L9 - Amphibians and Reptiles

Question 1

When did jawless fish come along?

Answer 1

Cambrian (525 mya)

Question 2

When did jawed fish come along?

Answer 2

Silurian (435 mya)

Question 3

When did Tetrapods come along?

Answer 3

Devonian (365 mya)

Question 4

What is the origin of the tetrapods?

Answer 4

Problem with living in freshwater. 1. Oxygen depletion - adaptation : lungs (e.g. lungfish) 2. Often get choked with logs/weeds - adaptation : boned fins (e.g. lobefins). 3. More likely to dry up than oceans - adaptions : burrowing or migrating (e.g. mudskipper). 4. Lakes can get starved of food - adaptation : foraging on land.

Question 5

What are the challenges of tetrapods colonising land?

Answer 5

Gravity - aquatic life is buoyed by water, land animals need more support. Desiccation - land animals need skin to preserve their fluids. Respiration - new structures needed to breathe in air as opposed to water. Locomotion - aquatic animals can swim - motion needs modifying in land animals. Senses - light, sound and smell transmit differently in water.

Question 6

What is the age of amphibians?

Answer 6

350 - 251 mya. Many early amphibians still essentially lived in water (fish with fingers; fishapods). Had necks (skulls not attached to scapula). Still laid eggs in water and young had gills - effectively amphibians (called Lissamphibia)

Question 7

What are early tetrapods?

Answer 7

Labyrinthodonts: Derived from Rhipisistian branch of lobe-finned fish - similar skull bones, fin/wrist and teeth.

Question 8

What are early tetrapods Labyrinthodonts Acanthostega?

Answer 8

Skull bones homologous to those of fish, no attachment of hip to vertebral column, no ankles, lateral line system.

Question 9

What are early tetrapods Labyrinthodonts Pederpes?

Answer 9

‘Peter’s foot’ (354-344 mya), asymmetries in foot bones suggest it was rotated forward, more suited to terrestrial locomotion than the paddle-like feet of earlier tetrapods.

Question 10

What was the early tetrapod fin/wrist structure? page 18

Answer 10

A. Eusthenopteron, B. Gogonasus, C. Panderichthys, D. Tiktaalik, E. Acanthostega, F. Ichthyostega, G. Tulerpeton.

Question 11

What periods included great amphibian diversity?

Answer 11

Carboniferous and Permian periods. Early tetrapods were relatively large predators (niches were ecologically like modern crocodiles). Largest, Prionosuchus, was 9 metres long

Question 12

What is the class Amphibia?

Answer 12

Multiple breathing methods e.g. breathing through their skin. Permeable skin - scaleless skin highly permeable to water and oxygen. Glands - mucous (lubricates skin) and granular glands (secrete poisons). Senses - specialised auditory structures, ocular modifications. Teeth modifications - flexible pedicellate teeth.

Question 13

What is the process of respiration in amphibians?

Answer 13

They use different surfaces for gaseous exchange. Gills - all amphibians begin as aquatic larvae with gills. Cutaneous - the absorption of oxygen, and disposal of carbon dioxide, through the skin. Buccopharyngeal - occurs through the lining of the mouth. Pulmonary - breathing through their simplified lungs.

Question 14

Specific amphibians respiration of Triturus newts?

Answer 14

Use lungs and skin but skin has 75% of the respiratory capillaries.

Question 15

Specific amphibians respiration of Hyla arborea?

Answer 15

A tree frog, has 75% of the respiratory capillaries in the lungs instead.

Question 16

Specific amphibians respiration of Rana temporaria?

Answer 16

Common frog, mostly terrestrial, O2 uptake across lung is about 3x greater than skin.

Question 17

Specific amphibians respiration of Rana esculenta?

Answer 17

More restricted to water, lungs and skin function equally.

Question 18

How are the lungs used in respiration?

Answer 18

Gills dont function in air (despite high O2) because they dry out. Lungs evolved first in the common ancestor of both the Ostichthyes and the proto-tetrapod. This early lung evolved into the swim bladder seen in most actinopterygians. Amphibians lungs vary from smooth-walled salamander lungs to more subdivided frog lungs.

Question 19

How are the lungs used in respiration? pt 2

Answer 19

Reptile lungs have greater surface areas as they are subdivided into chambers. The mammalian lung has millions of alveoli (air sacs that increase surface area). However, in contrast to water flow over gills, air does not continuously enter a lung. Ventilation is achieved by muscular movements.

Question 20

What is positive pressure breathing in respiration?

Answer 20

Nares are comparable to nostrils. Nares open; buccal cavity expands air drawn in through nares. Nares close glottis opens buccal cavity contracts. Buccal cavity expands elastic recoil of lungs. Nares open glottis closed buccal cavity contracts.

Question 21

What are skin glands?

Answer 21

Skin is comprised of outer stratified epidermis and an inner spongy dermis; outer layer periodically shed, contain keratin. Inner layer has 2 types of glands: mucus (protective) and granular (poison), and various types of chromatophores.

Question 22

What are the current groups of vertebrae?

