Lissamphibia Lecture Flashcards
What issue do terrestrial vertebrates face in terms of reproduction?
Desiccation of eggs. Terrestrial vertebrates have evolved methods of internal fertilization and gestation to overcome this.
If a frog is trying to hear a high frequency sound, what will happen in its ear?
The opercularis muscle will contract, causing low frequency vibrations to not be transmitted and only high frequency vibrations will be transmitted to the Papilla basilaris for detection.
If a frog is trying to hear a low frequency sound, what will happen in its ear?
The columellaris muscle will contract, causing high frequency vibrations to not be transmitted and only low frequency vibrations will be transmitted to the Papilla amphibiorum for detection.
What do the Hedonic glands in frogs secrete?
Pheromones
What benefits do mucous secretions in frogs have?
-Evaporative cooling
-Oxygen uptake and CO2 disposal
-Mating
-Prevents desiccation
-Antimicrobial
How can frogs breathe through their skin?
Mixed blood is pumped from the right side of the heart through the cutaneous artery, which takes it to the capillary beds in the dermis where the blood can then pick up oxygen and dispose of CO2. This mechanism is also seen in their buccal cavity.
How is oxygenated and deoxygenated blood kept separate in an Anuran heart?
The shape of the ventricle is able to be manipulated to segregate oxygenated and deoxygenated blood
When do Anurans utilize cutaneous respiration?
When they are underwater. Because of this, they can spend extended periods of time underwater without having to surface
Which hormone is responsible for inducing metamorphosis?
Thyroxine released by the thyroid
What is the hormone called that acts as a negative feedback to delay metamorphosis?
Prolactin released by the pituitary
How do salamanders reproduce?
A male deposits a spermatophore, then uses specific behaviours to rub pheromones secreted by hedonic glands onto the female, causing her to ovulate and pick up the spermatophore. Fertilization is internal.
What characteristics does the ancestral form of an Anuran have?
-More toes (5 instead of 4)
-Specialized and short pelvis
-No urostyle
-Trunk is longer
-Short hindlimbs and toes
What does a long forelimb length indicate?
That the frog is likely more of a walker
What does a long hindlimb length indicate?
That the frog is likely a long-distance jumper
Why do frogs crouch?
The reduce their surface area, thereby reducing water and heat loss
What are some parental care strategies used by frogs?
-Guarded by male
-Make a foam that defends and prevents the eggs from drying out
-Folded into a leaf
-Eggs carried on the frogs back
-Eggs carried in the vocal sacs
What are some reasons that frogs use calls?
-Mating
-Defending territory
-Warnings
What are some costs/risks associated with calling?
-Attracting predators
-Water loss
-Energetically costly
What types of mouths can tadpoles have?
-Superior (surface feeding)
-Terminal (filter)
-Subterminal (bottom feeder)
-Suction (scrapes algae)
-Siphon (passive filter feeding)
Why do Caecilians have skulls with very few holes?
Because of their digging lifestyle. More holes would lead to fractures in the skull
What threats do amphibians face?
-Habitat loss
-Climate change
-Pollution
-Disease (chytridiomycosis)
What body systems must be modified to sustain the transition to land?
Desiccation, musculature, waste excretion, sensory systems, reproduction, respiration, and thermal control
What are the skeletal modifications necessary for the transition to land?
Development of the neck and zygapophyses, development of sacral vertebrae, paired fins into paired limbs, development of an ankle joint, and fin elements into digital elements
What are zygapophyses?
Paired bony projections that extend from the vertebrae in the spine of vertebrates
In the development of the neck, what was lost?
The posttemporal-supracleithrum-postcleithrum articulation
If humans had an posttemporal-supracleithrum-postcleithrum articulation, what would be the equivalent?
Our shoulders would be attached to our ears
Describe the function of the zygapophyses
They serve an important function by interlocking with adjacent vertebrae, providing stability and preventing excessive twisting or bending of the spinal column
True/False? The pectoral girdle and the pelvic girdle have increased association with the surrounding structures in tetrapods
False. The pectoral girdle has decreased association and the pelvic girdle has increased association with the sacral vertebra
Which side of your hand is the postaxial side?
Pinky
Which side of your hand is the preaxial side?
Thumb
As fins developed into limbs, what happened to the axis of symmetry? What is this called?
