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2nd Year: Animal Biodiversity > Introduction to phylogenetics, the protostomes and the deuterostomes > Flashcards

Introduction to phylogenetics, the protostomes and the deuterostomes Flashcards

1
Q

Define a clade.

A

A monophyletic group, including a common ancestor and all its descendants.

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2
Q

Define a paraphyletic group.

A

A common ancestor and some of its descendants.

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3
Q

Define a metazoan.

A

A multicellular eukaryote, an ‘animal’.

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4
Q

When do the metazoans originate from?

A

The Cambrian Explosion.

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5
Q

When was the Cambrian explosion?

A

540mya

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6
Q

Define a heterotroph.

A

An organism that derives its nutrients from complex organic sources.

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7
Q

Approximately how many metazoan phyla are there?

A

~30-40

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8
Q

How many species of metazoan are there?

A

~1.3million.

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9
Q

What proportion of metazoans are insects?

A

2/3

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10
Q

What percentage of all metazoans are coleoptera (beetles)?

A

1/4.

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11
Q

Approximately how many species of mammal are there?

A

4000

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12
Q

What kind of data is the new animal phylogeny based on?

A

Molecular

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13
Q

What kind of data were old style cladograms based on?

A

Morphological data from the fossil record and living specimens.

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14
Q

What are 2 benefits of using morphological data?

A
  1. Helps us to group animals for which we cannot get any DNA
  2. Helps us to determine ancestral states
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15
Q

Morphological and molecular data are now used in combination with each other. True or false?

A

True.

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16
Q

What are the 2 categories of metazoan?

A
  1. Bilateria

2. Non-bilateria

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17
Q

Define a bilaterian.

A

An organism with bilateral symmetry and 3 germ layers.

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18
Q

Define cephalisation.

A

The concentration of sensory organs and nervous control at the anterior of the animal.

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19
Q

What are the most basal metazoans?

A

Ctenophores (comb jellies)

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20
Q

It is thought that ctenophores evolved muscles and neurons by parallel evolution to the rest of metazoa. What does this mean?

A

Where the same trait evolves in distinct but related groups that descend from the same ancestor.

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21
Q

The bilaterians are split into the protostomes and deuterostomes. What 2 groups make up the protostomes?

A
  1. Lophotrochozoa

2. Ecdysozoa

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22
Q

Which forms first in protostomes, the mouth or the anus?

A

The mouth forms first from the blastopore.

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23
Q

What kind of cleavage do protostomes have?

A

Spiral cleavage

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24
Q

In protostomes, the mesoderm is formed by…?

A

Schizocoely.

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25
Q

The bilaterians are split into the protostomes and deuterostomes. What 2 groups make up the deuterostomes?

A
  1. Ambulacraria

2. Chordata

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26
Q

What groups make up the ambulacraria?

A

The echinoderms and hemichordates.

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27
Q

The larvae of echinoderms have bilateral symmetry. What kind of symmetry do the adults have?

A

Pentaradial

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28
Q

What are the skeletons of echinoderms made from?

A

Their skeletons are calcitic and made from CaCO3 (calcium carbonate)

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29
Q

What is ‘stereom mesh’?

A

The structure of echinoderm skeletons.

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30
Q

Pharangial slits (gill slits) are typical of all chordates. True or false?

A

True.

31
Q

Which gene controls the formation of pharangial slits?

A

Patch19

32
Q

Where is patch19 expressed?

A

In the developing gills of chordates and during the gill patterning of hemichordates.

33
Q

Which 3 groups make up the chordates?

A
  1. Cephalochordata
  2. Urochordata
  3. Vertebrata
34
Q

In the deuterostomes which forms first, the mouth or anus?

A

The anus forms from the blastopore.

35
Q

What kind of cleavage do deuterostomes undergo?

A

Radial.

36
Q

In deuterostomes the mesoderm is formed by…?

A

Enterocoely.

37
Q

Deuterostomes have trimery. What does this mean?

A

3 fluid-filled coeloms.

38
Q

The echinoderms are the most primitive bilaterian clade. Which was the next to evolve?

A

The hemichordates.

39
Q

Which was the last of the 3 major bilaterian clades to evolve?

A

Chordata.

40
Q

The echinoderms and hemichordates are largely motile. True or false?

