Clade Tetrapods Flashcards
Clade Tetrapods
Third surviving lineage of lobe-fin fish in Clade Osteichthyans characterized with fleshy, muscular pectoral and pelvic fins connected by bony elements
Vertebrates with two pairs of sturdy skeleton-supporting limbs with feet and digits
include transition to land
Limbs Evolution
Transition from water to land in tetrapods where limbs and feet evolved from lobe-finned fish
Limbs are three-parted
1. upper single long bone hinged to
2. pair of parallel long bones
3. terminal hand/foot with jointed digits
Why did Vertebrates evolve life for land?
- Early colonization by other organisms like plants and invertebrates that provided food
- Environmental changes: continental drift creating wide range of habitats
- Ecological pressures of competition and predation
Challenges of Terrestrial Life for Aqautic-Adapted Organisms
- Gravity: require supporting tissues
- Water conservation: need protective skin and a way to protect embryos
- Reproduction: spawning and fertilization not suitable for air
- Gas Exchange: Gills desiccate upon exposure to air
- Locomotion: lateral side-to-side movement inefficiant
- Sensory Perception: light, sound, and smell transmit differently in air
- Temperature regulation: temp fluctuations are more pronounced in air than water
Adaptations critical for Tetrapod transition to Land
- Vertebral column
- Mineralized skeleton and paired lateral fins from clade gnathostomes
- Simple lungs from Clade Osteichthyans
- Bony, muscular pectoral/pelvic fins
- Internal nostrils
The Tiktaalik Discovery
discovery of transitional fossil linking fishes and tetrapods
fish traits: scales, lobe fins lacking digits, both gills and lungs
tetrapod traits: neck structure with separated shoulder, rib configuration, limb skeleton, flattened skull, and eyes on top of head
Tetrapod Shared Derived Traits
- Four limbs with feet and digits adapted for locomotion and weight bearing
- Distinct neck enabling independent head movement
- Fusion of pelvic girdle to vertebral column for stability and terrestrial locomotion
- Absence of gills
- Ears for airborne sounds
Two Extant Groups of Tetrapods
- Amphibia
- Amniota
