Quiz 1 - Phylogeny + Placozoans

Question 1

what makes a vertebrate a vertebrate

Answer 1

cranium

phylum chordata

Question 2

what are the benefits of the worm like body plan

Answer 2

efficient digestion

Question 3

what is disparity

Answer 3

morphological differences between major groups

Question 4

what is diversity

Answer 4

number of species

Question 5

why would one phylum be more diverse or disparate than another?

Answer 5

disparate phylum means more morphological changes between the phyls, less physical similarites

more diverse phyla means a higher number of species in this phyla than another - could be due to a basal split or an evolutionary change that only occurred in that phyla

Question 6

what was Darwin’s Dilemma

Answer 6

the seemingly rapid radiation of animals in the cambrian as this does not fit with the gradual change of evolution
- no fossil record evidence for this gradual change in the Cambrian

Question 7

why is hard to find pre-cambrian fossils

Answer 7

likely soft bodied animals, difficult to fossilize

Question 8

what is the oldest known fossils

Answer 8

bacteria - 3.5 bya

found in Australia

Question 9

what were found 3.4 bya found in shallow water ecosystems, microbial like mixed in with sediment that made a layer of organisms in the sediment record?

Answer 9

stromatolites - 3.4 bya

Question 10

What was the proteinaceous micro fossils that are said to emerge 3 bya that resemble pollen

Answer 10

acritarchs

Question 11

what are ichnofossils?

Answer 11

trace fossils

- preserved in sedimentary rocks that record biological activity

Question 12

has any trace fossil ever been accepted?

Answer 12

yes, trace fossil dating back to 560 mya were accepted

Question 13

when did the ediacaran begin? when did it end? when did the biota flourish

Answer 13

spanned from 635-543 mya

biota floursihed in 575 mya

Question 14

what is the poster fossil for ediacaran? it was found about 565 mya

Answer 14

rangeomorphs

Question 15

what do rangeomorphs look similar too

Answer 15

sea pens, but with fractal repitition

Question 16

what was the first pre-cambrian fossil to ever be named?

Answer 16

Charnia

- benthic, anchored to sea floor, lived in deep water, didn’t photosynthesize, no feed apparatus

Question 17

What is the oldest triploblastic bilaterian fossil discovered 555 mya

Answer 17

Kimberella

Question 18

what is the kimberella fossil a stem group of

Answer 18

molluscs

- it has radula marks which is a synaptomorphy of modern molluscs

Question 19

what is the difference between a stem and crown group

Answer 19

crown = last common ancestor of all living + extinct fossils (monophyletic)

stem = series of entirely extinct organisms that lead up to the crown group (paraphyletic)

Question 20

what is phylogeny

Answer 20

map of evol relationships btw organisms\
evol relatedness, similarities and differences of common ancestor

phyylogeny is inferred - changing all the time

Question 21

what is evolution

Answer 21

based on common ancestry + shared derived characters - change in heritable characters over millions of years

Question 22

what is taxonomy

Answer 22

classification system of organism based on common ancestors

arrangement of organisms based on descent

Question 23

what is cladistics?

Answer 23

based on shared characters that can trace them back to a common ancestor

Question 24

what helps placozoans stick

Answer 24

gland cells on ventral side

Question 25

what are placozoans covered in

Answer 25

dorsal and ventral ciliated cells

Question 26

what did metazoans evolve from 1.4 bya?

Answer 26

some flagellated cells

Question 27

do placozoans have sexual/embryonic cells?

Answer 27

nope, they have 4-5 somatic cell types

Question 28

the incisal cells in placozoans are missing what…

Answer 28

nuclei

Question 29

what is the rarest type of cell found in placozoans

Answer 29

crystal cells

• along perimeter of placozoan
• little, cup like cells wuth inorganic crystal inside

Question 30

what cell type was thought to be the pre-cursor to statocyst cells that help with orientation in placozoans

Answer 30

crystal cells

Question 31

how do placozoans eat?

Answer 31

phagocytosis / external digestion on ventral side

Question 32

where are placozoans found

Answer 32

mostly tropical and subtropics

Question 33

what are some derived features of placozoans with metazoans

Answer 33

loss of ribosomal protein genes

mtDNA showed mitochondral features only seen in poriferans + cnidarians

Question 34

what are some shared features of placozoans with fungi and choanoflagellates?

Answer 34

intrgenic spacers (introns)
large mtDNA

Question 35

placozoan have some genes that are similar to metazoans… what are they

Answer 35

Pax Genes - not found in placozoans but some variant of Pax gene found

Hox Genes

Question 36

how does the term GENES B4 PHENES apply to placozoans

Answer 36

they have the genetic makeup to build new metazoans, but just had yet to be expressed

Pax gene variant + Hox gene (sort of…)

Question 37

Pax genes are found in poriferna sand cnidairnas but not in placozoans… but they did find what in placozoans?

Answer 37

TripPaxB - an early version of the Pax gene from the same gene family

expressed differently in placozoans

Question 38

what are pax genes

Answer 38

control developmental genes that encode nuclear transcription factors - help make the nervous and sensory organs/systems

*mechanosensory systems

Question 39

hox genes are a type of…. what genes

Answer 39

homeobox genes

- involved in regualtion of development

Question 40

what is the hox gene function

Answer 40

patterning of the body

symmetry (something placozoans lack)

Question 41

do placozoans have hox genes

Answer 41

not really… they found homeobox genes in placozoans but their expressed differently

Question 42

explain the conclusions of the dellaporta 2006 paper on placozoan phylogeny i nthe metazoan tree

Answer 42

placos more basal than sponges based on mtDNA bc of shared features w choanflagellates + fungi

Question 43

why were sponges always thought to be the most basal

Answer 43

because of the choanoflagellate / chanocyte connection and the filter feeding

Question 44

how many homeobox genes have been identified in trichoplax adhereans

Answer 44

6 homeoboc genes

Question 45

explain Butschli placula hypothesis

Answer 45

flagellated protozoans formed a benthi-vagile, plate-like metazoan = placozoan

developped a 2 layered placula that had an upper ectoderm + lower endoderm

invagination of endodermal layer led to benthic animal

Question 46

the second mystery of placozoans is about their diversity… are they just one species? explain why or why not

Answer 46

diverse halophytes in subtropic oceans - each clade has its own niche based on its genetics… placozoans could be more diverse than originally thought

Question 47

it used to be thought there was only 1 species of placozoans… how many are known now

Answer 47

3 species

Question 48

what is the third mystery of placozoan

Answer 48

life cycles and reproduction

mostly reproduce asexually (binary fission or budding) but never seen them sexually reproduce

Question 49

what is convergent evolution

Answer 49

not monophyletic related, but evolved similar traits from have to adapt to similar environments/similar functions