From Biol301

• some extinct lobed finned fish leads to amphibians
• paraphyletics are intersting because they lead to descendant lineages
  • if you just use the morphological species concept it is hard not to have paraphyletic groups

Contents 1 Tetrapods 1.1 Why colonize land 1.2 Adapting to Life on Land 1.3 3 Extant Groups in Amphibia 1.4 Reptilia 1.4.1 Adaptations for dry land 1.4.2 4 Groups of Reptilia 2 Major problems with Linnean Rank System

Tetrapods

• amphibians, reptiles, birds, and mammals
• amphibians were the first vertebrates to colonize land

Why colonize land

1. Escape predators
2. New food sources
3. Less competition

Adapting to Life on Land

1. Strong muscular limbs (salamanders, crocodiles, mudsuckers)
2. Tongue: catching insects worms, etc.
3. Lungs: respiration replaces dependance on water

3 Extant Groups in Amphibia

1. Salamanders (Order Urodeles)
2. Frogs and Toads (Order Anura)
3. Legless Amphibions (Order Apoda = without legs)

Reptilia

• first to colonize real dry land (not dependant on water for sex or reproduction)
• Amnoites = reptiles, birds, mammals
• Reptiles are paraphyletic

Adaptations for dry land

1. waterproof skin (scaled and dry)
2. waterproof eggs (amiotic; do not need water for sex or eggs)
3. waterproof sex (internal fertilization and copulation)

4 Groups of Reptilia

1. Turtles (Order Chelonia)
2. Lizards and Snakes (Order Squamata)
3. Crocodiles and Alligators (Order Crocodilia)
4. Dinosaurs and Birds (Class Aves)

Major problems with Linnean Rank System

1. Many traditional groups are paraphyletic
2. Rank levels are not equivalent across groups.
3. Need for more than 8 levels

• Solutions:
  • Get rid of Linnaus' Ranks
  • Debate among yourselves about which is best.