Amphibians Flashcards
Briefly Explain the formation of sound in frogs
-Sounds are produced as air from lungs passes repeatedly between the larynx and elastic sacs in the throat
- the shape and resonance of vocals sacs amplifies and disperses the sound(ventriloquial quality making frogs difficult to locate)
- xenopus (platanna) lack vocal sacs
In point form describe the process of sound production in frogs
-lungs inflated to greater capacity than during normal breathing
- air rapidly moves from lungs to buccal cavity causing vocal cords of larynx to vibrate
- sound produced intensified by thin walled extension of buccal cavity- vocal sac
- most air is vocal sac then moved back to lungs and utilised repeatedly in production of subsequent calls
Name and explain the 3 broad groups of vocal sacs
-median sub gular sac - single sac located beneath the throat(majority of SA frogs)
- paired sub gular sac- sac has two lobes separated by median partition(water Lily frog)
- paired lateral sacs - sacs are thin membranous structures on slits on the side of the head behind below angle of the jaws(ornate frog)
Explain how platannas(xenopus) produce sound
-No real vocal sacs
- sound produced from below surface of water
- popping/clicking sounds produced by movement’s of modified laryngeal cartilages against one another
Briefly Explain frog environmental adaptation
-Frogs obtain considerable proportions of oxygen through their skin and excrete Carbon dioxide in the same way
- for this reason skin must stay permanently moist given that oxygen cannot diffuse into blood unless dissolved in water
How do frogs maintain the essential dampness of their skin ?
-certain glands in the skin which produce special secretions
- frogs habitat of swimming
- living in wet surroundings
Name the two factors that are relevant to the life of frogs involving the environment
- dehydrating air environment and replenishment of lost water
- flooding of the body due to continual influx of water through process of osmosis
Explain how different frogs are adapted to survive in their specific environments
-Platannas need to continually deal with hydration due to the aquatic environment they live in while sand frogs have to deal with severe desiccation
- frogs that spend time both on land and in water have to cope with both extremes
- even though some water lost through urine and air exhaled from lungs, the skin is the major organ of the frog involved in both gain and loss of water
- skin mainly used for oxygen uptake and must stay moist
- frogs specially adapted to their environments( frogs from dry regions tolerate water loss better than others)
Explain the behaviour of frogs to help them adapt to evaporative conditions in the environment
-Some frogs forage in day time under leaves and hide away from sun
- some reduce the amount of their body surface exposed to the air by tucking their limbs and digits beneath their body, typical hunched up posture.
- others retreat under stoned or leaves where water is gained rather than lost
-Bullfrogs have a unique adaptation to water-loss during their hibernation, a number of moulted skin layers are retained around the body and form a thick parchment- like cocoon
Do frogs actively drink water and how does water absorption work ?
-They do not
- water is absorbed across the skin
- granulation of skin of frogs belly and limbs increase the surface area and enhances water uptake
- body well supplied with blood vessels that further aid in respiration
Explain what is ment by frogs being ectothermic
- depending on environmental heat sources rather than metabolic heat sources to maintain body temperatures
- most frogs will try and avoid high temperatures by moving away into ground or inti water
- restrict hours of activity to darkness to avoid high daytime temperatures
-heat gained from environment lost through evaporation of water from the skin - many frogs can adapt to a wide range of temperatures given that there is no water stress
Explain the process of moulting of frogs
- skin consists of two later ls, epidermis(outer) and dermal(inner)
- epidermis exposed to environment and is protective layer, consists of dead cornified cells which shed periodically during process of moulting and replaced by a new layer that develops underneath
- frogs moult on a regular basis throughout the year, every 4-11 days
- moulted skin immediately eaten
Give an example of a environmental adaptation in foam nest tree frogs
- water loss due to evaporation through skin is low except in hot conditions where sweat cools them down
- considerable water economy achieved through excretion in form of uric acid with loss of very little water
- this allows the frog to bask in full sunlight and enable them to hibernate in exposed places for many months in the dry season
Name and explain the various frog defence mechanisms
- frogs rely heavily on avoiding detection by means of camouflage
- frogs will attempt to escape once detected by immediately leaping away ,this may :
•take the frog to an inaccessible area to the predator
•to again become concealed by remaining still
• confuse predators by first jumping into the water and then out again
• using scent trails that are interrupted by jumping to hamper detection
-frogs that can not rapidly escape will increase there apparent size by inflating their lungs with air - increase in size also often accompanied by secretions of defensive parotid
- bullfrogs gape and might bite
- many species resort to death feigning(thanatosis)
- a number of frogs eject a large amount of water from bladder
Elaborate on the “poisonous” frogs in south africa
Several frogs secrete substances to deter predators
toads have parotid glands which secrete a whitish liquid that is distasteful and cardiotoxic(cause hallucinations and heart failure)
platanna exude slippery mucous which besides makes it difficult to hold on to also is toxic(birds scrape it of before eating)
rain frogs secrete large amounts of adhesive liquid which is also toxic
banded rubber frogs secrete toxic fluid from skin that will cause a rash in sensitive skin or excruciating pain if it gets onto abrasions or the eyes
