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Assignments

Your course grades will be based on the total number of points that you accumulate by doing the assignments listed in the table below.

WEEKLY TREE QUIZZES (6 @ 6points; 36 pts)

During each Arboretum laboratory there will be a 6 point quiz in which you will be asked to 1) identify 2-3 tree species and their characteristics, and 2) provide term or definition to plant structures from vocabulary list below.

These terms should become a part of your working vocabulary. Definitions and illustrations can be found on the Vocabulary webpage and in the "Basic Features of Trees" section (pps. 13-17) of your Trees of North America textbook.

LABORATORY FINAL (20 pts)

The laboratory final exam will be held on the UW campus. You will be asked to provide the scientific OR common name of 20 species. These trees are not identified as part of the UW Campus Tree Tour. Practicing your tree identification on the Brockman tree guide is an excellent way to prepare for the exam. 

REPORT ON PLANT ADAPTATION (15 pts)

The scientific literature is the main means of conveying and archiving ideas about how the natural world works. There are two major types of papers: 1) "data" papers, which present new information on a topic, and 2) "synthesis" papers, which discuss the implications of the findings from diverse data papers. You are to select of of the data papers below, which represent one steps taken to increase understanding of some type of tree adaptation. You will work in groups of 3 students, and present your assessment of the paper as a 12 minute powerpoint presentation.. Take a look at the papers and rank them according to your preference (1 = first, 6 = last). Electronically submit your ranking by April 7. I will make up groups to accommodate your choices, giving preference to people who submit choices early.ss

1. The fitness consequences of bearing domatia and having the right ant partner: experiments with protective and non-protective ants in a semi-myrmecophyte
2. Enhanced resistance to fungal pathogens in forest trees by genetic
transformation of black spruce and hybrid poplar with a Trichoderma
harzianum endochitinase gene
3. Tracheid diameter is the key trait determining the extent of freezing induced
embolism in conifers
4. Phloem Loading: How Leaves Gain Their Independence
5. Seedling growth in conifers and angiosperms: impacts of contrasting xylem structure
6. Facing herbivory as you grow up: the ontogeny of resistance in plants

On May 17 and 19, groups will present a powerpoint discussion, summarizing:

1. The main question
2. The motivation for the question (why is it interesting)
3. The authors (their positions and pictures)
4. Examples that illustrate one or two interesting elements of the paper AND are related to topics/species from class (or PNW in general).

WRITTEN EXAMS (2 midterms = 30 pts each; final = 48 pts)

The midterms cover material from both lecture and laboratories for periods between exams (or beginning of quarter). The final exam is comprehensive, covering lecture and laboratory material for the entire quarter.

Example (1st Exam 1997, correct answers are in parentheses):

1. (4 pts) Give the scientific name of the following species:

a. leaves in fascicles of 5, 2-4" long; cone 8-10" long, with rounded unarmed cone scales. (Pinus monticola)

b. leaves linear, sessile, several-ranked, 4-stomatal bands; cruciform buds; cones with exserted bracts: shatter when mature. (Abies procera)

c. leaves linear, petiolate, lemon aroma; lanceolate buds; cones with 3-pronged exserted bracts; thick, furrowed bark. (Pseudotsuga menziesii)

d. leaves scale-like, or awl-shaped; branchlets not flattened; round cones with fused scales, succulent, glaucous. (Juniperus sp.)

2. (6 pts) Describe 2 characteristics that distinguish between the following groups. Describe the condition of each characteristic in each group. YOU FILL IN THE FOLLOWING 3 TABLES: (NOTE: there are other correct answers than those below)

Characteristic	Tsuga mertensiana	Tsuga heterophylla
1 (cones)	(2-3 inches long)	(~ 1 inch long)
2 (leaves)	(several ranked)	(2-ranked)

Characteristic	Calocedrus	Chamaecyparis
1 (cones)	(2 large cone scales, oblong)	(>2 cone scales, round)
2 (leaves)	(whorled)	(decussate)

Characteristic	Larix	Cedrus
1 (cones)	(do not shatter when mature)	(shatter when mature)
2 (leaves)	(deciduous)	(persistent)

3. (2 pts) Give the common name of a species having the following traits: (Other correct answers are possible)

a. leathery cone: (mountain hemlock)

b. 2 needles per fascicle: (lodgepole pine)

c. scale-like leaves: (western redcedar)

d. very flexible branches: (Alaska yellow cedar)

4. (1 pt) Define the following terms:

a. whorled: (more than 2 leaves at each node)

b. pubescent: (with fine hairs)

5. (3 pts) There is often more than one type of adaptation to a given environmental condition. Choose ONE of the following examples to explain.

a. Name 2 species that are well adapted to fire, but have features that make them successful in different types of fire. Describe the adaptations to fire in each.

