W2 L3a - Origins of Tetrapods Flashcards
List 2 Evolutionary Mechanisms
- Genetic diversity: heritable differences in traits between organisms due to mutations, etc.
- Selection: causes heritable traits to change due to the environment
What are the 4 key transitions in the radiation of tetrapods?
Legs, Amniotic eggs, Milk and Feathers
What key transition do all tetrapods have?
Legs
Which tetrapods have the key transition: Amniotic Eggs?
The Amniotes: Mammals, Reptiles and Birds
Which tetrapods have the key transitions: Milk?
Mammals
Which tetrapods have the key transition: Feathers?
Birds
What are some of the challenges tetrapods faced transitioning on land, and what were their adaptations?
- Structural support: vertebral column, overlapping ribs, rib depth (for breathing)
- Breathing: lungs replace gills
- Circulation: 3 or 4 chambered heart
- Locomotion: Fins become limbs, dorso-ventral flattening
- Vision: position and structure of eyes
Did the adaptations of tetrapods happen all at once?
No! Occurred over millions of years
Who did the early tetrapods evolve from and when?
Sarcopterygians (lobe-finned fish) and between 380 - 365 mya
What adaptations did the fish-like early tetrapods have?
- Notochord extended into the brain-case
- Caudal vertebrae lacked zygapophyses
- Retained caudal fin
What adaptations did the amphibian-like early tetrapods have?
- Lungs
- Skull bone orientation (similar to modern amphibians)
- Weight-bearing forelimbs (weak hind limbs)
Which group filled the gap between the fish-like early tetrapods and the amphibian-like early tetrapods?
Tiktaalik
What year were the Tiktaalik discovered?
2004
What were the fish and tetrapod characteristics the Tiktaalik’s had?
Fish Characteristics: scales, fins, gills & lungs
Tetrapod Characteristics: neck, ribs, fin skeleton, flat skull, and eyes on top of the skull
How did the adaptation “fins to limb” aid tetrapods on land?
Locomotion
