BZ471, Steam Biology & Ecology Exam 1

Transcription

1 BZ471, Exam1, p.1 BZ471, Steam Biology & Ecology Exam 1 Name Matching. Select the single best (most precise) answer for each of the following. Use each answer no more than once. No partial credit is given. E Term referring to the concentration of all dissolved major ions in water. K stream with multiple, unstable channels S Stream where sediment supply and mass > flow transport capacity U The deepest pathway along the longitudinal profile of a stream reach a) hardness b) plankton c) unconstrained d) meandering e) total dissolved solids f) seston g) meander length h) depositional i) pool j) wetted perimeter k) braided l) degrading m) alkalinity n) drag o) detritus p) wash load q) salinity r) thalweg s) aggrading t) Fine particulate organic matter u) Thalweg v) embedded w) anastomosing 1

2 BZ471, Exam1, p.2 Multiple Choice. Write the letter corresponding to the single best answer in the space provided. B Which of the following life cycle types are diapausing eggs necessarily required? a) Slow seasonal b) Fast seasonal c) Non-seasonal d) Synchronous e) Asynchronous B Which of the following is the correct order for increasing particle size according to the Wentworth scale? a) Sand Silt Gravel Cobble Boulder b) Silt Sand Gravel Cobble - Boulder c) Sand Silt Cobble Gravel Boulder d) Silt Sand Cobble Gravel Boulder e) None of the above are correct B Based purely on physical principles, under which of the following situations would the equilibrium O 2 concentration (mg/l) in water be the highest? a) Riffle in stream at high elevation at a water temperature of 5 C. b) Riffle in stream at low elevation at 5 C. c) Riffle in stream at low elevation at 25 C. d) Bottom of a pool in stream at low elevation at 5 C. e) Bottom of a pool in stream at high elevation at 25 C. B Streams are said to be buffered against acidification (e.g., from acid rain) when soil water from rain reacts with to produce, which reacts with stream water to produce to neutralize. a) CaCO 3, groundwater, OH -, H + b) CaCO 3, HCO 3 -, OH -, H + c) HCO 3-, groundwater, OH -, H + d) H 2 CO 3 -, CO 3-2, HCO 3 -, OH - e) None of the above True/False. Write the word True or False for each question in the space provided. True An increase in shear stress increases stream competence. False Aquatic insects in temperate streams enter a period of diapause and no growth over the winter period when water temperatures drop below 4 C. False The number of generations per year for all species of aquatic insects is fixed across its entire geographic range. 2

3 BZ471, Exam1, p.3 False The magnitude-frequency principle applied to sediment movement in streams argues that it is the most extreme event, occurring with low frequency, that transports the most suspended load over an annual cycle and thus is most important in maintaining the characteristic channel form of the stream. False The further north one goes in the Northern Hemisphere, the more one would expect to find stream insect communities comprised of mostly multivoltine species. Definitions. Provide the word whose definition is given. Bankfull Discharge Term for the flood that occurs about once every years in a stream (although the range can be once every 1 1 years) and is associated with maintaining the channel dimensions. Semi-voltine Meandering Complete adult. Name for the kind of aquatic insect that completes one generation in two years. Name for a channel morphology when sinuosity is greater than 1.5. Type of development that includes egg, larva, egg and Short Answer. Provide short answers to the following. (One to a few key words or concepts will usually suffice. Complete sentences not needed.) Why, according to Leopold (book chapter) is a meandering stream with alternating point bars and cutbanks in a state of dynamic equilibrium with respect to sediment transport and storage? As banks are eroded, bars are building, so that there is effectively a redistribution of the sediment in the alluvial river. The number of bars and cutbanks are roughly constant over time, but their locations are moving as the channel migrates across the floodplain. Why is the ph of normal rainwater about 5.6 rather 7. like distilled water? Atmospheric CO 2 is dissolved in Rainwater creating carbonic acid (H 2 CO 3 ), which dissociates into HCO 2 and H +. 3

4 BZ471, Exam1, p.4 Give two reasons why organism abundance and species richness (diversity) is generally lower in sand than in gravel. (1) more interstitial spaces in gravel (2) sand less stable during high flows Give 3 possible morphological adaptations of benthic macroinvertebrates to current velocity. (NOTE: Only your first 3 answers will be counted, so don't list more than 3.) see notes for lecture 5, table 5 2) 3) If the cross-sectional area of a stream is 8 m 2 and the discharge is 2 m 3 /sec, then what is the average velocity?.25 m/sec Which experiences a greater lift force as it moves across a smooth stone in a fast stream, a snail with a 1 high mm shell, or one with a 2 mm high shell? Explain why. 2 mm shell because flow will have to accelerate faster to get over the top of the 2mm shell and this will create a greater Umax Umin (see lecture notes) For the following stream network, Strahler stream order at point A = 3. Shreve link number at point A = 6. 4

5 2 15 BZ471, Exam1, p Days after Egg Hatch 36 Graphs and Interpretation. If an insect requires 38 degree-days > C to grow and attain developmental maturity to emerge, indicate the approximate day that emergence of the insect will occur for the hypothetical stream thermograph drawn below. Calculate the DD> for each block of the thermograph and add until you get to 38. Days -6 = 1*6 = 6 DD By day 12 = *6 = 15 By day 24 = *12 = 39 At day 235 = 39 5*2 = 38 Draw a figure that shows how water velocity (x-axis) changes with depth (y-axis) from the bottom of a stream to the surface. Explain the shape of the relationship and indicate the one point on the line where the average velocity occurs. See class notes for lecture 2 (Fig. 2.8) 5