A

False - they are mostly sessile (sedentary).

41
Q

How many taxa of echinoderms are there?

A

5

42
Q

How many taxa of hemichordates are there?

A

2

43
Q

Most chordates have a notochord to protect their dorsal hollow nerve chord. What are the vertebrate equivalents of these?

A

A backbone protecting the spinal cord.

44
Q

Within the chordates, which group is more closely related to the vertebrates?

A

The urochordates.

45
Q

Why was it previously thought that vertebrates were more closely related to the cephalochordates? What does this say about urochordates?

A

They both have fish-like larval stages. Urochordates may also have had a fish-like larval stage that has been lost in regressive evolution.

46
Q

Urochordates display multiple instances of regressive evolution. Give an example.

A

They have lost some HOX genes.

47
Q

What is characteristic about the dorsal-ventral axis in both invertebrates and vertebrates?

A

Invertebrates have their hollow nerve cord/notochords on the ventral side, whereas it is on the dorsal side of vertebrates.

48
Q

The xenoturbella and acoelomorpha were both misclassified as what group?

A

Platyhelminthes, which are protostomes.

49
Q

Xenoturbella and acoelomorpha underwent DNA analysis and were then classified as molluscs. Why was this wrong?

A

The mollusc DNA came from their stomach contents.

50
Q

Now, after mtDNA anaylsis, what are xenoturbella and acoelomorpha both thought to be? Why is this controversial?

A

Deuterostomes, but xenoturbella is missing the patch19 gene that determines the pharangial slits in chordates.

51
Q

Scientists are unsure where Chaetognaths should be placed as they have a) deuterostomic and b) protostomic qualities. What are they?

A

a) Radial cleavage and enterocoely

b) The NAD5 gene in mtDNA

52
Q

Lophophorates are now classified with the protostomes. Why was it previously thought they were deuterostomes?

A

They possess a lophophore feeding structure, similar to that in hemichordates which are deuterostomes.

53
Q

How was it confirmed that lophophorates are in fact protostomes?

A

The possess a NAD5 gene

54
Q

The pogonophores were thought to be deuterostomes because they display trimery. Why was this wrong?

A

Pogonophores actually have 20+ coelomic cavities, much like protostomic annelids, however most of these are hidden in the substrate.

55
Q

How must the binomial name of organisms be written?

A

In italics.

56
Q

How can you identify a word is indicative of a family?

A

It ends in -ae

57
Q

What is phylogenetics?

A

The sistergroup relations between taxa based on their genetics, i.e. how closely related they are

58
Q

When do phylogenetic trees date back to?

A

1837.

59
Q

Define cladistics.

A

The study of shared physical and morphological characters.

60
Q

What is sexual dichromatism?

A

A difference in colour/patterning between the sexes.

61
Q

In phylogenetics, what is the root of a tree?

A

The ancestor of all the organisms in that tree.

62
Q

In phylogenetics, what is an internal node of a tree?

A

Hypothetical ancestors, where 2 branches connect.

63
Q

In phylogenetics, what are the terminal nodes?

A

The most recent organism in the tree where a lineage ends.

64
Q

If a tree is fully resolved, what does this mean about the relationships?

A

There is complete certainty of the relationships.

65
Q

If a tree is partially resolved, what does this mean about the relationships?

A

There is some doubt.

66
Q

Define polytomy.

A

Where a node splits into more than 2 branches.

67
Q

There are 2 types of polytomy. What are they? Explain them.

A
  1. Hard: a simultaneous speciation event where there is complete certainty of relationships
  2. Soft: unsure of the relationships between organisms
68
Q

Define a synapomorphy.

A

A shared derived character, displayed by the ancestor and all its descendants.

69
Q

What is an ultrametric tree?

A

One where the time scale is indicated.

70
Q

Define a plesiomorphy.

A

An ancestral morphology that has been lost in some of the descendants.

71
Q

Define an autopomorphy.

A

A unique character state used for identification.

72
Q

Define a homoplasy.

A

Homologous characteristics resulting fom convergent evolution. ‘The same feature from a different ancestral morphology’.

73
Q

Why are homoplasies misleading?

A

They make it look like organisms are related when they aren’t.

2nd Year: Animal Biodiversity (16 decks)

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