Lecture 17 - chordates II - IV The reptiles A Extant...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
Lecture 18 – Chordates II I. The evolution of legs A. Tiktaalik 1. Has many fish-like traits (e.g. fins, scales, primitive jaws) 2. Has tetrapod-like traits (e.g. fins with wrist, neck, expanded ribs) B. Duplication of hox genes coding for tail create set new sets of appendages (i.e. legs) C. Digit number highly variable in early tetrapodomoph legs II. Evolution of Amphibians A. Important traits 1. Breath through lungs, gills and skin 2. Fertilization external 3. Reproduction tied to water III. Evolution of the Amniotes A. Amniotic egg 1. Amnion - protects and provides shock absorbtion 2. Yolk sac- stockpile of nutrients for embryo 3. Allantois - disposal sac for metabolic waste 4. Chorion - allows for respiration across shell B. Reproduction independent of water C. B. Internal fertilization D. Legs rearranged for carrying weight out of water
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Background image of page 2
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: IV. The reptiles A. Extant reptiles (Turtles, crocodilians, birds, tuatara and squamates) B. Extinct reptiles (pterosaurs, dinosaurs, plesiosaurs and ichthyosaurs) V. The mammals - produce milk, have hair A. Monotremes 1. Lay eggs, produce milk (but no nipples) 2. E.g. platypus and echidna B. Marsupials Lecture 18 – Chordates II 1. Rudimentary placenta, nipples 2. Pouch for fetal development 3. e.g. kangaroos, opossum C. Eutherians 1. Complex placenta 2. e.g. rodents, whales, bats, primates, elephants) 3. Primates a. Derived traits 1. Opposable thumb 2. fingerprints 3. large brain b. Two groups 1. Prosimians (e.g. lemurs and tarsiers) 2. Anthropoids (monkeys and apes) a. Hominids (apes) 1. Homo a. Bipedal b. Enlarged cranial cavity / brain c. Reduced lower jaw d. Many species of homo coexist...
View Full Document

{[ snackBarMessage ]}

Page1 / 2

Lecture 17 - chordates II - IV The reptiles A Extant...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online