Tetrapods Flashcards

1
Q

When did the first Tetrapods emerge?

A

Devonian.

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2
Q

What group are the Tetrapods part of?

A

Sarcopterygii.

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3
Q

What were the advantages of land?

A

Increase in range of habitats and food.
Avoid aquatic predators and competition.
More oxygen.
Raise body temperature and metabolic rate.

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4
Q

What were the disadvantages of leaving water?

A
  • Gravity, body needs support for locomotion and to prevent collapse.
  • Need lungs for land.
  • Skin must resist desiccation.
  • Greater fluctuations in temperature.
  • Sense organs respond to different simuli.
  • Blood needs to pump harder.
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5
Q

How did tetrapods get support on land?

A

Modification of paired fins, pelvic and pectoral girdles, vertebrae and the loss of skull bones freeing shoulder from skull, allowing a flexible neck.
- Also strengthening of muscles.

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6
Q

Give Tetrapod characteristics.

A
  • Paired hind and forelimbs.
  • Pectoral girdle separated from skull, mobile neck.
  • Hyomandibular bone becomes stapes, conducting sound to ear.
  • First cervical vertebra modified to allow skull movement.
  • Flatter eye lenses than fish.
  • Eyes on top of head, kept moist with eyelids.
  • Double circulation.
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7
Q

Give fish-like characteristics of Tiktaalik.

A

Gills and lungs.
Fins.
Scales.
Primitive jaws.

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8
Q

Give land-living animal characteristics of Tiktaalik.

A

Neck.
Wrists.
Skull with eyes on top.
Expanded ribs.

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9
Q

Give the four important tetrapods and their stage in evolution.

A
  • Euthenopteron - lobe finned fish.
  • Tiktaalik - transitional.
  • Acanthostega and ichthyostega - digits.
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10
Q

What were the three major events for living on land?

A
  • Evolution of limbs with digits.
  • Evolution of walking.
  • Evolution of terrestriality.
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11
Q

Give characteristics of Acanthostega.

A
  • No wrists and ankles.
  • Paddle-like limbs.
  • 8 digits.
  • Internal gills.
  • Limbs and spine do not support much weight.
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12
Q

Give characteristics of Ichthyostega.

A
  • Vertebral column.
  • Bony projections called zygapophyses which help support spine in absence of water.
  • Overlapping ribs prevent crushing of lungs, inhibit side-to-side movement.
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13
Q

How did skulls evolve to breathe on land?

A
  • Elongate snout, fewer bones, stronger sutures.
  • Strong bones at back of head for muscle attachment.
  • Fusing lower jaw bones for buccal pump. Mouth cavity bellows-like action, gulping air to force it into lungs.
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