Species1: Ponderosa pine: thick bark is adaptation to low intensity fire

Species2: Lodgepole pine: closed cones are adaptation to high intensity fires.

OR

b. Name 2 species that are well adapted high snow fall, but differ in the features that make them successful under such conditions. Describe the adaptations to snow in each species:

Species1: Alaska yellow cedar: flexible branches shed snow

Species2: Subalpine fir: very short branches avoid large accumulations of snow

6. (1 pt) What is meant by binomial nomenclature? Species name has 2 words (genus name plus adjective)

7. (2 pts) Most people think that geographic races are precursors to future species. Why? Discuss role of geographic isolation as a reproductive barrier that leads to the formation of new species.

8. (3 pts) Because adult trees have hundreds or thousands of buds, trees could be full of branches growing in all directions. Why aren't they? Explain your reasoning. Discuss concepts of "coordination of parts" (i.e. role of hormones) and emphasize the importance of crown geometry (ie pattern of all branches) as a general feature of trees.

9. (2 pts) The vascular cambium is a special adaptation found only in trees. What features of trees result from the presence of a vascular cambium? Explain your reasoning. Discuss role of cambium in making large form of trees.

10 (4 pts) You boast to a friend that you can make numerous accurate predictions about the characteristics of trees on a site by knowing the climate of the location or the length of time since the last major disturbance. Make 2 predictions about tree characteristics for EACH situation below and explain your logic.

QUARTER PROJECT  (30 pts)

OBSERVATIONS AND HYPOTHESES

Introduction:

The human experience is largely devoted to acquiring knowledge--directly through daily experience and indirectly through formal education. In either case, knowledge ultimately results from the process of making observations and trying to guess the causes of observed phenomena. The scientific method is simply a formalization of this process. Guesses to explain an observed condition are called hypotheses. To determine whether a given hypothesis is correct, more information must be collected. If additional data are not contradictory, the original hypothesis is supported but not proven to be true (as it is possible that new data may be contradictory). Thus, we believe something is true because we cannot find evidence to contradict our current understanding of it. In scientific terms--acquiring knowledge proceeds by attempts to disprove hypotheses.  The intent of the quarter project is to involve you in the process of formulating and testing hypotheses. The first and possibly most important step is to make an observation of general consequences, as it is more important to understand a repeated phenomenon than to explain a freak occurrence. The major emphasis of this exercise is, therefore, on gathering data to document a general condition. The secondary goal is to propose an explanation that can be tested by the collection of additional data.  

Specific Requirements:  

1. Observe a vegetative, reproductive, or ecological condition of a tree or shrub species at three different locations (specify each location).
2. Document the observed condition using sketches, photographs or measurements.
3. Propose a hypothesis to explain your observation (explanatory hypothesis, see below).
4. Describe additional data that should be collected to disprove your hypothesis.  

Format of Report:  

Your report should address the four parts identified above. The text should be typewritten, any illustrations carefully prepared, and sources referenced. Four to five pages will suffice--no bonus for extra long reports. They will be evaluated on the basis of the following criteria:

• quality of original observation (7 pts)
• adequacy of documentation (8 pts)
• critical thought (8 pts)
• clarity of expression (4 pts)
• neatness of presentation (3 pts)  

Time Table:

Apr 19: Report group membership on line
Apr 26: Submit preliminary description of observation on line (one paragraph, ungraded)
May 10: Deadline for having project outline approved by instructor on line (ungraded)
May 26: Submit a 4-5 page report NOT ON LINE (graded)    

Comments for Conducting Project and Preparing Report

1. Observations: Keep your eyes open as you walk around campus and the Arboretum. You might look for interesting vegetative or reproductive structures, changes in structures related to their position in the tree (for instance, height from ground or distance from stem), or changes in structures depending on the location or age of the tree. Once you have spotted two or three different phenomena, keep checking them at other locations, preferably under natural conditions. One or two of them may be worthy of further pursuit. Being observant and perceptive is the key to most discoveries. For example, you may notice that a certain pin oak tree near the Hub has mature leaves that are quite variable in size and shape. Some leaves have large blades and shallow sinuses (indentations between lobes), while other leaves have smaller blades with much deeper sinuses (i.e., they are more deeply dissected). In order to confirm your observation, you check several other pin oaks (two in the Arboretum, one in a residential neighborhood), and find that they, too, have variable leaves. Further examination reveals that the deeply dissected leaves are typically found in the periphery of the crown, the more entire leaves in the center and at the base of the tree.

