The New Phylogeny

Question 1

What are synapomorphies?

Answer 1

Shared, derived characters.

Question 2

When do changes that distinguish animals occur?

Answer 2

Embryonic development

Question 3

How did traditional morphological phylogeny divide the Metazoa

Answer 3

1. By protostomy and deuterostomy
2. Into coelomates and acoelomates
3. Articulata hypothesis.

Question 4

What does protostomy and deuterostomy refer to?

Answer 4

It refers to what the initial hole formed during gastrulation gives rise to. Protostomes the mouth forms first. In deuterostomes the anus forms first.

Question 5

What are diploblasts?

Answer 5

Only have an endoderm and ectoderm

Question 6

What is the role of the ectoderm?

Answer 6

Senses the environment

Question 7

What is the role of the endoderm?

Answer 7

Feeding

Question 8

What is the mesoglea?

Answer 8

The space between the endoderm and ectoderm

Question 9

What are triploblasts?

Answer 9

When the blastocoel fills with new tissue called the mesoderm

Question 10

What is a coelom?

Answer 10

Fluid filled cavity surrounded by mesoderm

Question 11

What are pseudocoelomates?

Answer 11

Where a mesoderm forms in the hole but incomplete. Not as well organised as a true coelomate

Question 12

What is the other name for pseudocoelomates?

Answer 12

Hemicoels

Question 13

What is a true coelomate?

Answer 13

Mesoderm completely lines the cavity

Question 14

Give an example of where molecular phylogeny has been used to find out stuff

Answer 14

Arrows worms (chaetognaths) unclear position - sequenced NAD5 found more similar to protostomes than deuterostomes, so placed there

Question 15

Why are molecules better than morphologies?

Answer 15

All morphology is under selection pressure and subject to convergent evolution. Molecules can change without affecting morphology

Question 16

What are expressed sequence tags (EST)?

Answer 16

Short sub-sequence of a cDNA sequence

Question 17

What is neutral theory?

Answer 17

A lot of DNA change is neutral, doesn’t affect the animal and occurs at a constant rate.

Question 18

What is the problem with molecular phylogeny?

Answer 18

Different types of DNA evolve at different rates, different for different animals. Some lineages evolve very fast, for example, maybe change in DNA repair mechanisms leading to many mutations very quickly, giving false differences between very similarly related animals. Long Branch Attraction is when these animals are grouped together because they’ve both undergone a lot of change, but artificial.

Question 19

How can the problems with molecular phylogeny be overcome?

Answer 19

Use slower evolving species, use out groups close to the animals in study, sample more species.

Question 20

What is amphistomy?

Answer 20

When the mouth and anus form at the same time

Question 21

What is the ancestral state of metazoa likely to be?

Answer 21

Deuterostome

Question 22

What does it mean for the protostomy that the metazoa is deuterostome?

Answer 22

It is not a synapomorphy

Question 23

What is protostomy more likely to be?

Answer 23

An apomorphy

Question 24

What is an apomorphy?

Answer 24

A novel evolutionary trait that is unique to a particular species and all its descendants

Question 25

What is deuterostomy likely to be?

Answer 25

A symplesiomorphy

Question 26

What is a symplesiomorphy?

Answer 26

An ancestral state shared between two or more taxa

Question 27

Where was priapulida traditionally placed, where is it placed now? How did that conclusion come to

Answer 27

Used to be protostome but if you look at the genes around where the hole is forming and later look at the genes around the anus you'll see they're the same. Same for genes expressed away from the blastopore. Now within deuterostomes

Question 28

Where are arthropods put now?

Answer 28

With ecdysozoans because of moulting

Question 29

Where are annelids put now?

Answer 29

With lophotrophozoans

Question 30

What is the movement of platyhelminths in the phylogeny tree?

Answer 30

Acoels were separated from nemertodermatida. Put at base. Looked at an acoel called xenoturbella, grouped within deuterostomes (v simple amongst complex, secondarily simplified? complexity indepdently evolved?). xenoturbella 2016: four new species found, moved back to basal bilateral group. Suggesting complexity increases over time.