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This lab report explores the characteristics of amniotes, a group of vertebrates that includes reptiles, birds, and mammals. Various topics such as the development of amniotes, their traits, and the evolution of birds and mammals from reptilian ancestors. Students will learn about the differences between reptiles, birds, and mammals, their skeletal structures, and the similarities and differences among them.
Typology: Lab Reports
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Lab day and time: ____________ Name ________________________
The vertebrates we will study this week are all amniotes. That is, amniotic vertebrates all surround the developing embryo with layers of membranes ( amnion surrounds the embryo, the allantois collects wastes, the yolk sac contains nutrients, and the chorion protects all the other membranes and embryo); sometimes an additional layer is added, a hard, waterproof shell. A second trait that has evolved in some amniotes is endothermy. Mammals and birds, and few reptiles, are endothermic, keeping their body temperatures relatively constant. This strategy is costly; mammals and birds have metabolic rates (consumption of Oxygen) that are 7 to 10 times that of a reptile. To keep their internal body temperatures constant requires a great deal of energy to meet these high metabolic demands. Many ectothermic reptiles, on the other hand, can go without food for long periods of time, given their low demands for consuming Oxygen.
Video segment: Shape of Life-bones, brawn and brains What evidence is the video saying supports that dinosaur bone grew relatively fast? How would the graduate student know what patterns to look for in the bone to indicate fast growth? In other words, how could she know that the organization of bone that she sees provides her with an answer to growth rate of dinosaurs? Which hypothesis is suggested for the demise of the dinosaurs? Video: The Reptiles What types of behaviors attract a crocodile hunting response? What are the two parts that make up the turtle shell, and from which skeletal parts are they derived?
What are the three types of turtles and what is the basis for these groupings? Describe the ways in which snakes are able to move? What sensory system do snakes use to hunt that we do not have? Video: Life of Mammals—a winning design What characteristics define the group of vertebrates called mammals? Which living mammals are considered the most closely related to the common ancestor to all mammals? How are these mammals connected to reptiles? How do marsupial mammals like kangaroos give birth and care for their young? How do placental mammals care for their young during early development? Video: Life of Birds—to fly or not to fly How is the fossil Archaeopteryx like a reptile and how is it like a bird?
Aves The birds are easily identified by their possessing feathers (though some feathers may look more like hair). Look at a feather under a dissecting scope or microscope. Observe the pigeon skeleton and representatives of birds that are located around the lab. Make notes and sketches below. Mammals The mammals all have hair and females have mammary glands for nursing young. Observe the mammals skeletons and representatives that are available. Make notes and sketches below.
If birds and mammals evolved from a reptilian ancestor, then there should be similarities among the three groups (note that I am not saying that birds and mammals evolved from the same reptilian ancestor). Can you find any similarities among the alligator, cat and pigeon skeletons? If you do then, of course, tell me what these similarities are. Look at the pigeon and bat skeletons. Based on the structure of the bones making up the wing, would you consider these structures to be homologous (i.e. did the wing evolve first prior to birds diverging (separating) from bats or did birds and bats evolve their wings after these two groups separated? Make sure and back up your answer with evidence.