Do Amphibians Have Amniotic Eggs

Review Questions for Honors 301T

HOL Ch. 9: Amphibians and Reptiles

ane. Most people think of vertebrates in terms of a conceptual progression:

lobe-fin fish -> amphibian -> reptile -> mammal or reptile ->bird

Cladistic classifications recognize but monophyletic taxa (i.eastward., "Rule of Monophyly"):

The lobe-fin fish clade (Sarcopterygii) includes a tetrapod subgroup (Tetrapoda), which likewise has subgroups Lissamphibia (frogs, salamanders, etc.) and Amniota (reptiles including birds plus mammals).

This requires some adustments in thinking.

The fish closest to state vertebrates are "lobe fin fishes" suh as coelacanths, lungfishes, and early on aquatic members of the clade, Ostieolepiformes, such as Osteolepis (review figures on pp. 91, 93, and 103). Tetrapods are also members of Ostieolepiformes. The primeval tetrapods* were aquatic, including Acanthostega (see Fig. 8.fifteen, p. 111). Notation that the earliest tetrapods were quite large animals. Except for their aquatic reproduction, they would probably take resembled big lizards or crocodiles (see p. more salamanders. Salamanders, frogs, and other living "amphibians" are in a quite derived lineage of tetrapods, called Lissamphibia. Reptiles and mammals are members of a grouping called Amniota (the amniotes). Amniotes have an amniotic egg, which typically has a difficult covering to forestall desiccation. In contrast to a typical frog male, which clasps a female frog and externally fertilizes her eggs as they are spawned, an amniote male needs to copulate with a female in gild to fertilize her eggs earlier they are internally encased in an egg shell and laid externally.

I remember it is important to learn to speak of tetrapods, which in plow are divided into sub groups. I adopt this approach to speaking of early amphibians that later "evolved into" reptiles, which later "evolved into" mammals, while other reptiles "evolved into" birds. This change in speaking has subtle impacts on how ane thinks almost the relationships among living terrestrial vertebrates. Information technology is true that early tetrapods (like "fishes") were clearly "amphibians" in terms of their dependence on aquatic habitats for reproduction merely, every bit Dr. Cowen points out, most of these early tetrapods more closely resembled lizards or crocodiles (run across p. 108) in their advent and life mode than they did salamanders or frogs. One problem is, the novelty that clearly unites living members of the amniote clade (reptiles + mammals), the amnion, is a soft role feature that is not preserved in the Paleozoic tetrapods. The amnion is conspicuously associated with terrestrial, not amphibious, reproduction, but nosotros are not really sure when it evolved. This is because most of these early tetrapod lineages are extinct.

Dr. Cowen likes to put specific fossil taxa direct on the branches of his "phylograms." I prefer to describe "cladograms" with all taxa (fossil and living) at the tips of the cladogram. Here is an example of how I would redraw Cowen'south phylogram of tetrapods (Fig. 9.two, p. 114):

------------------------------

So the question here is, tin can you organize the following tetrapods into a cladogram based on the cloth presented in Ch. 9?

At that place volition about certainly be a question on the next quiz that depend on your ability to "clade think" in this way. The tetrapods are:

Living: salamander, frog, cadger; Extinct: Ichthyostega, the temnopondyl Cacops, the anthracosaurs, Diplocaulus and Seymouria. Combine all of these into a single cladogram.

Extra challenge #one: add microsaurs and Westlothiana ("Lizzie").

Extra challenge #2: specify novelties that provide evidence for the basal (lower) nodes on your cladogram. This spider web link on Seymouriamorpha may help hither, because Dr. Cowen does non really get into the technical details of skeletal novelties used past paleontologists.

two. What were likely habitats for early reptiles?

three. How is the amniote egg analogous to a infinite transport? How does the contrast between the amphibious eggs of frogs and salamanders, and the amniote eggs of lizards, affect the mode of fertilization?

four. According to Dr. Cowen, why were about early terrestrial vertebrates and arthropods predators, rather than herbivores, when and so much establish material was bachelor? What does this have to exercise with symbiosis in animals?

5. What is an instance of a large Paleozoic insect? How large did they get?

*Most specialists at present adopt to ascertain Tetrapoda as a "crown group": in this case the terminal common ancestor of living lissamphibians and amniotes, and all of its descendants (i.east., the tetrapod "crown grouping"). They would normally refer to the more inclusive clade, that as well includes Acanthostega, Ichthyostega, and Tulerpeton (i.e. "stem tetrapods") every bit Tetrapodomorpha. As of the Fifth edition of our text, Cowen appears to have partly changed to this view, and refers to the near basal "stem grouping" fossils as tetrapodomorphs. Cowen now includes inside the tetrapodomorphs the recently discovered Kenichthys (see p. 105) from Cathay (395 MY), which lacked limbs only did have choana, or internal nostrils. These are a cardinal feature of tetrapods (see Abstract for Zhu and Alberg, 2004). Yet, he still does use what he calls a "stem" definition of Tetrapoda, calling any species that have feet, not but fins, a tetrapod.

[Go to Previous: Review Questions for HOL Chapter 8]

[Go to Adjacent: Review Questions for HOL Chapter 10]

[Go to History of Life listing for Chapter 9]

[Return to Honors 301T Habitation Page]