L1 - Vertebrate Origins Flashcards
What 2 categories do modern deutrostomes fall into?
- Echinoderms + Hemichordates
- Chordates - ancestors of these had non-feeding tadpole like larvae and a notochord
What are Echinoderms and Hemichordates characterised by?
characterised by a 3 part coelom, bilateral symmetry and ciliated larvae
What time period are the fossils of yunnanzoans fossil found in?
Cambrian
The phylum Hemichordates comprises of 4 classes, what are they?
1) Enteropneusta - acorn worms
2) Pterobranchia - sea angels
3) Planctosphaeroidia - known from larvae or single species
4) Graptolithina - extinct
What are the 3 body part Hemichordates are characterised by?
- Proboscis
- Collar
- Trunk
Where do all Enteropneusta live?
In mud or sand burrows
How do Enteropneusta feed?
Their proboscis is a digging and feeding organ, coated in mucus, which traps prey in the sediment.
Particles are trapped in the mucus and transported by cilia to the mouth where they are sorted by the pre-
How do each reproduce:
a) Enteropneusta
b) Pterobranchia
a) Sexual - mostly small yolky eggs, some species have large yolky eggs
b) both asexual and sexual
- asexual - can bud new zooids from adhesive disc
- sexual - colonies are hermaphroditic but individual zooids are usually male or female. Larvae develop in a particular part of the tube then settle and form a new colony elsewhere
Where do Pterobranchia live?
On hard substrates in Antarctica
What 5 features are chordates characterised by?
- ventral heart
- pharyngeal arches
- dorsal hollow nerve chord and supporting notochord
- a groove in the ventral wall of the pharynx - Endostyle
- tail that extends beyond the anus
What 3 subphyla are in Chordata?
- Urochordata
- Chephalochordata
- Vertebrata
Where do each live?
a) Urochordata
b) Chephalochordata
a) Urochordata - all are marine, and are mainly sessile as adults
b) Chephalochordata - buried in soft marine sediments
Within verbrata there are 2 classes, what are they?
- Agnatha
- Placodermi
What 2 fish types are the only remaining Agnatha after the Devonian period?
Hagfish and Lampreys
What kid of fish did Agnatha give rise to?
They are filter feeders and gave rise to jawless fish
