Topic 18- Evolution of Jaws, Fish, and the Origins of Tetrapod Traits

Question 1

Gnathostomes are ___ vertebrates with __ pairs(s) of fins
They have ___ brains than in jawless vertebrates

further _____ of hox genes adds ____ diversity

Answer 1

• jawed,2
• bigger
• duplication, genetic

Question 2

Are all hox gene duplications beneficial?

Answer 2

No, they create POTENTIAL for diversity of morphologies

Question 3

where did jaws evolve from?

Answer 3

• modifications of 2 pairs of skeletal rods that has supported anterior pharyngeal slits

Question 4

with hinged jaws, there were more ways of getting food than suspension feeding (using ___). What are the benefits of hinged jaws?

Answer 4

• pharynx

- can grasp, kill, shred, crush large food items

Question 5

what are posterior slits specialized for?

Answer 5

gas exchange (gill slits!)

Question 6

The earliest gnathostomes in the fossil record is an extinct lineage of armored vertebrates called ____ (~450 million yrs ago)

Answer 6

Placoderms

Question 7

Class Chondichthyes is made up of ____ fishes (eg. ___, rays, chimeras)
Their __skeleton is made up of ___ but they have ___(calcified) teeth

Answer 7

• cartilaginous, sharks

- endo, cartilage, bony

Question 8

Is the carliaginous skeleton in Chondrichthyes a primitive character state?

Answer 8

No, fossils suggest it’s a derived condition: evolved from ancestors with bony skeletons

Question 9

In the development of most vertebrates, the skeleton is first ___ and then becomes _____
ie. cartilage is replaced by ______ ____, exception: ___________

Answer 9

cartilaginous
ossified (bony)

• calcium phosphate
  exception: disks between vertebrae

Question 10

which developmental step do chondrichthyans skip?

Answer 10

the ossification of the skeleton

Question 11

instead of a gas-filled swim bladder, they stay buoyant using __ in their ____

Answer 11

oil in their liver

Question 12

What are disadvantages of having a gas-filled swim bladder?

Answer 12

as pressure changes (as animal swims up/down) the sac can be expanded or compressed too much –> can be disadvantageous

Question 13

The scales of sharks are structurally _____ to vertebrate teeth
- shark teeth are continuously ____

Answer 13

homologous

- replaced

Question 14

what is the function of nostrils in sharks (& most other fish)

Answer 14

only for smelling, not for gas exchange

Question 15

how do sharks detect changes in electrical fields (which are generated by _______)

Answer 15

• generated by muscular movement of other animals

- via the pores around their head

Question 16

how do sharks detect vibrations in water?

Answer 16

via their lateral line (which is present in bony fish too)

Question 17

shark sperm transfer through ____.
Fertilization is internal/external
eggs are protected in a ____

Answer 17

copulation (sex)
internal
leathery egg case

Question 18

Lungs evolved in ____

Answer 18

fish

- evolved in water (aquatic environment) as a pre-adaptation to terrestrial life

Question 19

extant bony fish descended from fresh of brackish (no O2) water ancestors who had :
1.
2.

Answer 19

1. simple lung = ventral out-pocketing of foregut with gas

2. augmented gas exchange by gills

Question 20

the original lung modified into a ___ ___ in most extant bony fish

Answer 20

swim bladder

Question 21

What evolved from gills?

Gills –> ___–> ______

Answer 21

Gills–> Lungs –> swim bladder

Question 22

Lungs and swim bladders are homologous/ analogous

Answer 22

homologous

they have the same evolutionary background

Question 23

What are the functions of lungs vs swim bladders?

Answer 23

Lungs (paired): respiration 
Swim bladder (single): provide buoyancy

Question 24

Lungs developed from a ___ out pocketing of the gut

Swim bladders developed from a ___ out pocketing of the gut

Answer 24

ventral for lungs

dorsal for swim bladders

Question 25

The endoskeleton of bony fish is ____

Answer 25

ossified (bony)

Question 26

In bony fish, the gill opening are covered by a single protective flap, the ____ which ____

Answer 26

operculum: it ventilates its gills

Question 27

The scales of bony fish are ___ and ___-like rather than the tooth-like scales of chondrichthyans

Answer 27

flat

plate-like

Question 28

Bony fish have ___ fins, unlike chondrichthyans

- they are used for ____ and ___

Answer 28

flexible

propulsion and maneuvering

Question 29

Bony fish mainly use ___(internal/ external) fertilization

- Are the fertilized eggs cared for by the parent?

Answer 29

internal

- not usually, but sometimes (eg the seahorse)

Question 30

Ray-finned fish are class \_\_\_ of bony fish
- this class includes all \_\_\_\_ important fish

Answer 30

Actinopterygii

commercially

Question 31

Class Sarcopterygii (___-finned fishes) have fleshy, paired fins which are joined to the body by _____

Answer 31

lobe-finned

a single bone

Question 32

What are the 3 lineages of lobe-finned fish?

Answer 32

1. Actinistia
2. Rhipidista (Dipnoi)
3. Amphibia, Reptilia, Mammalia

Question 33

Class Dipnoi includes ____ which use 2 modes of gas exchange (___ and ____). They have a ___pump!

Answer 33

lungfish
lungs and gills
buccal

Question 34

T/F:

Lungfish and Tetrapods are sister taxa

Answer 34

true