The axis curved downwards towards the preaxial side. This is called postaxial displacement
What is responsible for the plethora of digits on Acanthostega’s limb?
Hox genes
True/False? All ankles within Tetrapoda have very similar structures
True
True/False? All paired fins are found on either the pectoral or pelvic girdles
True
What are the main modifications of the muscular system during the transition to land?
Decrease of epaxial muscle mass
Subdivision of hypaxial musculature
Where is epaxial muscle located on the body?
Dorsal side
Where is hypaxial muscle located on the body?
Ventral and lateral sides
What do strong zygapophyses limit?
Lateral undulation
What is the main function of hypaxial musculature after subdivision?
Fine-tuning of limb movement
Hypaxial muscles subdivided from ___ to ____ muscles
Two, five
What are the main modifications of the cardiovascular and respiratory systems during the transition to land?
Development of upper trachea
Ribs and mechanical exhalation
Double-circuit circulation
What is the pneumatic duct involved in? What is it homologous to?
It is the duct that leads from the stomach to the gas/swim bladder in physostomous fish. Homologue of the trachea
How do early amphibian tracheas differ from our tracheas?
Lack cartilaginous rings
The ribs in an early tetrapod, Eryops, go from pointed to blunt from front to back. What function does this serve?
This allows for some connective tissue to fill in the gaps, as well as exhalation with the compression of that side of the body
The small ribs of Acanthostega suggests what? What does the flange suggest?
Little protection for the internal organs up on land; internal gills and soft tissue operculum
The robust ribs of Ichthyostega suggests what? What does the robust pectoral girdle suggest?
More internal organ protection from gravity when on land; internal gills
When an amphibian bends to the left, what happens to the air in its lungs?
The left lung gets compressed (positive pressure) by intercostal muscles, while the right lung gets expanded (negative pressure), so air goes from the left lung to the right lung
True/False? Costal ventilation can be used for both inhalation and exhalation
False. Only for exhalation
What challenge do single-circuit organisms face when out of the water?
The pooling of blood due to low blood pressure and lack of support for gravity
Describe a double-circuit circulatory system
The heart has two entrances in which deoxygenated blood is pumped to the lungs and then is pumped to the rest of the body by the other side of the heart
Why is having a double-circuit system more beneficial to have on land?
Having a separate pulmonary system allows for the high blood pressure necessary to fight gravity
What is one of the challenges caused by a double-circuit system? How is this avoided?
High blood pressure may cause issues with the thin blood vessels found in the lungs. This is prevented by having the blood pumped first to the lungs, then to the rest of the system, rather than just all at once, also thinker vessels
What germ layer forms the bladder?
Mesoderm
What are the modifications in the excretory system during the transition to land?
Development of a urinary bladder
Primitive kidney
What advantages does having a urinary bladder give terrestrial species?
Concentration of ammonia so less frequent urination. This also prevents pheromones and other smells from being released all the time, which would make it easier for predators to find these species
True/False? Primitive amphibians had fully developed kidneys
False. Their “kidneys” ran throughout their entire body system
What is an advantage of having kidneys?
Allows for the high concentration of solutes in one particular area of the body instead of a low concentration throughout the body. This allows for greater water reabsorption
Which sensory systems are affected by the transition to land? Why?
Vision, hearing, and olfaction. Change in density of the medium they occupy (dense to light)
In which ways to the fish and amphibian eyes differ?
Fish: ciliary muscles move the lens in any direction, lens is spherical
Amphibians: ciliary muscles change the shape of the lens by stretching it, lens is oval
Air has a lower refractive index than water. Why is this important to consider in relation to the eyes of fish vs. amphibians?
The lenses of fish do not have to change shape in order to focus light in a certain area as the refractive index for the lens is the same as the water, so the light doesn’t get refracted. On the other hand, amphibians have to change the shape of their lenses to accommodate for the difference in refractive indexes
The hyomandibula is a homologue of what structure?
Stapes (ossicle) and ventromedial portion of Columella
Describe the path sound waves take in water for teleosts
Sound travels through the body of the fish into the swim bladder, where it gets redirected to the inner ear by Weberian ossicles
Describe the path sound waves take on land for teleosts. Why does this occur?
Sound will reflect off the body of the fish as air and the body of the fish are different densities