Tetrapods Flashcards
When did the first Tetrapods emerge?
Devonian.
What group are the Tetrapods part of?
Sarcopterygii.
What were the advantages of land?
Increase in range of habitats and food.
Avoid aquatic predators and competition.
More oxygen.
Raise body temperature and metabolic rate.
What were the disadvantages of leaving water?
- 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.
How did tetrapods get support on land?
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.
Give Tetrapod characteristics.
- 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.
Give fish-like characteristics of Tiktaalik.
Gills and lungs.
Fins.
Scales.
Primitive jaws.
Give land-living animal characteristics of Tiktaalik.
Neck.
Wrists.
Skull with eyes on top.
Expanded ribs.
Give the four important tetrapods and their stage in evolution.
- Euthenopteron - lobe finned fish.
- Tiktaalik - transitional.
- Acanthostega and ichthyostega - digits.
What were the three major events for living on land?
- Evolution of limbs with digits.
- Evolution of walking.
- Evolution of terrestriality.
Give characteristics of Acanthostega.
- No wrists and ankles.
- Paddle-like limbs.
- 8 digits.
- Internal gills.
- Limbs and spine do not support much weight.
Give characteristics of Ichthyostega.
- 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.
How did skulls evolve to breathe on land?
- 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.