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Animal kingdom > Amphibians > Flashcards

Amphibians Flashcards

1
Q

Summary

Three groups of Lissamphibians

A

Anura
Urodela
Gymnophiona

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2
Q

Summary

Lissamphibia –

A

modern amphibians; most still have reliance on water for reproduction

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3
Q

Summary

The origin of the tetrapods in the

A

Devonian period, pre-adapted for life on land

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4
Q

What is an amphibian

A 
1. A tetrapod gnathostome
Excludes the Actinistia (coelacanths) and the Dipnoi (lungfish)
Tetrapoda
AGr tetra = “four” + pous = “foot”
All vertebrates whose ancestors had four limbs and digits
2 lineages
Lissamphibia (today)
Amniota (next week)
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5
Q

What is an amphibian

A
  1. A tetrapod gnathostome

Excludes the Actinistia (coelacanths) and the Dipnoi (lungfish)

  1. Tetrapoda
    All vertebrates whose ancestors had four limbs and digits

2 lineages
Lissamphibia [focus this deck]
Amniota

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6
Q

Preadaptation for life on land

5 points

A
  1. Lungs developed before moving onto land

outgrowths of the gut, for buoyancy and/or oxygen supply (ambient oxygen was half modern amount in the Devonian)

  1. The choanae
    Bony fish have 2 pairs of nostrils: water flows in through the forward pair, over the olfactory tissue and out through the second pair

Tetrapods have one pair, plus internal choanae which allow them to breath in through the nose

  1. Adaptations for shallow water

Flattened body and skull; paired lobed fins adapted for movement rather than anal fin

  1. Fins develop a bend at the elbow and knee
  2. Modified skull and jaw to grab food on land

Fish need to expand buccal cavity to create pressure difference

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7
Q

Tetrapods

3 points

A
  1. Earliest tetrapods were wholly aquatic, probably in brackish water
  2. The Late Devonian extinction (c. 370 Mya) killed off all fish-like tetrapods and left only those adapted to terrestrial existence
    Some later returned to aquatic lifestyle
  3. Later adaptation
    Placement of eyes on head: heads become tall and narrow again

Head and neck mobility: fish lack necks

Fused sacrum: connects pelvis and hindlimbs

Loss of gills, tail fins, lateral lines

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8
Q

Labyrinthodonts

A
  1. Ancestral to all extant land-living vertebrates
  2. Name (“maze-tooth”) refers to infolding of dentine and enamel
  3. Heavily armoured skulls and complex vertebrae

Ichthyostegalia
Reptiliomorpha

Temnospondyli
Lepospondyli [one of these 2 ancestor of modern amphibians]

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9
Q

“Amphibia” included

A

all extinct and modern amphibians

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10
Q

Lissamphibia includes

A

just modern day frogs, salamanders, and caecilians

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11
Q

Modern Amphibians
Lissamphibia
3 points

A
  1. Anura: frogs and toads
  2. Urodela: salamanders and newts
  3. Gymnophiona: caecilians

Most of the differences between these groups are down to different modes of locomotion

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12
Q

Modern Amphibians
Lissamphibia
Common ancestor probably possessed:
6 points

A
  1. Pedicellate teeth (have a crown and base/pedicel of dentine)
  2. Operculum-plectrum complex to transmit sounds to the inner ear
  3. Skin with mucous cells (keep skin moist) and granular cells (produce poison)
  4. A two-channel sensory area in the inner ear to pick up high and low frequencies
  5. Ability to elevate eyes with levator bulbi muscles
  6. Fat bodies located near gonads
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13
Q

Body Plan

3 points

A
  1. Evolved from a salamander-like body plan
  2. Skin has cornified layer but is permeable to water
    Moulted in one piece
    Gas exchange takes place through skin
    Mucous glands keep skin moist
    Granular glands secreted distasteful or poisonous substances
  3. Hollow bones
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14
Q

Respiration

3 points

A
  1. Lungs are simple compared to amniotes

Large alveoli, few internal walls

Less efficient: oxygen diffuses slowly

Use buccal pumping rather than ribs to ventilate

  1. Cuticular respiration

Requires water layer

More efficient at lower temperatures (oxygen concentration goes up)

  1. Larvae have external gills
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15
Q

Circulation

2 points

A
  1. Two-chambered heart in larvae (like a fish)

Only pumps deoxygenated blood

  1. Three chambered heart in adult

One ventricle, two atria

Some mixing of oxygenated and deoxygenated blood

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16
Q

Digestion

4 points

A
  1. All living species are carnivorous

Few morphological specialisations

  1. Most catch prey with sticky tongue
  2. Inertial feeding to assist with swallowing, plus eyeballs
  3. Large liver stores glycogen, also possess fat bodies near kidneys
17
Q

Excretion

2 points

A
  1. Kidneys are dorsal; filter blood with high pressure system
  2. Excrete urea due to need to conserve water

Some tree frogs excrete uric acid (can be even drier)

Larvae excrete ammonia

18
Q

Nervous system

2 points

A
  1. Brain is equal parts cerebrum, midbrain, and cerebellum

2. Pineal body controls hibernation and aestivation

19
Q

Senses

3 points

A
  1. The operculum-plectrum complex is responsible for transmitting both vibration and sound
  2. Papillae amphibiorum and papillae basilaris detect sound at different frequencies
  3. Larval amphibians retain lateral line
20
Q

Reproduction

A
  1. Usually requires fresh water

Some tropical frogs have direct development (tadpoles do not emerge from eggs)

  1. Frogs use external fertilisation
    Male grasps female (amplexus)
  2. Salamanders and caecilians use internal fertilisation

Male salamanders produce a spermatophore; the female takes it up

male caecilian uses an intromittent organ

  1. Metamorphosis regulated by thyroxine and prolactin
21
Q

Anura
Frogs and toads
3 points

A
  1. Urostyle formed of fused vertebrae

9 presacral vertebrae

Long, forward-sloping ilium in pelvis

Lower jaw without teeth

Frontoparietal bone between eyes

  1. Earliest fossil is early Triassic (250 Mya)
  2. No biological difference between frogs and toads
22
Q

Urodela
Salamanders
5 points

A
  1. Slender bodies with blunt snouts

Short limbs projecting at right angles, digit and/or limb reduction

Tail in both adult and larval forms

  1. Earliest fossil is Middle Jurassic (c. 170 Mya)
  2. Reduction of toes, amphiumas have reduced legs, sirens have no hind limbs
  3. Extreme self-defence
  4. Caudal autotomy & puncturing ribs
23
Q

Gymnophiona
Caecilians
7 points

A
  1. Eyes only detect light dark,
  2. have a pair of tentacles between eyes and nostrils
  3. Adaptations to burrowing lifestyle

Completely lack limbs, tails may be absent

Skin has ring-shaped folds as
well as scales containing calcite

Strong skull with pointed snout

  1. Most are viviparous, giving birth to well-developed offspring
  2. One egg-laying species feeds its own skin to newly-hatched young
  3. Live in wet, tropical regions
    Eat soil-dwelling invertebrates, particularly worms
  4. One aquatic family has an eel-like fin

Animal kingdom (14 decks)

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