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VETS1060 > Tetrapods, Amphibians & Amniotes > Flashcards

Tetrapods, Amphibians & Amniotes Flashcards

1
Q

Define tetrapod

A

four-footed

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2
Q

Tetrapods include

A

Amphibians, reptiles,
birds & mammals

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3
Q

Tetrapod adaptations to terrestrial existence

A
  • More ossified limbs, pelvis & pectoral girdle
  • Larger articulations of vertebral column to avoid sagging
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4
Q

Define more ossified

A

More rigid, hardened, and resistant to change

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5
Q

What do modern amphibians represent?

A

An intermediate, but highly specialised group in the transition from water to land

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6
Q

What did modern amphibians arise from?

A

The labyrinthodonts

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7
Q

What does Acanthostega mean?

A

Four footed fish

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8
Q

Define extant

A

Still in existence; surviving.

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9
Q

What do many ancestral tetrapods and modern amphibians have in common?

A
  • Aquatic as juveniles & terrestrial as adults
  • Have a lateral line system
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10
Q

What is a lateral line system?

A

Enables determination of position in water currents

In fish:
- Aquatic sensory system

In amphibians:
- Present in amphibian larvae, lost at metamorphosis

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11
Q

What were Acanthostega thought to have?

A
  • Radial fin rays supporting a tail fin
  • Defined limbs with digits (8)
  • Weight-bearing girdles
  • Internal gills
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12
Q

When did modern amphibians arise?

A

200 million years ago (Jurassic)

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13
Q

What are the 3 extant orders of ampbibians?

A
  1. Anura
  2. Urodela/Caudata
  3. Gymnophiona/Apoda
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14
Q

Order Anura includes:

A
  • Frogs
  • Toads
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15
Q

Order Urodela/Caudata includes:

A
  • Salamanders
  • Newts
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16
Q

Order Gymnophiona/Apoda includes:

A

Caecilians, which are;
- Legless, blind
- Aquatic or subterranean

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17
Q

Which organism most closely resembles ancestral amphibians?

A

Salamanders due to their long body, short legs, and well-developed tail

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18
Q

In amphibians, what happens when aquatic larvae that metamorphose into terrestrial adults?

A
  • Lose lateral line system
  • Lungs replace gills
  • Develop legs
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19
Q

Which ancestral characteristics do amphibians retain?

A
  • Inhabit aquatic or damp habitats that are tropical & temperate
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20
Q

Ancestral amphibians had __ and evolved from ___

A

Scales; lobe-finned fishes

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21
Q

What is the stratum corneum?

A

The outermost layer of the epidermis, the skin’s protective barrier

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22
Q

What is a major characteristic of modern amphibians?

A

Very thin stratum corneum resulting in;
- Limited protection from abrasion & dehydration
- Cutaneous respiration

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23
Q

Why do amphibians have such a thin stratum corneum?

A

To allow for cutaneous respiration

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24
Q

What percentage of gas exchange can salamanders perform through their skin

A

100%

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25
What percentage of gas exchange can frogs and toads perform through their skin
50%
26
How do amphibians facilitate cutaneous respiration?
- Via capillary beds within epidermis - The only instance in vertebrates where blood vessels are so close to the skin - Large surface area to body mass ratio
27
Vertebrae in amphibians
- Articular processes - Interlock - Provide rigidity & support out of water
28
Amphibious adaptations to a terrestrial existence
1. Vertebrae 2. Pectoral Girdle 3. Pelvic Girdle 4. Digits 5. Mucous glands 6. Granular glands 7. Chromatophores 8. Eyelids & tear glands
29
Pectoral Girdle in amphibians
- No longer joined to the skull - Development of cervical vertebrae - Free movement of the head
30
Pelvic Girdle in amphibians
- Ilium, ischium & pubis (urostyle) - Sacral region - Articulates with pelvic girdle
31
Digits in amphibians
- 5 digits on hindlimbs, 4 digits on forelimbs
32
Integument
A tough, outer protective layer
33
Mucous glands in amphibians
- Continuous secretion - Helps prevent dehydration - Limited role in preventing entry of pathogens
34
Granular glands in amphibians
- Poison glands - Milky, distasteful secretion - Often toxic if ingested or injected - Neurotoxins, haemolysins, hallucinogens… - Poison dart frogs secrete alkaloids in poison - Amphibians do not synthesise alkaloids - Ingest them in insects & sequester in glands
35
Chromatophores in amphibians
- Predominantly within the dermis - May also be present within the epidermis - Noxious skin secretions often coupled with striking colouring – e.g. poison dart frogs - Aposematic colouration
36
Eyelids & tear glands in amphibians
- Develop at metamorphosis
37
Aposematic colouration
A conspicuous display of bright colours or patterns used by animals to signal to predators that they are poisonous, venomous, unpalatable, or otherwise dangerous.
38
Reproduction in frogs and toads
- External fertilisation - Most return to water to reproduce - Female releases eggs - Male deposits sperm over the eggs
39
Reproduction in caecilians
- Fertilisation is internal - Male & female press cloacae together & sperm transferred into female’s cloaca
40
Reproduction in salamanders
- Fertilisation is internal - Male produces a spermatophore (cap of sperm on a gelatinous stalk) - Female picks up with cloaca
41
When is the lateral line present in amphibians?
Present in aquatic larvae, lost in terrestrial adults
42
What did the evolution of the amniotic egg do?
Facilitated the success of vertebrates on land
43
What was a key adaptation for a terrestrial existence in amniotes?
Evolution of the amniotic egg facilitated the
44
Groups of amniotes
- Reptiles - Birds - Mammals
45
Characteristics of the amniotic egg
- Presence of several extraembryonic membranes - Fluid filled amnion which encloses the embryo; and protects it from mechanical shock - Allantois which contains fetal urine; contributes to placenta in eutherian mammals - Chorion – outer envelope; contributes to placenta in eutherian mammals - Yolk sac – source of nutrition for embryo
46
The embryo in birds and reptiles
Enclosed by a calcareous or leathery shell to prevent desiccation
47
What adaptation do Eutherian & marsupial (therian) mammals have from birds and reptiles??
They have lost the shell - Eutherians form a placenta - Marsupials deliver altricial young
48
Gestation versus lactation
- Gestation is the period of pregnancy, from conception to birth, when the fetus develops within the mother's uterus. - Lactation is the process of producing and secreting milk from the mammary glands after birth
49
What similarities do monotremes have to birds and reptiles?
Monotremes have retained the egg shell
50
What are Cotylosauria?
- "Stem reptiles” or the basal group of amniotes
51
What are the two major lineages in the evolution of the amniotes?
1. Sauropsida 2. Synapsida
52
Sauropsids include:
- Dinosaurs - Modern reptiles - Birds
53
Synapsids include:
- Mammals
54
Skull Fenestration
The presence of openings, or windows, in the temporal region of the skull.
55
How can amniotes be grouped?
According to the anatomy of the temporal region of the skull - Number of temporal fenestrae
56
Groups according to skull fenestration:
1. Anapsid 2. Diapsids 3. Synapsid
57
Anapsids have ___ and include:
- No fenestrae - Ancestral amniotes - Turtles & tortoises
58
Diapsids have ___ and include:
- Two fenestrae - Dinosaurs, lizards, snakes, crocodiles, tuatara & birds
59
Synapsids have ___ and include:
- One fenestra - Mammals
60
Summarise the evolution of Amniotes:
Although extant amphibians and reptiles retain many ancestral features, they have evolved a vast array of extraordinary adaptations that have enabled them to survive to the present day.

VETS1060 (19 decks)

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