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Lecture 14

BIO SCI 94 Lecture Notes - Lecture 14: Metabolic Waste, Eutheria, Reptile

Biological Sciences
Course Code
Robin Bush

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Chapter 35 Deuterostome Animals Part 2
In our class, we will assume that segmentation evolved multiple times
Pharyngeal gill slits
Dorsal hollow nerve cord
Muscular, post-anal tail
Vertebrae, Cranium
Jaws, then lungs and endoskeleton
Lobed fins act as primitive limbs
Coelacanths live deep in the sea. They stay down there. Lungfish can venture
onto land and breathe air for limited periods of time
The early vertebrate lineages look like “fish” and we refer to them casually as fish. On
the tree, they appear as a series of independent monophyletic groups that form a grade
Grade - sequence of lineages that are paraphyletic
1. Tetrapoda - limbs
2. Amniota - amniotic egg
3. Mammalia - lactation, fur
4. Reptilia - scales with hard keratin
Amphibians are tetrrapods, but they are a transitional group. Most live on land, but they
don’t have amniotic eggs and thus still need to lay their eggs in water
In many species, gas exchange occurs exclusively or in part through their moist,
mucus-covered skin
Tetrapods were the first vertebrates that could breed in terrestrial environments
Three major evolutionary innovations gave tetrapods this ability:
1. Amniotic egg
Only with the evolution of the amniotic egg did animals attain the
capacity to remain on land all the time
Amniotic egg keeps embryo from drying out. It provides food,
water gas exchange, and a toilet.
2. Placenta
3. Elaboration of parental care
Reptiles are well-adapted for terrestrial life because of three distinguishing features:
1. Scales, watertight skin
2. Well-developed lungs
3. Amniotic eggs
With exception of birds, all reptiles are ectothermic, meaning they they don’t use
internally generated heat to regulate their body temperature. Instead, reptiles
moderate their body temperature behaviorally.
Testudines - Turtles, tortoises
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