: placenta and umbilical chord. ~5000 species

Question 21

What are monotremata?

Answer 21

• Confined to Australia and New Guinea
• Eggs, but nurse their young with milk
• No teeth as adults:
  . Platypus, Fam. Ornithorhynchidae: 1 species
  . Echidna, Fam. Tachyglossidae: 4 species

Question 22

What are marsupialia (metatheria)?

Answer 22

With marsupium = pouch
- kangaroos and wallabies
- koalas, wombats, opossums

In Australasia, New Guinea and the Americas
- distribution reflects geology at the time of their evolution

Question 23

What are eutheria (placentalia)?

Answer 23

The rest of the mammals and the most diverse clade

Question 24

What are eutheria (placentalia)?

Answer 24

The rest of the mammals and the most diverse clade