Bilaterians Flashcards
Where did trace fossils first come from?
Animals going 3D- mixing sediments- burrowing- swimming- chasing
When did transition from 2D ‘biomat world’ to 3D world occur?
Cambrian start
3 clades of bilateria?
Lophotrocozoa, Ecdysozoa, Deuterostoma
What phyla included in Deuterostomia?
Echonoderms, Hemichordates and Chordates
What do deuterstomia have in common?
Deuterostomy and radial cleavage (these arent unique character)
What are the 5 classes of Echinoderms?
Asteroids (starfish); ophiuroids (brittle stars); Echinoids (sea urchins); holothurians (sea cucumbers); crinoids (sealilies + feather stars)
What is pentaradial symmetry?
5 fold
4 important features of Echinoderms
pentaradial symmetry, water vascular system, endoskeleton, marine
What symmetry do starfish and brittlestars have?
Bilateral- conserved from bilaterian ancestor?
How do starfish feed?
Gut extends down arms. Part of stomach extruded inside out into shell of prey, digestive juices released, can eat!
What is a use of the water-vascular system in Echinoderms?
Locomotion
Feature of Ophiuroids (brittle star)?
Thinner and bendier = for detritus feeding + NO ANUS
What is between Echinoids ossicle pines (which are covered in living tissue)?
Pedicellaria- chop up larvae that land- like little teeth
What do Holothurians (sea cucumber) do when attacked?
Eject Cuvierian tubules. If that doesn’t work.. .. then eject intestine!
What are the 2 classes of Hemichordates?
Enteropneusts (acorn worms) and Pterobranchs
How do Enteropneusts (acorn worms from Hemichordata) feed?
Pharyngeal slits- holes on side of body and cilia to make water current
+ filter feeds
Name 6 features of a generalised chordate
Pharyngeal slits; endostyle; dorsal hollow nerve chord; postanal tail; notochord; lateral muscles
Function of Pharyngeal slits in chordates?
Feeding and gas exchange
Function of endostyle in chordates?
Internal secretory structure of mucus - goes over pharyngeal slits
what germ layer is doral hollow nerve chord derived from in chordates?
ectoderm cells
Function of notochord in chordates?
Important for locomotion = skeletal structure down center of animal
What are the 3 subphyla of the phylum chordata?
Tunicates (urochordates); cephalochordates (amphioxus); vertebrates
What are the 3 groups within Tunicates?
Ascidiacaea (sea squirts); Larvacea; Thalacea
What does sessile mean?
Immobile
What is name for thick cellulose coat found on Ascidians?
Tunic
Where did genes for tunic of Ascidians (sea squirts) come from?
Horizontal gene transfer (from bacteria)
What do larvacea look like?
Sexually mature tadpoles in jelly houses
What do Thaliacea look like?
Sea quirts- but they can SWIM
What are 2 major changes in amphioxus (cephalochordata) body plans?
Notochord extends past brain for stiff tip for burrowing.
Pharyngeal slits no longer interact with outside world as water goes in atrial cavity and out atrial pore
What are the 3 clades of bilaterina?
Lophotrochozoa, ecysozoa and deutrostomia
What phyla are included in Ecdysozoa?
2x wormy; nematodes and nematomorphs
3x leggy; tardigrades onychophora and arthropods
What do ecdysozoa have in common?
They moult (ecdysis)
Name 2 characters of nematode worms
Stiff (non-stretchy cuticle) and NO segmentation
How do nematode worms move?
Stiff but bendy cuticle and antagonistic longitudinal muscles = SINOUS BODY WAVES
How to nematode worms solve problem of high pressure squeezing out gut contents?
Muscles - e.g. triradiate pharynx at mouth
How does nematode cuticle have spring effect?
Several layers of helical cortical fibres in different directions
Give an example of a nematode worm parasite with a 2 host life cycle
Onchocerca volvulus= river blindness
- humans and black flies
How do we exploit nematode worms?
Use as biological control e.g. slug killer
BUT this is introducing invasive species
What is the developmental model system nematode worm?
C. elegans
How are nematomorphs different to nematodes?
CRAZY LONG AND REDUCED GUT
How do nematopmorph larvae return to water once developing inside adult cricket?
MIND CONTROL- makes cricket wander eratically
What can tardigrades do when not in water?
anyhydrobiosis
What is anyhydrobiosis?
organism becomes dry and dormant until living conditions are favorable.
how were ECDYSOZOA discovered as a clade?
DNA sequencing
What is a key feature of annelids?
Segmentation
What clade do lophotrocozoa belong tp?
Bilateria
What does vermiform mean?
Worm-shaped
What is a hydrostatic skeleton?
big fluid filled spaces (water not very compressible) e.g. in annelids
Why are annelids always aquatic?
Have water permeable skin
What are the 3 classes of annelida?
polychaeta, oligochaeta and hurudinea
What are the 2 main types of polychaetes?
Errant (mobile) and sedentary
What are parapodia in polychaetes?
Triangles on sides, like oars for extra power
How do polychaetes reproduce?
dioecious- external fertilisation and larval stage
Differences between polychaetes?
1- freshwater
2- no parapodia
3- no eyes/ tentacles on head
40- hermaphrodite
What does the clitellum do in oligochaetes?
secretes mucus coccon to pick up eggs and sperm - then leaves all behind
How were leeches used in microsurgery?
used for anticoagulants and to remove blood
what 3 features of flat worms tell you they’re bilateria?
1- three germ layer
2- bilateral symmetry
3- centralised nervous system
What feature do flatworms lack that are seen in other bilateria?
no body cavity, no gills, no blood system, no anus
What is an eversible pharynx?
can go inside out e.g. flatworms
Where do polyclads exist?
MARINE
What is a neoblast?
adult stem cell
what is amazing about triclad (planarian) regeneration?
cut any part and whole body will regenerate
How do cestodes (parastic flatworms) grow?
from middle- pushing segments out
what is the second biggest phylum after arthropods?
mollusca
Name 2 major body plan features of molluscs?
trough-gut and not-segmented
What are molluscs shells made of?
Mantle = extracellular caco3 + proteins
why do mollusc shells coil?
to increase volume as can only grow at edges
What are the 3 main classes of mollusca?
gastropoda, bivalvia, cephalopoda
What are 3 characteristic traits of gastropoda?
1- 1 shell
2- use radula
3- slow moving grazer
What is torsion in gastropods?
body twists 190 degrees anticlockwise during development
What is an interesting defence mechanism in nudibranchs?
Eat immature nematocysts from prey- out at tips of cerata and use to sting
What are 3 main characteristic traits of Bivalvia (mollusca)?
2 shells, foot in between, no radula
What is an example of a developed ccephalopod?
octopus, squid, cuttlefish
how do cephalopoda move?
gas in shell for up and down and water expulsion fro propulsion
do bivalvia have eyes?
not generally but some evolved constructive interference e.g. scallops
What are the 3 subphyla of chordates?
Urochordates, cephalochordates, vertebrates
What are the 2 main components of bone?
collagen fibres and calium PHOSPHATE crystals
What do osteoblasts do?
make bone
What do osteoclasts do?
break down bone
What do osteocytes do?
detect strain and cracks
What part of body plan, in somite, forms bone?
Sclerotome
What do neural crest cells form?
sensory nerves, pigment cells, nerves in gut and autonomic nervous system + in head forms more skeleton
