chordate diversity Flashcards
four defining features of chordata?
Notochord
Dorsal, hallow nerve cord-
Pharyngeal slits or clefts-
Muscular, post anal tail
Cephalochordata (Lancelets) feeding method
filter feed by a mucous net
The 2R Hypothesis
genome duplication events between 564 and 450 MYA
(cephalochordata & tunicates have a single gene while vertebrates have 2 or 4 equivalent)
Myxini (hagfish)
Agnathans- “without jaw”
Feed by knotting and using teeth-like processes on tongue
Cartilaginous skeleton
Well developed notochord
Petromyzontida (Lampreys)
Agnathans – “without jaws”.
Larvae filter feeders, adults parasitic or do not feed. Notochord and simple vertebral column.
how many jawed fish clades are there
4
Chondrichthyes
Placoderms
Acanthodians
Osteichthyes
characteristics of Chondrichthyes
cartilaginous skeleton
well developed jaw
no swim bladder
lateral line system
fertilisation in Chondrichthyes?
all internal fertilisation
Actinopterygii (Fin fish)
Ossified endoskeleton (e.g. bones)
Skin covered in scales and mucus
Swim bladder
teleosts
Fins supported by rays
Jaw modifications
fertilisation in Actinopterygii
most have external fertilisation
Actinistia (Coelacanths)
fleshy fins
hinged skull
oviparous
2 living species
Dipnoi (lungfish) closest living relative to?
tetrapods
Osteichthyes
jawed with mineralise skeletons
origin of tetrapods
Date from late Devonian (375 MYA)
Limbs evolved from the fins of lobe-finned fish
Characteristics of amphibians
Thin skin with limited keratinisation
Skin permeable to oxygen and water
Most restricted to damp environments
the amniotic egg
4 specialised membranes
protect from desiccation,
allow gas exchange,
store food and waste
origins of amniotes
Carboniferous period
two main clades of amniotes
reptilia and mammalia
Testudines (turtles)
Terrestrial, freshwater and marine
Shells and skeleton are unique to clade
ancient reptilian characters in turtles
Skull morphology.
Scales (b-keratin).
Internal fertilisation but lay eggs
Ectothermic.
crocodilia (crocodiles and alligators)
All semi-aquatic predators ;most tropical
Have changed little since the Triassic.
Secondary palate.
Heart with septum, like birds.
characteristics of aves (birds)
Feathers (b-keratin).
Large, keeled sternum.
Fore-limbs modified for flight.
Hind-limbs for bipedal walking.
Internal fertilisation and hard-shelled amniotic eggs.
Endothermic.
sphenodontia (Tuatara)
One species of lizard-like
Carnivorous reptile found on islands off the coast of New Zealand
Squamata (snakes and lizards)
Mainly tropical, terrestrial carnivores
specialisation in snakes
limbless
elongated
modified jaw and skull
characteristics of mammals
Hair (a-keratin).
Specialised teeth (heterodont).
Articulation of jaw between dentary and squamosal bones.
Endothermic.
Internal fertilisation.
Amniotic eggs.
* Mammary glands.