2. Documentation: Observations must be documented in order to be communicated and verified by others. The simplest and often most effective documentation is the collection and preservation of appropriate specimens. Plants lend themselves well to this approach. Photos and drawing are good substitutes. However, none of these methods are suitable for dealing with large numbers for quantitative evaluation and/or long-term storage. Thus, the observation is typically translated to the language of numbers and expressed in quantitative statements. In our pin oak example, you would collect a few leaf specimens and press and dry them. You might measure the deepest (or shallowest) sinus in peripheral vs. central leaves. You might then decide to express sinus depth as a percent of total leaf length for each of several leaves. However, it may also be that your leaves don't fall into neat categories but vary depending on crown position. You might then compare leaves from different "shells" of the crown (e.g., at radius r = 0.25, 0.5, 0.75 and 1). You would also give exact locations of your specimen trees (e.g., a map) and a brief description of their immediate surroundings (e.g., neighboring trees).

3. Hypothesis: The formulation of testable hypotheses is perhaps the most critical step in the scientific process. It converts a hunch or observation into a proposition that can be subjected to systematic examination. The hypothesis need not contain a profound truth nor does it have to spell out all conditions in order to be useful. We should view hypotheses as practical working tools (therefore the often used term "working hypothesis"), which take us step by step through an iterative process of elucidating a particular phenomenon.  (Each hypothesis has its corresponding counter-statement, or Null Hypothesis, which is easier to disprove the Null Hypothesis. We will not deal with Null Hypotheses in this exercise.)  It is useful to distinguish descriptive and explanatory hypotheses, the former serving to test the generality of a condition, the latter aiming at elucidation of its causes. In our example, the descriptive hypothesis might be stated as follows: In pin oak, mature leaves from the periphery of the crown are more deeply dissected than mature leaves from other crown positions. Note that the descriptive hypothesis, as stated, does not explain the phenomenon; it is merely a formal statement that your observation is always true and sets the stage for an eventual explanation by making the observation testable. Anybody can now collect data and decide whether the descriptive hypothesis is to be accepted or rejected. If rejected, the hypothesis would have to be modified and might then be proven acceptable.  The explanatory hypothesis states a possible cause for the pattern stated in the descriptive hypothesis. In our example it may be stated: "Peripheral leaves in pin oak are more deeply dissected to reduce overheating and excessive water loss." This hypothesis suggests that leaf variation in pin oak reflects an adaptive strategy to minimize water use; since peripheral leaves are exposed to higher light intensity and temperature, they adjust their morphology to minimize heat impact. The tree would benefit from this because it would require less water for transpirational cooling to be pumped to peripheral leaves.

4. A test that can judge the merit of an hypthesis: Modifications in the formulation of the hypothesis are often necessary to make t amenable to falsification.  The purpose of this part of the exercise is for you to develop a concrete idea on how to collect data to test your explanatory hypothesis, although you will not actually collect the data. Thus, you should briefly describe several ways in which data could be collected for this purpose. In our pin oak example, several tests suggest themselves:

1. Measure leaf temperatures on sunny days in peripheral leaves and more central leaves; contrast these data with those collected on overcast days.
2. In a similar way, measure water use by individual leaves of the two types.
3. Experimentally remove the peripheral leaves in part of the crown and expose the less dissected leaves to high light and temperature. Take the same measurements as in (1) and (2) and contrast them with data taken on peripheral leaves in a control (undisturbed) portion of the crown.
4. Compare the degree of leaf dissection in natural seedlings or saplings growing (a) out in the open and (b) under a forest canopy.
5. Experimentally raise seedlings from the same seed lot under (a) high, (b) low light intensity and combine this, in a factorial design, with a high and low water regime.   You may ask yourself which of these tests most directly addresses the hypothesis and what you would consider sufficient data to reject the hypothesis.  

PAST PROJECT TOPICS

MISCELLANEOUS

• Hedera: leaf size and shape variation- ground versus tree trunk
• Juniperus chinensis: distribution of juvenile vs adult foliage
• Picea sitchensis: drooping leader related to growth rates
• Sequoiadendron giganteum: lack of variation
• Picea sitchensis: leaf size versus bark thickness

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