Midterm 2

Question 1

Bilateria Synapomorphies

Answer 1

Cephalization
Central nervous system
Directional synapses

Question 2

Cephalization

Answer 2

Creation of a head
Most prominent in motile bilateria
Place mouth, sensory organs, and information processing at one end
Often secondarily lost in sessile organisms

Question 3

Bilateria

Answer 3

99% of described animal species
Numerous lifestyles in nearly all environments
Broad diversity of reproductive strategies and lifestyles
Most have strong of along anterior/posterior and dorsal/ventral axes
Mesoderm

Question 4

Eucoelom

Answer 4

Hollow cavities surrounding the gut
Lined with mesodermal epithelium
Our peritoneum is a mesothelium

Question 5

Acoelomorpha

Answer 5

No excretory or vascular system 
No through gut 
Syncytial digestive system 
Hermaphroditic 
Internal fertilization (mutual)

Question 6

Xenoturbella

Answer 6

Share many traits with Acoels
Molecular data tend to put them as sister groups to acoels
Larger than acoels

Question 7

Deuterostomes Synapomorphies

Answer 7

Coelom formed by enterocoely

Pharyngeal gill slits

Question 8

Deuterostomes

Answer 8

Radial cleavage
Usually have pharyngeal gill slits
Well-developed coeloms
Not all animals that have deuterostonous development are within the clade deuterostomia (Deuterostonous development may be a plesiomorphy, or have evolved multiple times)

Question 9

Ambulacraria

Answer 9

Shared features include gene sequences and developmental traits

Question 10

Hemichordata synapomorphies

Answer 10

The body is divided into proboscis, collar, trunk

Stomochords (dorsal extension of pharynx)

Question 11

3 Key species of hemichordates

Answer 11

Enteropnuesta (acorn worm)
Pterobranchia
Grapolites

Question 12

Enteropnuesta

Answer 12

Shallow water, benthic
Burrow in sand and mud
Typically 10-45 cm long, can be 3 m long
Mostly rely on hydrostatic skeleton (stiff branchial skeleton supports pharynx and gills)

Proboscis: move food along, contains their heart/kidney, urine exits here

Cilia move water in and out through gill slits

Lack of sensory organs
Decentralized nervous system
Dorsal and ventral nerve cords connected by rings
Some asexual fragmentation, but mostly sexual- dioecious

Question 13

Pterobranchia

Answer 13

Have tubes attached to adhesive disk (look like multiple ball and chain)

Mostly deep water, sometimes shallow
Sexual production of new colonies
Asexual reproduction- results in colonies with identical zooids (colonies are hermaphroditic however zooids are male and female)

Question 14

Graptolites

Answer 14

Common in the fossil record

Question 15

Echinoderms Synapomorphies

Answer 15

Adults have pentaradial symmetry (5-way symmetry, each 72 degrees apart)
Well developed water vascular systems
Endoskeleton of calcareous ossicles
Mutable connective tissue (allows for altered rigidity)

Question 16

Echinoderms

Answer 16

*highly elaborated coelomic spaces play a central role in the biology of echinoderms

Development: Larvae are biradially symmetrical, adults grow from a rudiment within the larvae

Water vascular system: power tube feet

Variation in (diversity): Water vascular system, endoskeleton, relative size of coelom, digestive system, mode(s) of feeding, site(s) of gas exchange

Question 17

Ambulacra

Answer 17

Primary body radii
Can be a groove (starfish) or a zone (urchins)
Podia (tube feet) associated with ambulacra
Radial canals of WVS associated with ambulacra

Question 18

Crinoidea

Answer 18

Stalked crinoids and mobile crinoids

Perivisceral is essentially a cavity
Crinoids most vibrant in the tropics (many shallow species are nocturnal)

Question 19

Stalked crinoids (sea lilies)

Answer 19

Attached suspension feeders

~100 species, all deep water

Question 20

Mobile crinoids (feather stars)

Answer 20

Mobile suspension feeders (temporarily sessile)
Grasp, release and walk with cirri
Indo-pacific and polar (~600 species)

Question 21

Asteroidea

Answer 21

Starfish 
~1500 species 
Highest diversity in north-east pacific 
Predators or scavengers (Bivalves [clams] are the favored prey) 
5-40 arms 
Up to 1 m across 
Water Vascular System (WVS) 
Tube Feet (chrinoidea: feeding, asteroida: locomotion)