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Invertebrate Biology > Quiz 2 - Bilaterians > Flashcards

Quiz 2 - Bilaterians Flashcards

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1
Q

What are bilaterians called

A

Triploblast animal neither a proto nor a deuter

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2
Q

What is metamery

A

Mesodermal event

Serial repetition of unit subdivisions of ectoderm and mesoderm

NOT endoderm

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3
Q

What animals show metamery in bilaterians

A

Annelids
Arthropods
Chordates

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4
Q

What is the step-by-step hypothesis of bilaterian evolution

A

Planuloid-acoeloid hypothesis

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5
Q

What is the archicoelomate hypothesis

A

Fast transition to complex, but then simpler things lost those traits later on

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6
Q

What are 4 possible urbilaterians?

A

Micro, acoel, turbellarian-like worm w cilia locomotion + direct dev

Micro, acoel or pseudo, pelagic

Macro, coelomate, benthic + segmented larva stage

Micro larva w cilia + macro adult coelo w filter feeding adult

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7
Q

What are the 5 bilaterian innovations

A

Bilateral symmetry

Third tissue layer - triploblasts

Compartmentalization

Excretory organs

Complete through gut

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8
Q

If bilateral symmetry came from a benthic form, then it would pre-date the origin of directed locomotion - what is the alternative hypothesis for bilateral symmetry in bilaterians

A

Bilateral symmetry evolved to make internal circulation better by compartmentalizing the gut and major ciliary tracts

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9
Q

What tissue layers contains the GI tract, auditory, respiratory ?

A

Endoderm

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10
Q

What tissue layer contains the mesenchyme, muscles, cartilage, bone, blood + tissue layers?

A

Mesoderm

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11
Q

What is mesenchyme

A

Connective tissue + lymphatic + circulatory system (lymph + blood)

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12
Q

What tissue layer is the nervous system of bilaterians in?

A

Ectoderm

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13
Q

Why did bilaterians require compartmentalization

A

Large body size + extensive mesoderm needed internal fluid filled cavities that are enclosed + controlled

House gonads + locomotion control

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14
Q

Large body size + extensive mesoderm required a good excretory system. Explain ultrafiltration, reabsorption, and transport in bilaterian excretory systems

A

Ultrafiltration - across basal lamina (point of aatached for other cell types + permeability barrier for urine)

Reabsorption - ions + valuable biomolecules

Transport - move waste out of body

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15
Q

What is a complete through gut

A

Mouth and anus

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16
Q

Acoelomate have no body cavity, which means their organs are in direct contact with the epithelium… but what holds the organs in place?

A

Semi-solid mesodermal tissues btw the but and the body wall

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17
Q

Pseudocoelomate are called false cavities… how are they organized

A

Tissue from mesoderm partially line fluid filled body cavity

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18
Q

True coelomates = eucoelomates - with a complete lining called the… ?

A

Peritoneum

Organs are completely attached

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19
Q

Libbie hymans idea about body cavities and complexity ?

A

Difference btw body cavity grades does NOT reflect complexity

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20
Q

What are phylum xenacoelomorpha

A

Acoel
Marine sediments, some can swim
No gut, no excretory system, extracellular matric

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21
Q

Why are xenacoelomorphs thought to maybe be the first bilaterian

A

Acoel - no cavity

No gut, no excretory system, extracellular matrix

Has nerve net + statocysts - early nervous system

No mouth or pharynx - needs endosymbionts like green algae

Fewer than 8-10 hox genes - more similar to bilaterians than cnidarians - thought to be have duplicated before proto/deuter split

22
Q

Who is the wanderer of the phylogenetic tree

A

Xenoturbella

23
Q

Describe xenoturbella

A

Free living, yellow worm, flattened ventrally

A-P + D-V axis, longitudinal grooves

24
Q

Name all the phyla that xenoturbella has been placed under in the phylogenetic tree

A

Acoelomorpha bc simple body plan + cilia

Hemichordata + echinoderm - nerve net + epidermal ultra structure

Was under mollusc but because it consumed eggs of bivalves

25
Q

Why were xenoturbella classified with mollusks

A

Found similar dna, but it was because xenoturbella eat molluscs, so contaminated dna

26
Q

What do hox genes determine

A

Anterior posterior axis

27
Q

How do xenoturbella hox genes compare to the hypothetical proto/deuter ancestor

A

Fewer hox genes

28
Q

Why is xenoturbella significant for determining bilaterian evolution

A

Help explain bilaterian symmetry and mesoderm

29
Q

Whats the second possible bilaterian ancestor

A

Myxozoa

30
Q

Whats the difference between endo and extoparasites

A

Endo - live within another organism

Ecto - live on another organism

31
Q

Parasites are simple and degenerate possibly evolving towards reduced structural complexity

What are the closest free living relatives to parasites - who has the most described parasitic species

A

Nematoda and arthropoda

32
Q

What is the third possible bilaterian ancestor

A

Orthnectida

33
Q

What phyla are endoparasites of turbellarians, polychaetes, gastropods, molluscs, brittle stars

A

Orthonectida

34
Q

Why would orthonectida be possible ancestors of bilaterians?

A

Endo parasitic
Bilateral in some development stages
No gut, hemal system (blood), nephridia or neurons
Epidermis for moving + nutrient uptake (simple)

35
Q

Why is difficult to classify phylums

A

Hard to see how the groups are related to one another

36
Q

What is characteristic that is strictly deuterstome

A

Gill slits

37
Q

What is ther difference btw radial and spiral cleavage

A

Radial - parallel / right angle to polar axis

Spiral - oblique to polar axis

38
Q

Why was the ancestral trait likely radial cleavage?

A

Only one major switch to spiral in platyhelminthes and mollusks and annelids

39
Q

What schizocoely?

A

Mesenchymal cells proliferate into balls of cells

They split to form mesodermally lined coelom

40
Q

What is enterocoely?

A

Outpockets from archentron (primary gut formed in gastrolation and then makes the mesoderm and the endoderm) close off and make enclosed mesodermally derived coelom

41
Q

How is the fate of cells following the earliest cleavage different in proto than deuter

A

Proto - determinate

Deuter - indeterminate

42
Q

How is the cleavage pattern different in proto than deuter

A

Proto - spiral

Deuter - radial

43
Q

How is the fate of the blastopore different in proto than deuter?

A

Proto - mouth first

Deuter - anus first

44
Q

How is the formation of the coelom different in proto than deuter?

A

Proto - splitting if mesoderm (schizocoely)

Deuter - out-pocketing of mesoderm (enterocoely)

45
Q

Chaetognatha are important for the food web because ….

A

Predators of zooplankton

46
Q

What do chaetognatha look like

A

Slender, shaft bodies, horizontal fins

47
Q

What do cheatognatha have for hunting on the sides of their head

A

Hooked chitinous grasping spines

48
Q

Why were chaetognatha previously thought of as deuterstomes?

A 
Radial cleavage
Blastopore
Coelom formation 
Tripartite body
Excretory
Circulatory
Cicular muscles
49
Q

What has a nervous system w cerebral ganglia + small eyes for light detection?

A

Chaetognatha

50
Q

What kind of development do chaetognatha have?

A

Direct

51
Q

Chaetognatha were thought to be related to deuterstomes… are they?

A

Currently with protostomes

52
Q

Why are chaetognatha so important to understand?

A

Evolution of morphological characters

Reconstruction of last common ancestor

Early develolmeng resembles radial cleavage

Invertebrate Biology (7 decks)

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