Case Study 11. What does the data tell us about how this species might fare if salinity in coastal waters increases due to pollution or decreases due to the melting of the ice sheets?Case Study 22. What is the effect of salinity on the rates of photosynthesis versus respiration in Euglena gracilis as shown in Figure 2? What does the difference in the initial slopes of the curves in the left panel tell us?3. What does the data in Table 1 tell us about the effect of salinity on the alga? How do the changes in pigment amounts in the cells as reported in Table 1 relate to the data from Figure 2, especially the change in the slopes that you discussed above? Case Study 1: The researchers used Ulva lactuca in this study. This species is a multicellulargreen alga growing in coastal seawater. It was collected in June (2000) towards the end of thegrowing season. Following collection, the algae were quickly rinsed to remove sediment andinvertebrates and transported back to the laboratory in filtered seawater. To reduce the timebetween collection and the start of each experiment (less than 30 min), salinity treatments wereprepared prior to collection. The effect of changing salinity on net oxygen production wasmeasured. Four sample (containing algae) and two control (without algae) were set up for eachsalinity treatment. The algal thalli were fragmented into small pieces (~2.5 cm?), firmly pressedbetween two paper towels, weighed (FW = fresh weight), and introduced into the sample bottles.Between 0.02 and 0.04 g (FW) of algae was added to each sample bottle. The bottles were thenincubated outdoors under conditions similar to the collection site (200 umol m²s1 of shadedsunlight at 28°C) and mixed by inverting each bottle once every 10 min. All replicates were runsimultaneously and light varied less than 2 µmol m²s1 over the area where the bottles wereincubated and less than 10 umol m ?s1 over the course of the incubation. After 1 h, final oxygenconcentrations were measured and net oxygen production calculated (umol O2 g FW hl) aftercorrecting for the controls and normalizing to the amount of algal tissue enclosed.-1500B4003002001001922252831Salinity (psu)-6-33Change in Salinity (psu)Figure 1: Net oxygen production in the five salinity treatments. Bars are mean values +standard error (n = 4). Salinity at the collection site was 25 psu (practical salinity unit, equivalentto g/kg). The top x-axis indicates the salinity for each treatment and the bottom x-axis indicatesthe change in salinity imposed by each treatment relative to the ambient salinity of 25Letters denote treatments that are significantly different (Tukey's test, P<0.05).Net O, Production (µmol O, g' FW h) Case Study 2: The researchers used stock cultures of wild-type Euglena gracilis (a unicellular,freshwater alga). Cells were incubated in the dark in 1.2 mL of 0.1 M potassium phosphate (pH7.4), for determination of oxygen uptake. After approximately 50% of dissolved oxygen hadbeen consumed, a light stimulus was applied to the chamber for determination of oxygenproduction using a Clark-type oxygen electrode. An aliquot of 50 µL of cell suspension wasextracted with 80% acetone and the amounts of Chlorophylls a and b were determinedspectrophotometrically.8040a 20060305100402010020200250500800 10002505008001000Light intensity (umol quanta m-2 sLight intensity (umol quanta m-2 s-1Figure 2: Effect of photon flux density (light intensity) on the rate of oxygen production ofEuglena gracilis. The numbers shown on the right side of the graph represent the concentrationof NaCl (mM) added to the growth mediumNaCI). The cells were exposed to the indicated light intensities through density filters and therate of oxygen production was measured at 30°C after 2 cycles of respiration/photosynthesis (leftpanel). Thereafter, 10 µM DCMU was added and the rate of respiration was measured (rightpanel). The data shown represent the mean ± standard error of 3 different cultures assayed. Inthe right panel, a: P<0.05 (200 vs. 0 NaCl)= 0 NaCl, O = 100 mM NaCl, A = 200 mMTab. 1. Effect of high salt concentrations in the growth medium on the chlorophyll content of light-grown Euglena cells. Growth, harvest-ing after 3 days of culturc, and chlorophyll determination were as described in Materials and methods. The results shown represent ug chlo-rophyll (10' cells)", mean + SD of 4 different experimental cultures. a, P<0.05 (vs zero NaCI)NaCl, mMTotal chlorophyllChlorophyll aChlorophyll bChl alb ratio83 + 1280 + 13128 + 10a15 + 515 + 228 + 9a69 + 710020066 + 14102 + 19a4.64.43.6PhotosynthesisGUiu 142,6 os 20 1owu)Respiration(nmol 0z 50 µg' chlmin'

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11th Edition

ISBN:9780134580999

Author:Elaine N. Marieb, Katja N. Hoehn

Publisher:Elaine N. Marieb, Katja N. Hoehn

Chapter1: The Human Body: An Orientation

Section: Chapter Questions

Problem 1RQ: The correct sequence of levels forming the structural hierarchy is A. (a) organ, organ system,...