Lecture 7: Amniotes Flashcards
Which of the following do placoderms and ostracoderms have in common?
a) Both have jaws
b) Bony head shields
c) Pelvic fins
d) None of the above
a) Bony head shields
What is vertebrate terrestrialization?
the evolution of fish to tetrapods
When did tetrapods diverge from lobe-finned fish (Scarcopterygians)?
Devonian period or earlier - 375 to 385 MYA
When did adaptations to terrestrial life for tetrapods occur?
earliest Carboniferous period - 345 - 359 MYA
What advantages did tetrapods have in shallow aquatic areas?
a) ability to use limbs to walk on ground/water - the extension of their digits on their feet
b) required less energy for swimming
c) Shallow water presence meant fewer predators on tetrapod young
d) significant changes in the atmosphere
- lower sea levels
- increased oxygen levels
Which class of vertebrates do not have a swim or gas bladder?
Chondrichthyes (Sharks, Rays & Skates)
- they don’t have lungs
- use their gills and tail to maintain buoyancy in water
Which superclass of vertebrates have a swim or gas bladder (the first ones that we see having them)
Osteicthyes (“bony fish”)
- Ray-finned fish
- Salmon
What is a gas bladder and swim bladder? what is the difference b/t a swim bladder, gas bladder, respiratory gas bladder?
A gas bladder is an elongated gas-filled sac, and the changes within that gas bladder will dictate where the fish sits in the water. A swim bladder is when air comes in and is used predominantly to control buoyancy.
Generally, if the organ functions predominantly in breathing, it is considered a lung or a respiratory gas bladder.
What is Dual pumping?
& in which fish do we see this style of breathing in?
There are 2 phases:
> Mouth is open, opercula is closed, buccal cavity expands and opercula expands
> Mouth is closed, opercula is open, buccal cavity contracts, opercula cavity contracts
We see dual pumping in more primitive fish such as the Chondrichthyes (cartilaginous fish)
What are the three differences b/t the swim bladders and the lung bladders?
- The swim bladder is dorsal to the digestive tract, and the lungs sit ventrally
- Swim bladders are usually single (lungs = paired)
- Direction of circulation
What is one vertebrate where we see only one lung rather than a pair of lungs?
Snakes!
What is Buccal Pump breathing, and how does it work?
-Similar to dual pump breathing, but with less focus on operculum
-focus is on mouth/buccal cavity
-Mouth open, buccal cavity expands (brings water/air in)
-Mouth closed, opercula open, buccal cavity contracts, opercula cavity contracts (pushes air/water further down)
-Less use of gills
- Seen in Actinopterygii
What is breathing, and how does it work?
- Tipping up and gulping for air likely evolved for lungs
- Pair of lungs (left and right)
- Air-breathing therefore not a feature for tetrapods adapting to life on land
- Seen in lungfish
What prompted fish to develop air-breathing?
low oxygen levels in the ocean
When did lungs start to develop?
Evolved 430 MYA
- This happened 50 MY before movement onto land
What are the three main orders of the early tetrapods? (transition to amniotes)
- Icthyostega
- Temnospondyls –> modern amphibians
- Anthracosaurs
When did early tetrapods start to transition to amniotes?
a) Early Paleozoic era
b) Late Paleozoic era
c) Early Mesozoic era
d) Mid Paleozoic era
e) Carboniferous period
b) Late Paleozoic era and this was when Pangea was formed, the connection to the water was strong
What Superclass and class & subclass does icthyostega belong to?
What features do icthyostega have?
Superclass: Ganothostomata = Jawed vertebrates
Class: Amphibia
Subclass Labyrinthodontia
*Notochord is extended into the braincase
*Dorsalventral flexion of the vertebral column (distinct for tetrapod) - they can move their head up and down
>Function unknown
*Internal gills
*Limbs with digits
*Polydactyl feet (7)
What Superclass and class & subclass does Temnospondyl belong to?
What features does Temnospondyl have?
Superclass: Ganothostomata = Jawed vertebrates
Class: Amphibia
Subclass Labyrinthodontia
Order: Temnospondyl
- led to amphibians
- Emerged 330 MYA (Paleozoic Era = survived)
- had flat skulls
- robust, sturdy limbs
- More robust limbs and girdles - important feature compared to Icthyostega and Acanthostega
- unknown common ancestor (example: Eyrops)
*The temnospondyls were the most successful early tetrapodomorphs (intermediate between fish and tetrapods)
*Diversified about 100 MYA on land and in sea
*Some were as big as a car
(Metoposaurus)
*Relied heavily on water due to laying eggs
*At this time, the earth was carboniferous, and it was like a paradise to the amphibians
*The environment was changing (climate change), which threatened their egg survivability.
*The temnospondyls were still able to do well despite competition with other early vertebrates (crocodilians and amniotes)
What group emerged from temnospondyls?
Amniotes
During which period did the climate of Pangea start to change and become drier?
A) Devonian Period
B) Jurassic Period
C) Permian Period
D) Cretaceous Period
E) Carboniferous period
In the Paleozoic era in the Carboniferous period in the Pennsylvanian Epoch
What is the difference between Amniota and Anamniotes?
Amniota or amniotes are birds, mammals and reptiles, and they lay shelled eggs on land, whereas anamniotes lay eggs on water and they are fish and amphibians.
What types of eggs have their embryos developed in an extraembryonic membrane?
Amniotic eggs !
What types of eggs have a leathery/hard shell surrounding them?
Cleidoic eggs!
