Lecture 16

Question 1

Evolutionary innovation across animal groups: (6)

Answer 1

• Multicellularity
• Tissues
• Gut
• Mesoderm
• Head
• Segmentation

Question 2

These differ btwn protostomes and deuterostomes (5)

Answer 2

• Nervous system
• Hard skeleton
• Coelom
• Anus
• Circulatory system

Question 3

Protostomes

Answer 3

Blastopore develops into mouth

Ex. Rotifers, Flatworms, Annelid, Molluscs, Nematodes, Arthropods

Question 4

Deuterostomes

Answer 4

Blastopore develops into anus

Ex. Echinoderms, Chordates

Question 5

Who are Deuterostomes?

Answer 5

Echinodermata (starfish), Hemichordatata, exenoturbellida, Chordata (us)

Question 6

What is the initial way to distinguish protostome and deuterostomes? What is wrong with it?

Answer 6

• Embryonic Development (gastrulation)
• Priapulid worms are protostomes but their blastopore develops into anus (a protostome with deuterostome development, exception)
• Priapulids (penis worm): been around since Cambrian

Question 7

Protostomes and Deuterostomes (4)

- Significance? When? Monophyly (2)?

Answer 7

• Two major evolutionary lineages of Bilateria
• Split around the Cambrian (500 MYA)
• Monophyly of protostomes is confirmed by genetic similarities (everything in protostomes group is most closely related to others in that group than anything else. Everything radiated from protostomes descended from one common ancestor)
• Deuterostomes are also monophyletic

Question 8

How to distinguish Deuterostomes from protostomes?

Answer 8

• Circulatory system has ventral heart
• Central nervous system is dorsal
• Hard skeleton is internal

Question 9

Echinoderms “spiny skins”

Answer 9

• 7000 species
• strictly marine
• benthic (bottom dweller)
• Diverse modes of nutrition
• Ex. Sea stars, sea urchins, sand dollars

Question 10

Echinoderms - Hard endoskeleton

Answer 10

• CaCO3 plates
• Continuous growth (plates enlarge and new ones are added)
• covered by thin layer of skin and muscle

Question 11

Echinoderms - Bilateria

Answer 11

Some characteristic go away when larvae becomes adults (Echinoderms larvae is bilateral, then pentaradial)

Question 12

How do echinoderms change their symmetry?

Metamorphosis

Answer 12

• intermediate larval stage grows 3 adhesive arms and suckers
• Original mouth and anus disappear and new mouth reappears on left side
• Transformation from egg to newly formed starfish takes about 2 months

Question 13

Water Vascular system

Answer 13

• System of water-filled tubes - hydrostatic skeleton
• end in “tube feet” (podia) - extend through pores in endoskeleton
  Closed system - except for madreporite (opening of hydrostatic skeleton) that let water in and out

Question 14

Podia

Answer 14

used to locomotion, gas exchange, feeding, excretion

secretes an adhesive material when you pull it off

Question 15

Sexual Reproduction - Echinoderms

Answer 15

• separate sexes
• external fertilization
• Broadcast spawning - at a certain time of year, all eggs and sperm (gametes) are released into water and they come into contact and develop into larvae
• Larvae (planktonic, ciliated arms)

Question 16

Asexual Reproduction - Echinoderms

Answer 16

Regeneration
Arms may be dropped and regenerated to:
- Escape predation
- decrease change of infection spreading, reproduce

Question 17

Parthenogenesis

Answer 17

• does not occur normally; induced
• development of unfertilized egg
• can be induced artificially in sea urchin with salt solution

Question 18

Echinoderm Diversity

Answer 18

• Echinoids, Ophiuroids, Holothuroids, crinoids, asteroids

Question 19

Crinoidea

Answer 19

• Sea lilies and feather stars
• Filter feeders
• Can swim if they are detached from water

Question 20

Ophiuroidea

Answer 20

• Brittle stars (many arm spines, filter-feeders, predators, detritivores)
• Basket stars (branched arms, filter-feeders)

Question 21

Asteroidea: Sea stars

Answer 21

• predatory
• fairly mobile
• evert stomach, secrete enzymes to digest prey and then engulf partially digested prey

Question 22

Echinoidea: sea urchins and sand dollars

Answer 22

Sea urchins

• have many spines, locomotion, defense
• Pincers - defense, cleaning (echinoids and asteroids)
• have aristotle’s lantern for scraping algae off rocks

Question 23

Holothuroidea

Answer 23

• Sea cucumber
• detritivores, scavengers, filter-feeders
• reduced endoskeleton
• give rows of tube feet
• respire by drawing water into anus
• feeding tentacles
• Commensal relationship with pearlfish, pearlfish hides in anus of sea cucumber to escape predators

Question 24

Chordates

Answer 24

• 65000 species
• broad, deep phylogeny of chordates
• include the vertebrates
• deuterostomes (pharyngeal slits)
• Coelomates
• Bilateral symmetry

Question 25

Characteristics unique to Chordates

Answer 25

1. Dorsal Hollow nerve cord
2. Notochord
3. Post-and-tail
   Pharyngeal slits are an ancestral trait of deuterostomes

Question 26

Characteristics common to Chordates

Answer 26

1. Ventral heart
2. Reduced segmentation
3. Segmented musculature (Myomeres - important for being able to generate thrust)

Question 27

Chordates (3)

Answer 27

• Cephalochordates
• Urochordates
• Vertebrates

Question 28

Cephalochordates

Answer 28

• Lancelets
• 30 species
• fish like bodies
• live in sediments as adults
• tropical, shallow marine water
• 1-5 cm
• filter feeders
• adults retain all 3 unique chordates characteristics

Question 29

Urochordates

Answer 29

• 3000 species, 90% tunicates (sea squirts)
• Marine
• Do not retain all 3 unique chordates characteristics as adults
• As adults: 1mm to 60 cm
• Solitary or colonial
• Benthic, sessile
• Filter-feeders
  As larvae: Planktonic, resemble tadpoles

Question 30

Urochordates Life History

Answer 30

• Planktonic Larvae
• Larve settles on its head
• Pharynx enlarges
• head and tail degenerate
• becomes sessile adult (no notochord)

Question 31

Urochordates larvae

Answer 31

all three unique chordates characteristics

Question 32

Urochordates adults

Answer 32

no notochord, enlarge pharyngeal gill slits, no dorsal hollow nerve cord