Answer 22

Amniota, tetrapoda, sarcopterygii, osteichithyes, gnathostomata.

Question 23

What group does the class Amphibia come from?

Answer 23

Sacropterygii

Question 24

What are the current groups of the class Amphibia - Caudata (salamanders & newts)?

Answer 24

10 families, 66 genera, 665 species

Question 25

What are the current groups of the class Amphibia - Gymnophiona (caecilians)?

Answer 25

6 families, 34 genera, 172 species.

Question 26

What are the current groups of the class Amphibia - Anura (frogs & toads)?

Answer 26

6 families, 539 genera, 6500 species

Question 27

What are the characteristics of Caecilians (Gymnophionia)?

Answer 27

Body greatly elongated and segmented, eyes reduced and covered with skin. Girdles and limbs absent. Protrusible sensory tentacle between eye and nostril. Legless, burrowing and aquatic with long, slender body. Earliest fossil 190 mya. Most species blind as adults, specialised sensory tentacles. Internal fertilisation (via intromittent organ) 75% viviparous, 25% oviparous.

Question 28

What are the characteristics of Salamanders (Caudata)?

Answer 28

Limbs at right angles, presence of ribs, presence of a large footplate and short stylus on the columella in most taxa. Absence of an otic notch in middle ear. Fossils 170-159 mya, all have elongated trunks and tails. Most have 4 equal-sized legs (although reduced in some aquatic species). Costal grooves facilitate water movement over body and increase surface area. Wides range of sizes, from 15mm - over 1.8m.

Question 29

What are the characteristics of Frogs (Anurans)?

Answer 29

Hind limbs longer than forelimbs, fusion of radius and ulna, fusion of tibia and fibula, elongate ankle bones (astragalus and calcaneum), absence of tail in adults, 9 or fewer presacral vertebrae. Fossils 170-159 mya, largest and most diverse group; widespread distribution, short bodies, large heads, many with long hind limbs. Reproductive modes : aquatic larvae, direct development, viviparity.

Question 30

How are Anura : frogs & toads body form linked to habitat?

Answer 30

page 37

Question 31

What are Explosive breeders (Anura: frogs & toads)?

Answer 31

Season = few days, temporary aquatic habitats, large aggregations and limited mate choice

Question 31

What are the two major breeding systems in Anura: frogs & toads?

Answer 31

Explosive breeders & Prolonged breeders

Question 32

What are Prolonged breeders (Anura: frogs & toads)?

Answer 32

Season = months, males defend territories, males outnumber females; strong mate choice.

Question 33

How does fertilisation occur in Anura: frogs & toads?

Answer 33

Fertilisation primarily occurs externally. Amplexus: embrace of male and female frog. Brings cloacae in close proximity (fertilisation). Two types of amplexus: inguinal & axillary

Question 34

What Anura: frogs & toads mating systems have eggs? How do they have these eggs?

Answer 34

Directly in water, vegetation over water (egg protection), foam nest, bromeliad nest (egg protection) (tadpole protection)

Question 35

What Anura: frogs & toads mating systems show parental care (common)?

Answer 35

Carry eggs (midwife toad), carry eggs/tadpoles (Sirinam toad), Internal brooding (morogoro tree toad).

Question 36

What % of amphibians are extinct, critically endangered/endangered, vulnerable?

Answer 36

0.6%, 20.5%, 10.1%

Question 37

Why has there been a decline in Amphibian number and diversity?

Answer 37

Climate change, anthropogenic environmental change: pollution, habitat change, introduction of invasive species. Disease: trematodes, iridovirus, chytrid fungus (Batrachochytrium dendrobatidis). Overexploitation.

Question 38

How are reptiles characterised?

Answer 38

By the presence and absence of traits. Lay hard-shelled eggs (amniotic eggs), bodies covered in scales, clawed toes, ectothermic/poikilothermic metabolism, lack of feathers of hair, heart with partially divided ventricle, respire solely with lungs.

Question 39

Why do reptiles have the amniotic egg?

Answer 39

Allow reptiles to lay their eggs in terrestrial locations, air-breathing juveniles hatch, competitive advantage over restricted amphibians.

Question 40

What is the structure of the amniotic egg?

Answer 40

Egg with protective membrane and porous shell enclosing embryo. Amnion - cushions embryo, yolk sac - contains food, allantois - stores waste; gas exchange with embryo, chorion - allows O2 and CO2 through shell.

Question 41

How do reptiles reproduce?

Answer 41

Reptile reproduction is internal, many reptiles are oviparous, some squamates are ovoviviparous or viviparous. Most reptiles do not care for their young.

Question 42

What are the characteristics of scales?

Answer 42

Tough, dry, waterproof scaly skin, develops as surface cells fill with keratin, protects against desiccation and physical injury, thin epidermis shed periodically, not homologous to dermal fish scales.

Question 43

How do reptiles respire?

Answer 43

Well developed lungs (no gills). All gas exchange done internally. Lungs partitioned to increase respiratory surface area, depend almost exclusively on lungs for respiration.

