BIO 112: Principles of Biology II
Review 2 KEY

Spring 2002

For each question or part to a question, limit your answers to the space below each question, unless otherwise specified.  Any part of your answer outside of the space provided will not be graded.

1.      Address one of the following as it relates to protists and eukaryotes (10 pts):

a.       Outline the evolutionary history of organisms classified as protists, especially as it relates to other major groups of organisms.  Explain in your outline how protists, as a group of organisms classified in a Kingdom, can either be considered polyphyletic or paraphyletic, but not monophyletic.

The ancestral eukaryote lead to protists, but also to plants, animals, and fungi. Protists are a mixed bag and are defined somewhat by what they're not. They have no one common ancestor that is not shared with other Kingdoms. Therefore, they are not monophyletic. They are polyphyletic if one considers the different groups of protists, such as the ciliates or the algae. However, they can be considered paraphyletic if one considers the ancestor of all eukaryotes. Interestingly, no one chose to answer this question!

b.      Outline the endosymbiotic theory of the evolution of eukaryotes.  Include at least one other evolutionary event that may have facilitated endosymbiosis, and two pieces of evidence that support the endosymbiotic theory.

Evolution via endosymbiosis involved either incorporation of prokaryote prey or an external symbiont that became internally symbiotic. It was ingested, but not digested, and this event may have occurred at least three times, leading to Peroxisomes, Mitochondria & Chloroplasts. The events may have occurred between an anaerobic phagocytotic eukaryote and aerobic prokaryote, or between two prokaryotes, but either way, it had to have been mutually beneficial, the endosymbiont must survive and reproduce in host, the symbiont must lose ability to survive out of host, and the host cannot survive without symbiont. Evidence for endosymbiosis includes genetic material of mitochondria and chloroplasts, as well as their prokaryote-like ribosomes. mtDNA are monophyletic, and some sequences closely related to extant bacteria, antibiotics affect mitochondria and chloroplasts. Other events that may have facilitated the events include the evolution of oxygen in the atmosphere - this will increase benefit of anaerobic host having an internal symbiont that can deal with oxygen - and the loss of the bacterial cell wall, which increased infolding and size of evolving eukaryote.

2.      List three of the benefits of the presence of earthworms in terrestrial ecosystems (6 pts).

Soil aeration, breakdown of detritus, release and movement of soil nutrients, soil drainage, soil formation, movement of organic matter.

3.      Compare and contrast the body plans of animals in the phyla Annelida and Chelicerata.  Give one example of the adaptive value of that body plan to a representative animal in each phylum (10 pts).

Both have a coelom (although it's reduced in Chelicerata), both are segmented, both have bilateral symmetry. Annelids have a hydrostatic skeleton for support, which is adaptive for earthworms that burrow in the soil - they have independent control of each segment and can stretch or contract different body regions at the same time. Chelicerata have 4 pairs of walking legs and an exoskeleton, as well as highly modified mouthparts (which vary from taxa to taxa). The adaptive value of the exoskeleton for scorpions is obvious - it prevents desiccation and provides protection from predators.

4.      Briefly outline the general mating habits of either spiders or scorpions.  Briefly explain the adaptive value of complex courtship rituals (8 pts).

Spiders: males must signal to females that he is a potential mate. In web-building species males will often pluck the web of the female in a species-specific pattern. For actively hunting species males will often pounce on females and then begin a courtship dance, or series of behaviors that cue the female to recognize the male as a mate. Often, the female must respond with cues of her own so that the male can determine that he's not made a mistake. After courtship, males eject a packet of sperm and use their modified pedipalp to insert it in the female.

Scorpions: again, males must signal to females that he is a potential mate. After the signal, the pair join pedipalps and begin a courtship dance during which the male will release a packet of sperm on a stalk. He then positions the female over the stalk and she draws it into her spermathecae (storage receptacle).

The adaptive value is that predators such as these must recognize members of the opposite sex as potential mates and not potential threats or prey.

5.      List two advances in the course of vertebrate evolution that specifically allowed colonization of terrestrial habitats (4 pts).

