Tetrapods - amphibians Flashcards
when did tetrapods first evolove
365 million years ago in the end of the devonian period
what are some problems living in fresh water and some adaptations to get around it
- oxygen depletion - lungs
- often gets choked with logs and weeds - boned fins
- more likely to dry up than oceans - burrowing or migrating
- lakes can get starved for food - foraging on land
what are some challenges to colonising land
1) gravity - land animals need more support
2) desiccation - land animals need skin preserve fluids
3) respiration - new structures needed to breathe air
4) locomotion - motions need modifying in land
5) senses - light, sound and smell transmit differently in water
how old are amphibians
350-251 million years ago
what are labyrinthodonts
refers to extinct four-limbed tetrapod’s with a large body size
- derived from rhipisistian, a branch of lobed fish
what are acanthostega
early tetrapods with skull bones homologous to those of fish
- no attachment of hip to vertebral column
- no ankles
- lateral line system
what are pederepes
an early tetrapod with asymmertries in foot bones
- more suited to terrestrial locomotion than paddle feet like earlier tetrapods
what was the largest amphibian
the prionosuchus (9 metres )
outline some characteristics of the class amphibia
1) multiple respiration methods
2) permable skin
3) glands
4) senses
5) teeth modifications = flexible pedicellate teeth
what are the different surfaces used by amphibians for respiration
1) gills
2) cutaneous = through skin
3) buccopharyngeal = lining of the mouth
4) pulmonary= breathing through simplified lungs
compare breathing between the common frog (rana temporaria) and the edible frog (rana esculenta)
common = o2 uptake across lung is 3x greater than skin
edible = more restricted to water with lings and skin functioning equally
outline the evolution of lungs for respiration
- gills dont function in air as they dry out
- early lungs evolved in the swim bladder
- lungs vary from smooth walled to more subdivide
compare lungs of reptiles and mammals
- reptiles have a greater surface area as they are subdivided
- mammalian lungs have alveoli to increase SA
- compared to water which flows over gills air doesn’t continuously enter a lung
outline the process of positive pressure breathing
1) nares (nostrils) open and buccal cavity expands and air drawn in
2) nares close and glottis opens and buccal cavity contracts
3) buccal cavity expands elastic recoil of lungs
4) nares open, glottis closes and buccal cavity contracts
what are the two types of glands found in the skin
1) mucus (protective)
2) granular (poison)
what are the current groups of amphibia
1) gymnophiona
2) caudata (salamanders and newts)
3) anura (frogs and toads)
outline some characteristics of the caudata (salamanders)
- elongated and segmented body
- eyes reduced and covered in skin
- girdles and limbs absent
- protrusible sensory tentacle bewteen eye and nostril
what are some characteristics of gynophiona
- legless, burrowing and aquatic with long slender bodies
- most species blind as adults
- ## internal fertilisation
outline some characteristics of the anurans (Frogs and toads)
- hind legs longer than forelimbs
- fusion of radius and ulna
- elongated ankle bone
- absence of tail in adults
what are the different reproductive modes in anura (frogs and toads)
- aquatic larvae
- direct development
- viviparity
what is the difference between the two major breeding systems in anura (frogs and toads)
1) explosive = a few days on tempory aquatic habitats with large aggregations and limited mate choice
2) prolonged = a few months where males defend territories and males outnumber females (strong mate choice)
define ampleux
the embrace of male and female frogs for fertilisation
what are the different mating systems
1) eggs - directly in water, vegetation over water etc
2) paretal care - carry eggs, internal brooding, viviparous
what are some explanations of amphibian extinctions
1) climate change
2) antropogenic change ie pollution, habitat change
3) diseases e.g. trematodes
4) over exploitation
