Tetrapods - amphibians

Question 1

when did tetrapods first evolove

Answer 1

365 million years ago in the end of the devonian period

Question 2

what are some problems living in fresh water and some adaptations to get around it

Answer 2

• 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

Question 3

what are some challenges to colonising land

Answer 3

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

Question 4

how old are amphibians

Answer 4

350-251 million years ago

Question 5

what are labyrinthodonts

Answer 5

refers to extinct four-limbed tetrapod’s with a large body size
- derived from rhipisistian, a branch of lobed fish

Question 6

what are acanthostega

Answer 6

early tetrapods with skull bones homologous to those of fish
- no attachment of hip to vertebral column
- no ankles
- lateral line system

Question 7

what are pederepes

Answer 7

an early tetrapod with asymmertries in foot bones
- more suited to terrestrial locomotion than paddle feet like earlier tetrapods

Question 8

what was the largest amphibian

Answer 8

the prionosuchus (9 metres )

Question 9

outline some characteristics of the class amphibia

Answer 9

1) multiple respiration methods
2) permable skin
3) glands
4) senses
5) teeth modifications = flexible pedicellate teeth

Question 10

what are the different surfaces used by amphibians for respiration

Answer 10

1) gills
2) cutaneous = through skin
3) buccopharyngeal = lining of the mouth
4) pulmonary= breathing through simplified lungs

Question 11

compare breathing between the common frog (rana temporaria) and the edible frog (rana esculenta)

Answer 11

common = o2 uptake across lung is 3x greater than skin

edible = more restricted to water with lings and skin functioning equally

Question 12

outline the evolution of lungs for respiration

Answer 12

• gills dont function in air as they dry out
• early lungs evolved in the swim bladder
• lungs vary from smooth walled to more subdivide

Question 13

compare lungs of reptiles and mammals

Answer 13

• 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

Question 14

outline the process of positive pressure breathing

Answer 14

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

Question 15

what are the two types of glands found in the skin

Answer 15

1) mucus (protective)
2) granular (poison)

Question 16

what are the current groups of amphibia

Answer 16

1) gymnophiona
2) caudata (salamanders and newts)
3) anura (frogs and toads)

Question 17

outline some characteristics of the caudata (salamanders)

Answer 17

• elongated and segmented body
• eyes reduced and covered in skin
• girdles and limbs absent
• protrusible sensory tentacle bewteen eye and nostril

Question 18

what are some characteristics of gynophiona

Answer 18

• legless, burrowing and aquatic with long slender bodies
• most species blind as adults
• ## internal fertilisation

Question 19

outline some characteristics of the anurans (Frogs and toads)

Answer 19

• hind legs longer than forelimbs
• fusion of radius and ulna
• elongated ankle bone
• absence of tail in adults

Question 20

what are the different reproductive modes in anura (frogs and toads)

Answer 20

• aquatic larvae
• direct development
• viviparity

Question 21

what is the difference between the two major breeding systems in anura (frogs and toads)

Answer 21

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)

Question 22

define ampleux

Answer 22

the embrace of male and female frogs for fertilisation

Question 23

what are the different mating systems

Answer 23

1) eggs - directly in water, vegetation over water etc

2) paretal care - carry eggs, internal brooding, viviparous

Question 24

what are some explanations of amphibian extinctions

Answer 24

1) climate change
2) antropogenic change ie pollution, habitat change
3) diseases e.g. trematodes
4) over exploitation