Science Homework Help

Assignment #1

Review Chapter 18: Evolution and the Fossil Record and answer the following questions in a single document that you will upload using the link below. https://b-ok.cc/book/2470416/fcb216

Question 1. Consider the following types of fossils:

• • marine-dwelling forms
  • burrowing species
  • pollen grains
  • skeletal elements from sharks and rays
  • flowers

For each one, list whether you would expect them to be common or rare in the fossil record, and what aspects or characteristics they have that make them so (hint: think about (a) the types of structures that make up their forms and (b) the environment that they live in, and how each these might play a role in the probability of their fossilization).

Question 2. Trace fossils record the behavior of ancient organisms, but not necessarily their form; it is often difficult or impossible to link a given trace fossil with the precise species that made it. Nonetheless, trace fossils provide valuable data for reconstructing the history of life. Your textbook mentions that dinosaur trackways can be used to estimate living dinosaurs’ speed. Generate another way in which trace fossils could contribute to paleontological studies even if the identities of their makers are unclear.

Question 3. Suppose that a species first appears in the fossil record 350 mya. Why is it logical to argue that this species actually existed before this date?

Question 4. Most fossils of Mesozoic birds are from marine diving birds. Relatively few terrestrial species are known. Does this mean that most Mesozoic birds were, in fact, marine diving birds? Explain your reasoning.

Question 5. One of the (many) mysteries of the K–Pg extinction is the different fate of ammonites and nautiloids. These were mollusks with buoyant, chambered shells that lived in open-water habitats. Ammonites went extinct during the K–Pg extinction, but some nautiloids survived. The two groups had different reproductive strategies. Ammonites are thought to have produced many free-swimming young each year that fed near the ocean surface and grew rapidly. In contrast, a female nautilus produces just a few large eggs each year, each of which rests quietly in the depths for up to a year before hatching into a small, slow-growing nautilus. Based on these different reproductive strategies, suggest a possible hypothesis for why the nautiloids, but not the ammonites, might have been able to survive an asteroid impact.

Question 6. Suppose you are talking to a friend about extinctions, and you mention that humans are known to have caused thousands of extinctions in the last few millennia. Your friend responds, “So? Extinction is natural. Species have always gone extinct. So it’s really not something we need to worry about.” Is your friend correct that extinction is natural? Is the current rate of extinction typical? Is your friend correct that if extinctions are natural, then they are not a problem for the dominant life-forms on Earth?

Assignment #2

Be sure that you have read the following articles.

• Callaway, E. 2015. ‘Dino-chickens’ reveal how the beak was born. (Links to an external site.) Nature News, doi: 10.1038/nature.2015.17507 [PDFActions]
• Singer, E. 2015. How dinosaurs shrank and became birds. (Links to an external site.) Quanta Magazine, June 2, 2015 [PDF
• Actions]

After reading the articles above, discuss the following topics in small groups and/or with your TA. You will be turning in your answers to the general questions at the end of the activity. You will need to submit your answers in a single document using the link at the bottom of the page. provided the pdfs

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Callaway (2015) Discussion:

• What prior knowledge (preliminary research findings) spurred the principal investigators (Bhullar and colleagues) to do this experimental study with the jaw development of chicken embryos?
• What did Bhullar et al. do in their experiment with chickens, and what did they find?
• What is the principal implication of the experiment’s results?
• What future research directions by the principal investigators of this study might be possible based on their findings?
• What future research directions by other scientists might be possible based on this study?

Singer (2015) Discussion:

• What is the basic premise behind the “hopeful monsters” hypothesis?
• What were the principal findings of the research on the immediate ancestors of extant birds by Brusatte?
• What were the principal findings of the research on body size evolution in dinosaurs by Benton and colleagues?
• What role did miniaturization play in the evolution of birds?

General Discussion Questions (for submission): Paedomorphism is often characterized as the retainment of juvenile characteristics in adults. For example, some salamanders such as the Mexican axolotl possess gills as adults, whereas gills are lost during the transition from larvae to adults in other amphibians. How might paedomorphism have played a role in the evolution of birds? Bhullar and his colleagues did not hatch the modified chickens for “ethical reasons” (Singer article) and did not write that in their approved research protocol (Callaway article). Do you think that arresting the development right before hatching was sufficient for the team to achieve their research goals, or might they be missing something by not bringing the modified chicks to term? Do the independent research studies of Brusatte and Bhullar (described in the Callaway and Singer articles) support or refute the “hopeful monsters” hypothesis that evolution occurs in leaps and bounds? In what way(s)? Do you think that the findings from this line of research as described in the two articles indicate that birds are more closely related (in an evolutionary sense) to dinosaurs or crocodilians or lizards? Please explain. How do you imagine that the evolutionary process of natural selection may have operated to cause the separation of the two different lines of jaw development of birds versus other reptiles and mammals? (NOTE: This question is not answered explicitly in either paper that you read. Try to think of your own answer.)