Bilateria

Question 1

Bilateria:

Answer 1

• Are triploblastic
• Have body axis organized anterior to posterior
• Tend to have a head region, cephalization

Question 2

Mesoderm

Answer 2

present and specialized
- Muscles, blood, organs
- Forms body cavities (acoel, pseudo, coelomate)

Question 3

Proto-

Answer 3

mouth (proto =) first
- Protostomes contain 23 phyla(!) split into two larger clades: Spiralia and Ecdysozoa - > 1 million spp.

Question 4

Deuterostomes

Answer 4

mouth (deutero =) second
- Deuterostomes now only include: Echinodermata, Hemichrodata and Chordata (US!) – 100,000 spp.

Question 5

Spiralia -

Answer 5

Bilaterians with spiral cleavage, although it has been lost secondarily in one lineage, Lophophorata

Question 6

Ecdysozoa -

Answer 6

• Animals that molt their cuticles for growth
  E.g. Arthropods, nematodes and obscure worms
• Cuticle is non-living outer layer secreted by epidermis
• Undergo process of ecdysis, or molting, under the control of hormone ecdysone

Question 7

Rotifera -

Answer 7

• Unsegmented, blastocoelomate protostomes
• All microscopic and mostly solitary
• Synapomorphies
  
  • Complete gut and modified pharynx called a mastax
  • Adhesive glands on posterior end (“toes”)
  • Protonephridia (excretory system) but no circulatory system
  • Males reduced or absent
  • Eutelic – cell division end early in development

Question 8

Corona -

Answer 8

looks like rotating wheels, a modified pharynx called the mastax with internal jaws (trophi)

Question 9

Elongated with spines (“toes”) and cement gland

Answer 9

allows telescoping, absent in swimming species

Question 10

Hydrostatic skeleton -

Answer 10

• Muscles require medium to shorten and relax
• Antagonistic actions to contract and extend - think biceps and triceps
• Requires:
  1. Cavity with incompressible fluid that transmits pressure changes
  2. Cavity is surrounded by flexible outer membrane that can be deformed
  3. Volume of cavity remains constant
  4. Temporary attachment
  5. Two sets of muscles to act against e/o

Question 11

Ciliary suspension feeding

Answer 11

Through generating current, feed on particulates and small microbes

Question 12

Raptorial feeding

Answer 12

With protrusible mastax and trophi, feed on small animals and plant matter

Question 13

Trapping method

Answer 13

where corona has spines in funnel shape, mastax is reduced

Question 14

Type of gut

Answer 14

Complete gut with extracellular digestion, waste removed by cloaca

Question 15

protonephridia -

Answer 15

Has flame bulbs
kidneys = that empties into bladder and then cloaca

Question 16

Rotifera -

Answer 16

• Most are gonochoristic and parthenogenesis is common
• Males are reduced in abundance, size and complexity (Monogononta) or completely absent (Bdelloidea)

Question 17

Chaetognatha

Answer 17

(Arrow worms)

• Synapomorphies:
  1. Chitinous grasping spines
  2. Complete gut
  3. Centralized nervous system
  4. No specialized respiratory or excretory systems
  5. Hermaphroditic, internal fertilization and direct development

Question 18

Feeding and Digestion

Answer 18

• Sit and wait predators
• Captures food in 1/15 of a second with grasping spines
• Short teeth hold prey during ingestion
  
  • Release paralytic toxins from the vestibule pits

Question 19

Feeding and Digestion -

Answer 19

• Captures food in 1/15 of a second with grasping spines
• Short teeth hold prey during ingestion
  - Release paralytic toxins from the vestibule pits
• Uses lateral and caudal fins to reduce sinking and thrust rates, respectively, during prey capture
• Digestion is extracellular in the intestines

Question 20

Reproduction -

Answer 20

• Simultaneous hermaphrodites
  Ovaries in the trunk
  Testes in the tail

Question 21

spermatophores -

Answer 21

sperm-filled vesicles

Question 22

deuterostome-like

Answer 22

Both mouth and anus form secondarily

Question 23

Rotifera - Bodily Functions beyond eating

Answer 23

Has cerebral ganglion near mastax and sensory bristles and antennae