Shelled egg, lungs, cuticle/waterproof skin, legs from fins

6.      Briefly explain the concepts of negative and positive feedback.  Give one example of each from vertebrate physiology (10 pts).

Feedback information can either reduce/reverse a process, or amplify it, depending on whether it is negative or positive feedback. Negative feedback maintains a particular parameter or value close to a set point, while positive feedback takes the value away from the set point. Negative feedback thus maintains homeostasis, and is usually used to bring a positive feedback response back to a set point after the signal amplification is completed. Examples of negative feedback abound in all the systems we've studied. Positive feedback examples include sexual arousal and emptying body cavities.

7.      Explain the mechanism that allows a fish to have the same metabolic rate in the summer, when water temperatures average 24^oC, as they do in the winter, with temperatures on the order of 4^oC.  Be specific (8 pts).

I was looking for the concept of acclimitization. This is where ectotherms will have two sets of enzymes (isozymes) that have different temperature optima. This allows them to maintain a steady metabolic rate even though their body temperature changes. I also accepted the example of the "hot" fish, where it maintains a less variable body temperature by using countercurrent heat exchange in its core blood circulation. Heat is retained in the core of the fish.

8.      How do animals regulate body temperatures with blood flow?  Answer this question using two specific examples, one of an ectotherm and one of an endotherm, each of which employs a different mechanism (10 pts).

Ectotherms: can change heart rate, and consequently, blood flow to the extremities, depending on the external temperature. This may be in conjunction with behavioral regulation, but behavioral regulation alone is not sufficient to answer the question.

Endotherms:

9.      The three organ systems that deal with respiration, nutrition, and circulation are closely tied together.  Provide two examples, in one sentence each, of how control and regulatory mechanisms of one system affects at least one of the other two systems.  Be specific (8 pts).

10.  Select one of the following animals and describe how two adaptations of the respiratory system increase Q in Fick’s law of diffusion. Be SPECIFIC (8 pts).

a.      Fish: countercurrent exchange in gills, short diffusion distance, filaments and lamellae increase surface area

b.      Insect: tracheoles keep oxygen in air (higher coefficient of diffusion than in water), short diffusion distance, much surface area at ends of tracheoles             

c.      Mammal: huge surface area with alveoli, short diffusion distance, perfusion keeps concentration gradient somewhat high, air breather                

11.  Discuss one of the following as it relates to mammals (10 pts):

a.       How do the endocrine system (hormones) and the circulatory system help maintain homeostasis in the excretory system? Be specific and use at least two examples.

b.      List two problems of being an herbivore, and discuss specific adaptations herbivores have evolved to overcome those problems.

12.  While out hiking along the Oregon coast, I discovered a species of shrimp living in a tide pool.  List two conditions that are likely to change over time in this tide pool, and list one problem that each change presents for one physiological system in our creature (one problem in each of two systems) (6 pts)?

13.  Apply the concept of countercurrent exchange to two of the following three systems.  For each: 1) identify the specific matter or energy that is exchanged, 2) how the countercurrent exchange helps maintain homeostasis, and 3) which physiological systems are involved (12 pts):

a.       Camel’s nasal passages

b.      Bony fish gill: Exchanges oxygen and carbon dioxide (and ammonia). Involves or is part of circulatory, respiratory, and excretory systems. Countercurrent exchange is primarily used in gas exchange, and not so much for ammonia excretion, and having water flow opposite to blood flow, gills are much more efficient than concurrent flow and can extract a much higher percentage of oxygen and get rid of more carbon dioxide.

c.       Nephron in a Mammalian kidney: Exchanges solutes (retains some, excretes others), retains water. Involves the circulatory and excretory systems, and the nephron acts as a countercurrent multiplier, ultimately pulling more water out of the filtrate and concentrating the urine 2-12x plasma concentrations.

14.  Discuss the integration of up to four (4) systems that we’ve studied (besides the reproductive system) and how they specifically affect blood glucose levels or are affected by inability to maintain proper blood glucose levels.  Use only one sentence for each example (>1 example can come from the same system).  Each example will be worth 10 points divided by the total number of examples you use (e.g., if you choose 2 examples, they will be worth 5 points each; 4 will be worth 2.5 each).  Use the back if you wish to continue your list.

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