Question 44

How do respiration & circulation occur in reptiles?

Answer 44

Ventilation in reptiles (and all amniotes) based on aspiration pump. Pump acts on walls of lungs to change its shape and induce air flow in and out. Intercostal muscles move ribs, altering shape of body walls around lungs. Inhalation: ribs move out, cavity around lungs enlarges, air pressure decreases in lungs. Exhalation: ribs move in, compress lungs, expel air.

Question 45

What is the type of lung in amphibians and reptiles & birds?

Answer 45

Ancestral lung, faveolar lung (diapsid)

Question 46

What did loss of gills require in reptiles?

Answer 46

Efficient pulmonary circulation, ventricles in reptile heart developed a septum: partially divided ventricle into left/right chambers. In crocodiles, mammals and birds separation is complete. This greatly reduces mixing of oxygenated and deoxygenated blood.

Question 47

How are the heart chambers in reptiles?

Answer 47

Chambered (Septated)

Question 48

How does locomotion occur in reptiles?

Answer 48

Need to maintain center of gravity above its base of support. Most amphibians/reptiles have a broad quadrangular base of support. But when one leg is lifted the base changes to a triangle - center of gravity outside it. So lizards and crocodilians bend vertebral column.

Question 49

What are the trade off to reptilian locomotion?

Answer 49

Contraction of axial (trunk skeletal) muscles ventilates lungs. Often these muscles function in other roles (e.g. feeding/locomotion). Conflict leads to trade offs between respiration and other physiological demands. Have evolved from fish, muscles (Myomeres) used in ventilation originally functioned in locomotion. This constraint (carriers constraint) makes simultaneous breathing and locomotion difficult.

Question 50

What is the carrier's constraint in reptiles in locomotion?

Answer 50

Sideways flexing expands one lung and compresses the other. This shunts air from lung to lung. Most lizards therefore restricted to short bursts of activity.

Question 51

What are the adaptations to carrier's constraint in reptiles in locomotion?

Answer 51

Monitor lizards use positive pressure gular pumping to assist lung ventilation. Snake have asymmetrical lungs, left lung reduced. Amphibians have a sprawling stance (ancestral condition), mammals characterised by parasagittal (erect) stance, reptiles show a transition from sprawling to semi-erect (crocodiles) to parasagittal (dinosaurs)

Question 52

What is the bipedalism in reptiles?

Answer 52

The parasagittal stance evolved independently in synapsids (mammals) and archosaurs (dinosaurs/birds). Dinosaurs were the first bipeds (feature retained in birds), some lizards show intermittent bipedalism

Question 53

How are amphibian and reptiles jaws adapted?

Answer 53

Amphibian jaws adapted for quick closure but little force, reptile jaws adapted for crushing prey. Jaw muscles needed to be larger, longer and better arranged.

Question 54

Why type of jaw did the amniote ancestor have compared to mammals & ancestors and reptiles & birds?

Answer 54

Amniote ancestor - anapsid. Mammals & ancestors - synapsid, reptiles & birds - diapsid. Both have temporal fenestra

Question 55

What jaws and skull do most squamates have?

Answer 55

Most squamates have a kinetic skull, mobility of skull can increase bite force and allow them to seize and manipulate prey easier. Snakes show the most extreme kinetic skull development.

Question 56

How many orders are reptiles classified into?

Answer 56

16 orders (12 are extinct). Remaining four orders - Crocodilia, squamata (lizards & snakes), Rhymnchocephalia (1 living species). Chelonia or testudines.

Question 57

What is the order Crocodilia?

Answer 57

25 species of crocodiles, alligators, caimans and gharials. Crocodilians only remain 'reptilian' archosaur. Unchanged for 160 million years. American alligator (Alligator mississippiensis) and Saltwater crocodile (Crocodylus niloticus).

Question 58

Where are crocodiles found?

Answer 58

Africa, Asia, Americas and Australia. Alligators found in China and SE US, caimans in central america.

Question 59

How can you distinguish Alligator and crocodiles?

Answer 59

exaggerated teeth in crocodile.

Question 60

What are some types of testudines?

Answer 60

Gopher tortoise (Gopherus polyphemus), Musk turtle (Sternotherus odoratus). Kemp's ridley (Lepidochelys kempii), Leatherback sea turtle (Dermochelys coriacea), Olive ridley sea turtle (Lepidochelys olivacea)

Question 61

What are Rhynochocephalia?

Answer 61

Only 1 living species: Sphenodon punctatus (Tuatara). Endangered: <100,000 individuals left. Inhabits islands off the coast of New Zealand, resembles large lizard, diverged early in reptile evolution. A living fossil - primitive ancestral features, ancestral diapsid skull, has well developed 'third eye'.

Question 62

What are Squamata (lizards and snakes)?

Answer 62

9000 species of squamata: 3000 snakes, 6000 lizards. Snakes are effectively legless lizards. Leglessness evolved many times, broad distribution, radiated into terrestrial, aquatic and arboreal niches, most lizards are small, largest is the komodo dragon (3m).