animal evolution Flashcards
why are shared embryological characters important
for working out relationshisp
gastrulation
formation of gut during embryonic development
process of gastrulation
blastula invaginages to form inner and outer layers of ecoderm and endoderm, and in some cases, mesoderm
zygote to 8 cell stage to blastula to gastrula
blastula
hollow ball of cells that gastrulates to form the ectoderm and endoderm
achenteron
ancient gut cavity
radial celavage example
sea urchins strongylocentrotous purpuratus
spiral cleavage example
maritigrella crozier
cleavages in deuterostomes
radial
cleavages in protostomes
spiral
triploblasts properties
have 3 cell layers (endoderm, ecoderm, mesoderm)
have a through gut
seperate mouth and anus
bilateraially symmetrical (dorsal and ventral)
what does the mesoderm become
muscles blood bone and tissue
triploblasts examples
apes clowfnish slug
diploblasts properties
2 cell layers [endoderm and ecoderm]
blind gut; allows for food and wate to pass through same opening
gadially symmetrical (oral and aboral axis)
what does recent molecular data challenge about triploblasts and diploblasts
1) whether cnidarians only have two tissue layers
2) whether chindarisn are actually radial symmetrical
cnidarians and 2 tissue layer
stienmetz; gut like ectodermal tissue (pharygeal endoderm) present in sea anemon challenges germ layer homology
middle cell layer; maybe differentiate differently but present in both; challenges view that ectoerm is homolougous with animals
cnidarians and radial symmetry
genes show that bottom has different genes than in the top of cnidarians even though they LOOK radially symmetrical
radial symmetry
cleave during which the cleavage planes are either parallel or perpendicular to the vertical axes of the embryo
spiral cleavage
cleave in which the planes of cell deivision are diagonal to the certical axes of the embryoo
TRIPLOBLASTIC VARIATIONS
ACOELOMATE
PSEUDOCEOLOMATE
COELOMATE
acoelomate
meants without
an extoder, without solid mesoderm, endoderm
e.g. flatworms like platyhelminth
pseudocolomate
mesodemr has a cavity
e.g. nematode (fluid filled space)
coelomate
mesoderm has epitlial lined cavaity
e.g. vertebrates and annelids
ecdysis
moutling ot cuticle with growth like in scorpions or priapulid worms
segmentation
repeated units of construciton along anteroposterior axis like annelids
opisthokonts
‘rear facing flagellum’; animals such as fungi, choanoflagallets an dother
the closest clade to animals; include fungi and choanolglatallets
all have posterior flagellum
what to animals and opisthokonts share
an additional amino acid in elongation factor one alpha rpoteins resuting in sperm cell having a posterior flagellem
anterior flagellum
euglena
sponges
animals collage multicellular seperate junctions spermatozoa;
similar unicellular complexes like choanoflgallates such as choanocyte cells inw ater that filter feed by creating currents to suck water in
first sign of life
1 billion years ago
twitya formation
canada; 610 mya
ediacaran fossils
named after ediacara history of australia
sedimentary rocks that used to be uniceliar
vendian
what russians called the ediacarn fossils on the winter coast
origins of ediacaran fossils
carbonate layer appeared post-ice age
why do scientists think ediacarans are snimals
similar to animal fossils in youner proterozoic rocks
formed in deep water
not carbon preserved; impressions hence not made by plants
simplest metazoans living today are sea anomons, corals and jellyfish that resembl them
porifera and ediacara
similar structures to ediacaran sponges
all sponges have splerocytes which take in minerals from water for agility and strength
e.g. hexactinellida and paleophramodicta
cnidarians and ediacara
even more similar to modern fossils
e. g. dickinsonia
e. g. carnia
protostomes
ecydsozoa and lophotrophozoa
diploblasts
cetenophores cnidarians
what are ctenophora
sea goosebeeries or comb jellies
big creatures with ‘‘corn rows’ (compound cilia)
are predators; tenteacles or telophores catch fish
mroe complex than sponges
trichoplax adhaerans
placazoa phlyum; diploblasts
more simple than cnidarisn but closer realted ot us; more complex ancestors probabled symplified
tricho= hair plate
have 4 cells
reprdocue by sex for genetic mixture (no one has seen egg or sperm) AND binary fission
share features with metazoas (complex genetic pathways)
earliest evdiecne for triploblasts
more complex movement and activity
produce trace fossils
appear suddenly in fossil record
many different groups
lack of evidence of cambrian evidence before explosion?
minute animals
cryptic animals
arose quickl after instaed
triploblastic ediacaran fossils
spiriliginna (became arthopod)
tribachinidium (became echinoderm)
kimbella (became mollusc)
cambrian explosion
increase in oxygen levels
end of snowball earth and genetic bottle necks caused diversification
calcium from midearth ridges allowed for skeletons of calbium carbondate to be made
genetic and developmental invetion such as hox genes
predator prey arms race
hox genes…?
patern anteror posterior axis developments
who discovered the burgess shale
charles doolittle walcrot; his horse opened a rock with a fossil
cambrian fossils examples
lopopod
marelia
sanctacrans
pikalia
wiwaxia
opabina
hallucidengia
opabina
has a long flexible probisics with grasping spines; resulted in laughter when presented in converence
lophotrophozoa
flatworms
molluscs
annelids
lophphorates
ecdysozoa
nematods and arthopods
deuterstome properties
radial and intermediate cleavage
enterocoleous formation of colelom (folds of archeteron from coleom)
anus develops from blastorpore
mouth derives from second opening in embryo
protostome properties
spiral and determine cleavage
schizocoleous coelom formation (soilid masses of mesoderm split to form colelom)
mouth develops from blastopore
mouth derives form first opening
parazoa
sponges; no tissues
radiata
cnidarians and ctenophorans; radial symmetry
lophotrocohoza
grow by increasing body mass, locomotion and trochophore larvae
tree of life…
not ladder of life (hierarchy is bad and there is not top of evolutionary tree)
its not a progression; common ancestors are basel
basal and primitive
- refer to primitive common ancestors, not current species as direction of evolution is derived from ancestry
hence fossils basal to living groups
homologoy summary
common traits due to common descent such as legs
animals with legs are parismonions and closly related
homology of genes easier to determine (e.g. hox4 mous and drosphpila gene)
ancestral homolougs characters as synamophories hence informative and determine ingroups
analogy summary
convergent evolution
dorsal fin of sharks and dolphins for example indepent (fish and mammals are different species)
mithoncdrial gene order and synanomorphy
crustceans and insects have similar red gene
centipedes and spiders have this red gene seomewhere else
homoplasy
similarity due to convergent evolution ; placing analogous species together on assumption they are homologous
example of homoplasy
tansmian wolf (now extinct) and wolf where placed together due to hunter, jaws, and skulls but in reality wolf more closely related to kangaroo and tasmainan wolf is a marsupial more closely related to human
character loss and phylgentic confusion
converges happens or characters are lost than can cause confusion
whale and shark
whales more related to cows but whales have retired to sea; thought to be related to sharks; not true
urochordates (seasquirts) and molluscs
sea squirts are actually more closely related to fish but lose traits to become sessile filter feeders
hierarchy misconception of animal evolution
diploblasts to acoelomates to pseudomates to coelomates
truth about hierarchy misconception of animal evolution
- colemic body and cleaveals is randomly dispered
