Topic 18- Evolution of Jaws, Fish, and the Origins of Tetrapod Traits Flashcards
Gnathostomes are ___ vertebrates with __ pairs(s) of fins
They have ___ brains than in jawless vertebrates
further _____ of hox genes adds ____ diversity
- jawed,2
- bigger
- duplication, genetic
Are all hox gene duplications beneficial?
No, they create POTENTIAL for diversity of morphologies
where did jaws evolve from?
- modifications of 2 pairs of skeletal rods that has supported anterior pharyngeal slits
with hinged jaws, there were more ways of getting food than suspension feeding (using ___). What are the benefits of hinged jaws?
- pharynx
- can grasp, kill, shred, crush large food items
what are posterior slits specialized for?
gas exchange (gill slits!)
The earliest gnathostomes in the fossil record is an extinct lineage of armored vertebrates called ____ (~450 million yrs ago)
Placoderms
Class Chondichthyes is made up of ____ fishes (eg. ___, rays, chimeras)
Their __skeleton is made up of ___ but they have ___(calcified) teeth
- cartilaginous, sharks
- endo, cartilage, bony
Is the carliaginous skeleton in Chondrichthyes a primitive character state?
No, fossils suggest it’s a derived condition: evolved from ancestors with bony skeletons
In the development of most vertebrates, the skeleton is first ___ and then becomes _____
ie. cartilage is replaced by ______ ____, exception: ___________
cartilaginous
ossified (bony)
- calcium phosphate
exception: disks between vertebrae
which developmental step do chondrichthyans skip?
the ossification of the skeleton
instead of a gas-filled swim bladder, they stay buoyant using __ in their ____
oil in their liver
What are disadvantages of having a gas-filled swim bladder?
as pressure changes (as animal swims up/down) the sac can be expanded or compressed too much –> can be disadvantageous
The scales of sharks are structurally _____ to vertebrate teeth
- shark teeth are continuously ____
homologous
- replaced
what is the function of nostrils in sharks (& most other fish)
only for smelling, not for gas exchange
how do sharks detect changes in electrical fields (which are generated by _______)
- generated by muscular movement of other animals
- via the pores around their head
how do sharks detect vibrations in water?
via their lateral line (which is present in bony fish too)
shark sperm transfer through ____.
Fertilization is internal/external
eggs are protected in a ____
copulation (sex)
internal
leathery egg case
Lungs evolved in ____
fish
- evolved in water (aquatic environment) as a pre-adaptation to terrestrial life
extant bony fish descended from fresh of brackish (no O2) water ancestors who had :
1.
2.
- simple lung = ventral out-pocketing of foregut with gas
2. augmented gas exchange by gills
the original lung modified into a ___ ___ in most extant bony fish
swim bladder
What evolved from gills?
Gills –> ___–> ______
Gills–> Lungs –> swim bladder
Lungs and swim bladders are homologous/ analogous
homologous
they have the same evolutionary background
What are the functions of lungs vs swim bladders?
Lungs (paired): respiration Swim bladder (single): provide buoyancy
Lungs developed from a ___ out pocketing of the gut
Swim bladders developed from a ___ out pocketing of the gut
ventral for lungs
dorsal for swim bladders
The endoskeleton of bony fish is ____
ossified (bony)
In bony fish, the gill opening are covered by a single protective flap, the ____ which ____
operculum: it ventilates its gills
The scales of bony fish are ___ and ___-like rather than the tooth-like scales of chondrichthyans
flat
plate-like
Bony fish have ___ fins, unlike chondrichthyans
- they are used for ____ and ___
flexible
propulsion and maneuvering
Bony fish mainly use ___(internal/ external) fertilization
- Are the fertilized eggs cared for by the parent?
internal
- not usually, but sometimes (eg the seahorse)
Ray-finned fish are class \_\_\_ of bony fish - this class includes all \_\_\_\_ important fish
Actinopterygii
commercially
Class Sarcopterygii (___-finned fishes) have fleshy, paired fins which are joined to the body by _____
lobe-finned
a single bone
What are the 3 lineages of lobe-finned fish?
- Actinistia
- Rhipidista (Dipnoi)
- Amphibia, Reptilia, Mammalia
Class Dipnoi includes ____ which use 2 modes of gas exchange (___ and ____). They have a ___pump!
lungfish
lungs and gills
buccal
T/F:
Lungfish and Tetrapods are sister taxa
true
