Bilateria

Question 1

Emerging patterns of Bilateria

Answer 1

1. Bilateral symmetry
2. Opposing muscle layers
3. Efficient feeding & digestion
4. Coelom
5. Hemal system
6. Excretory system

Question 2

What is the one plane of symmetry possessed by organisms with bilateral symmetry?

Answer 2

Midsagittal

Question 3

Bilaterians possess ___ plane of symmetry

Answer 3

One

Question 4

Bilaterians possess ___ primary axes

Answer 4

Three

Question 5

What are the three primary axes possessed by organisms with bilateral symmetry?

Answer 5

1. Anterior-posterior
2. Dorsal-ventral
3. Distal-proximal

Question 6

The anterior-posterior axis is ___-___

Answer 6

head-tail

Question 7

The dorsal-ventral axis is ___-___

Answer 7

back-belly

Question 8

The distal-proximal axis is ___-___

Answer 8

body-limb

Question 9

What are the advantages of bilateral symmetry?

Answer 9

1. Increased rate of encountering resources when experiencing horizontal gradients
2. Efficient search for resources (food, mates, etc.)

Question 10

What is the primary consequence of bilateral symmetry?

Answer 10

Cephalization of sensory structures

Question 11

Bilateral symmetry and cephalization are most prominent in what kind of bilaterians?

Answer 11

Bilaterians that live in strong horizontal gradients

Question 12

Bilateral symmetry and cephalization are most prominent in what kind of bilaterians?

Answer 12

Bilaterians that are sessile filter feeders

Question 13

Many bilaterians that are sessile feeders possess ___ ___ symmetry

Answer 13

secondary radial

Question 14

Some organisms that possess secondary radial symmetry

Answer 14

1. Bryozoans
2. Echinoderms
3. Some worms

Question 15

One of the emergent patterns of bilateria is the presence of opposing muscle layers. Explain.

Answer 15

Circular and longitudinal layers enable controlled hydrostatic deformation

Question 16

In bilaterians, (1)___ ___ of opposing muscle layers allows for more efficient (2)___

Answer 16

1. peristatic coordination

2. burrowing

Question 17

What is possessed by bilaterians that allows for the emrgence of more efficient feeding and digestion?

Answer 17

1. Complete digestive tract (gut)
2. Both mouth and anus
3. Increased consumption and assimilation

Question 18

Coelom

Answer 18

A fluid-filled internal cavity or canal lined by a mesdoerm-derived epithelium

Question 19

What is possessed by all large bilaterians?

Answer 19

A coelom

Question 20

Coelomate

Answer 20

An organism possessing a coelom

Question 21

What is absent or difficult to detect in some small bilaterians?

Answer 21

A coelom

Question 22

Functions of the coelom:

Answer 22

1. Additional internal compartment for specialization and regulation
2. Hydrostatic skeleton
3. Internal transport
4. Excretion
5. Reproduction

Question 23

Hemal system

Answer 23

A connective-tissue compartment that circulates fluid (blood)

Question 24

“Closed” hemal system

Answer 24

entirely contained in blood vessels

Question 25

"Open" hemal system

Answer 25

some vessels ultimately opening to a hemocoel

Question 26

In a hemal system, what circulates blood?

Answer 26

Muscles

Question 27

In a hemal system, blood may contain what?

Answer 27

Respiratory pigments

Question 28

What are the functions of a hemal system?

Answer 28

1. Respiratory 2. Circulatory 3. Excretory

Question 29

Excretory system

Answer 29

Removes metabolic waste

Question 30

What is the excretory organ in small bilaterians?

Answer 30

Protonephridia ("flame bulb")

Question 31

What is the excretory organ in larger bilaterians?

Answer 31

Metanephridia

Question 32

Divisions between Protostome and deuterostomes: cleavage

Answer 32

D: Radial P: Radial, spiral, or bilateral

Question 33

Divisions between Protostome and deuterostomes: blastopore fate

Answer 33

D: Blastopore becomes anus; "second mouth" P: Blastopore becomes mouth/mouth and anus; "first mouth"

Question 34

Divisions between Protostome and deuterostomes: coelom formation

Answer 34

D: Enterocoely P: Schizocoely

Question 35

Cleavage patterns: Radial

Answer 35

1. Equal perpendicular division of cells | 2. Regulative cell fate (cell develops according to placement in embryo)

Question 36

Cleavage pattern: Spiral

Answer 36

1. Unequal offset division of cells | 2. Determinate cell fate (cell fate determined by contents)

Question 37

Schizocoely

Answer 37

The coelom forms from splitting of the mesoderm

Question 38

Enterocoely

Answer 38

The coelom forms from out-pocketing of the gut

Question 39

Generalizations about large organisms: Gut

Answer 39

Complex, one way

Question 40

Generalizations about large organisms: Coelom

Answer 40

Present

Question 41

Generalizations about large organisms: Hemal system

Answer 41

Complex, often with a heart

Question 42

Generalizations about large organisms: Gas exchange

Answer 42

Complex, with gills, O2 carrying proteins, etc.

Question 43

Generalizations about large organisms: Excretion

Answer 43

Metanephridia

Question 44

Generalizations about small organisms: Gut

Answer 44

Simpler, sometimes blind (no anus)

Question 45

Generalizations about small organisms: Coelom

Answer 45

Reduced or absent

Question 46

Generalizations about small organisms: Hemal system

Answer 46

Reduced or absent

Question 47

Generalizations about small organisms: Gas exchange

Answer 47

Simple, diffusion-based

Question 48

Generalizations about small organisms: Excretion

Answer 48

Protonephridia or diffusion-based