12-13: Weird Animals

Question 1

What IS an animal? (5 main features)

Answer 1

• Multicellular eukaryote
• No rigid cell wall
• Motile (at least at some stage)
• Heterotrophic
• Blastula (hollow sphere of cells) in development

Question 2

Name the process by which sponges obtain nutrition (and name the cell involved)

Answer 2

Intracellular digestion (phagocytosis) via collar of choanocytes

Question 3

What is the major row involving Ctenophores and Sponges

Answer 3

Which evolved first - there seems to be some evidence for both (sponges first is “simpler” -> parsimony)

Question 4

What is the common feature of all Cnidaria (and what structure is involved)?

Answer 4

Stinging - nematocyst

Question 5

Name the two main current threats to corals

Answer 5

Ocean acidification (formed from CaCO3)
Sea Level Rise (not enough light for zooxanthellae to photosynthesise)

Question 6

Placozoa are considered an ‘enigmatic’ group - what does this mean?

Answer 6

They are difficult to define in terms of existing categories - they are a ‘test’ for our models of animal evolution

Question 7

Define Bilateria

Answer 7

They show left/right symmetry (but NOT dorsal/ventral or head/tail)

Question 8

Are Bilateria diploblastic, triploblastic, or a mix of both?

Answer 8

All Bilateria are triploblastic

Question 9

Define Deuterostomes

Answer 9

Bilateria whose anus develops before the mouth (i.e. blastula becomes the anus)

Question 10

What is different about the totipotency of cells during development between Deuterostomes and Lophotrochozoa/Ecdysozoa?

Answer 10

At the 4-cell stage, Deuterostome cells are still totipotent, whereas in ‘Protostomes’ cell fates are determined following spiral cleavage

Question 11

What is the coelom?

Answer 11

A cavity (often lined by mesoderm-derived epithelium), used in many lineages for making through gut

Question 12

What are the two main groups of non-Deuterostome bilateria?

Answer 12

Ecdysozoa (Moulting Animals) and Lophotrochozoa

Question 13

Which two lineages of Lophotrochozoa are mentioned in detail?

Answer 13

Platyhelminthes (Flatworms) and Molluscs

Question 14

Name the most significant feature of Platyhelminthes

Answer 14

Two nerve cords

Question 15

Name the three groups of Molluscs in terms of feeding strategies

Answer 15

Gatropods (Slugs and Snails -> Includes Grazers, Browsers, Predators)
Bivalves (Filter-Feeders)
Cephalopods (Scavengers and Predators)

Question 16

Name the key feature believed to have been in the Hypothetical Ancestral Mollusc, and name what is has evolved into in cephalopods

Answer 16

Radula -> Beak

Question 17

What structure do molluscs breathe through?

Answer 17

Gill

Question 18

How common are shells in mollusc evolutionary history?

Answer 18

ALL molluscs have a shell, or have lost one

Question 19

Name the four main groups of Arthropods, and the category which encompasses three of them

Answer 19

Chelicerates, Myriapods, Crustaceans, Insects (Latter 3 are all Mandibulata)