Amphibians Flashcards
What set the stage for the invasion of land?
The evolution of lung-like sacs in response to the inadequacy of gills for respiration in oxygen poor waters
How could increasing temperatures lead to the development of lung-like sacs?
In hot conditions there is less oxygen in the water
Give an example of a lobe finned fish
Coelacanth
Give some features of lobe-finned fish:
Fleshy, lobed, paired fins that are joined to the body by a single bone
Pectoral and pelvic fins resemble tetrapod limbs
What do all sarcopterygians possess?
Teeth covered with enamel
What lineage of fish is thought to of given rise to tetrapods?
Sarcopterygii
Lobe finned fish
What fish is the closest extant relative to tetrapods?
The lungfish
What did the tetrapod legs evolve from?
The pectoral girdle and fins attached to opercular bones over the gills- which can be used to push along the terrestrial environment
What are the advantages of separating the pectoral girdle from the skull?
Greater mobility permitting greater feeding
Improved articulation of the jaw
Overall improves feeding
What are the advantages of fish moving to terrestrial life?
Gain access to insects and plants
Dispersal to improve genetic diversity
Escape from predatory fish
More niches available
What are the consequences of terrestrialisation?
Have to adapt senses
Need to change reproduction- can’t have external fertilisation
Change circulatory system
What are the skeletal adaptations of terrestrialisation?
Undulatory locomotion
Suspension of vertebral column
Regionalisation is vertebral column
Suspension of internal organs
Reorganisation of the skull
What evolved in between the vertebrae to provide support?
Zygapophyses
Now absent in modern aquatic mammals
What are the two tetrapod skeletons that tetrapods evolved from?
Acanthostega:Late Devonian, 8 toes on the forelimb
Icthyostega: Late Devonian, 7 toes on the hindlimb
What were the characteristics of early/non-amniote tetrapods?
Scaled
Conservative body plan- crocodile like
Most wiped out in the Permian/Triassic mass extinction
What is the 2 phase life history of amphibians?
Free living aquatic developmental stage
Terrestrial juvenile/adult stage
What is cutaneous respiration?
Where they have a reliance on water for respiration
What type of teeth did Lissamphibia develop?
A new kind of tooth called Pedicellate teeth
What are pedicellate teeth?
Teeth that have a crown and a base of dentine with an in-calcified area in between
The tooth has a crown and a pedical
As the crown wears, it breaks off and is replaced
How do tetrapods hear?
They have a layer of cells called Basilar Papilla, but they also have a larger second Amphibian Papilla
What frequencies do the two different Papilla respond to?
Basilar Papilla: 1200-1600Hz
Amphibian Papilla: 200-800Hz
Why do amphibians respond to two different frequencies?
Because they need to be able to hear in the water and on the land
What transmits sounds from the external environment to the inner ear?
Operculum-columella
How else can amphibians pick up sounds?
By muscles through vibrations that are transmitted into the inner ear
How many photoreceptors do adult amphibians typically have?
4
What are the two types of rod cells?
- “Red” rods: contain rhodopsin that responds to green light
- “Green” rods: unique to amphibians and respond to blue wavelengths
Some can pick up the UV range
What are the two types of cone cells?
- Single cones: pigment has a peak absorbance of 580nm: the yellow wavelength
- Double cones: two cones fused together- one contains rhodopsin, other contains yellow response pigment
What are the two types of skin glands on amphibian skin?
- Mucous glands: maintain moist skin for respiration
2. Granular glands: produce toxic secretions
