21 Sponges, Cnidaria, Ctenos and Deuterostomes

Question 1

grade of body plan

Answer 1

based on body plans and embryonic development
each grade of body plan features shared by the taxa belong to the branch

Question 2

Current hypothesis of animal phylogeny is based mainly on

Answer 2

molecular data
- sequences of ribosomal RNA

Question 3

morphology based phylogeny
- unique to morph phylogeny

Answer 3

indicates two bilaterian clades:
deuterostomes and protostomes
* Assumes that these development modes reflect a phylogenetic pattern
* Arthropods and annelids are grouped
because have segmented bodies

Question 4

unique to molecular phylogeny

Answer 4

indicate three bilaterian clades: Deuterostomia,
Lophotrochozoa , Ecdysozoa
* Arthropods and annelids are not closely related

Question 5

overlap b/w molecular and morphological phylogenetic trees

Answer 5

• All animals share a common ancestor
• Sponges are basal animals
• Eumetazoa is a clade of animals with true tissues
• Most animal phyla belong to the clade Bilateria
• Vertebrates and some other phyla belong to the clade Deuterostomia

Question 6

Lophotrochozoans

Answer 6

share a common characteristic called the lophophore, a feeding structure
- its branch on the tree is solely based on larval form
* Other phyla go through a distinct larval stage
called a trochophore larva

Question 7

Ecdysozoans

Answer 7

share common characteristic: They shed their exoskeletons through a process called ecdysis

Question 8

sponge

Answer 8

= basal animals
-No symmetry
-Spicules
- choanocytes
-Very primitive
- lack true tissues
- asymmetrical
Spicules: are elements found in most sponges that provide structural support, deter predators, also used for identification

Question 9

Eumetazoa

Answer 9

Eumetazoa = animals with true tissues
- basal eumetazoans are diploblastic, generally have radial symmetry
- ex: Cnidaria
and Ctenophora

Question 10

Cnidaria

Answer 10

basic body plan = sac with central digestive compartment, the gastrovascular cavity
- a single opening functions as both
mouth and anus

Question 11

Cnidarians

Answer 11

• Reproduction: “alternation of generations”
• Primarily carnivorous
• Complex intracellular organelles cnidocytes, used for defense or feeding
• Radial* or biradial symmetry
• Tissue-level organization (mesoglea between epidermis and gastrodermis)
• Primitive Nerve net

Question 12

Cnidarian characteristics

Answer 12

Two main forms:
- medusae (pelagic, mobile)
- polyp (benthic, sessile)

Question 13

Cidocytes

Answer 13

Purpose: food capture and protection
- complex intracellualr organelles cnidocytes
(specialized cells that produce nematocysts)
- quickly shoots out barbs into prey and inject toxins
- nematocysts produce toxins

Question 14

nematocysts

Answer 14

inject toxins into prey to paralyze them

Question 15

4 Cnidarian classes

Answer 15

1. Scyphozoa (jellyfish)
2. Hydrozoa (hydra, Portuguese man of war, velella)
3. Cuboza (box jellyfish)
4. Anthozoa (anemones, coral, etc.)

Question 16

Class Scyphozoa

Answer 16

• alternation of generations
• medusae is more conspicuous (obvious) life stage and dominant where it isn’t attached to sea floor (polyp)
• Strobilation occurs and juvenile medusae
  (ephyra) released
  Planula larvae settle and may encyst
• When conditions right, cyst grows
  into a polyp

Question 17

what controls jellyfish population

Answer 17

• Food supply: poised for rapid reproduction
• Environmental conditions: temperature, salinity, etc
• Predators (not many!) include: sea turtles, a few fish, some nudibranchs, other cnidarians and humans

Question 18

Class Hydrozoan

Answer 18

• alternation of generations
• polyp is more conspicuous(obvious) life stage
• passive feeders b/c lure prey by making tentacles look like prey (ex: plankton)
• need strong toxin to immobilize prey so it doesn’t move and tear the jelly apart because its fragile

Question 19

Class Cubozoa

Answer 19

• medusa is cuboidal
• tentacles hang from corners
• polyps reduced or absent
• highly toxic nematocysts
• can eat large fish
• can sense light but not see
  ex: box jelly

Question 20

Class Anthozoa

Answer 20

• anemones, coral
  -it’s benthic which means it is found on ocean floor

Question 21

Phylum Ctenophora

Answer 21

• 2 Identifying characteristics: ctenes, colloblasts
• 8 rows of combs (fused cilia called ctenes) used for locomotion
• tentacles have colloblasts for prey capture
• monomorphic (no sessile life stage)
• biradial symetry
• statocyst on aporal pole
• reproduction: hermaphroditic

Question 22

Phylum Ctenophora
- nervous system and movement

Answer 22

• control of comb rows: apical sense organs
• Distinct features: Eight comb rows, Apical sense organ (statocyst), Tentacles (some)

Question 23

Clade: Bilateria

Answer 23

• bilateral symmetry
• quasi bilateral
• 3 germ layers
• Cambrian explosion = rapid diversification

Question 24

Major Clades of Bilateria

Answer 24

All are invertebrates except for chordata
- Dueterostomia
- Lophotrocozoa
- Ecdysozoa

Question 25

Echinodermata

Answer 25

• Deuterostome
• Identifying characteristic: water vascular system b/c only they have them
• 5 part symmetry
• tube feet function in locomotion, feeding, respiration, waste transport
• digestive tract
• larvae are bilaterally symmetrical

Question 26

6 Classes of Echindermata

Answer 26

sea star
Sea Urchin
sand dollar
sea cucumber
brittle star
sea lilies