Cd++对草履虫种群的毒性作用

通过研究20℃培养条件下Cd 对草履虫(Paramecium caudatum)种群毒性影响,结果表明:Cd 对草履虫的24hLC50为0.3294mg/L,Cd 浓度对草履虫的种群增长率有极显著影响,多重比较结果显示高浓度组(0.25和0.30mg/L)下草履虫的种群增长率显著小于低浓度下(0.05、0.15和0.20mg/L)的值。回归分析结果表明草履虫种群增长率(Y,/d)与Cd 浓度(X,mg/L)之间呈曲线相关。在一定浓度范围内,草履虫种群增长率随Cd 浓度的升高而呈增大,但高的Cd 浓度显著地降低了草履虫的种群增长率;当Cd 浓度为0.1179mg/L时,草履虫种群有最大增长率1.5442/d。各浓度组与对照组之间的t-检验结果表明在较低的Cd 浓度范围内(0.05、0.10和0.15mg/L)草履虫的种群增长率显著大于对照组的值,而Cd 浓度为0.30mg/L时的草履虫种群增长率显著小于对照组的值。     

农药胁迫对草履虫个体生长和种群动态的影响

采用连续培养法探讨了草履虫(Paramecium caudatum)在甲胺磷、2,4-D丁酯和甲氰菊酯3种农药胁迫条件下的个体生长和种群动态,并利用Logistic种群增长模型对种群的增长曲线进行了分析.结果表明:甲胺磷和甲氰菊酯农药胁迫能改变草履虫细胞的大小和形态;不同农药不同浓度处理下,草履虫密度增长曲线均具有"S"型生长特点;农药胁迫下草履虫密度增长曲线符合Logistic模型(R2＞0.8),3种农药胁迫下K值明显降低;甲胺磷和甲氰菊酯农药胁迫下种群最大增长率低于2,4-D丁酯胁迫和对照.     

pH值对萼花臂尾轮虫种群增长及繁殖的影响

采用种群积累培养法,实验观察了 ｐＨ在３．５～１１．５之间（间隔 １）萼花臂尾轮虫 （Ｂｒａｃｈｉｏｎｕｓ ｃａｌｙｃｉｆｌｏｒｕｓ）种群的增长及繁殖．结果表明,该轮虫种群在ＰＨ６．５～８．５之间增 长较快, ８． ５时增长最快,即瞬时增长率 ｒ和种群密度较大和最大; ｐＨ在 ３． ５～４． ５和 ９． ５ ～１０． ５之间,种群为负增长,即 ｒ为负值; ｐＨ在 ５． ５～９． ５之间种群为正增长,即正为正 值．该轮虫存活的ｐＨ上限为１１．５,下限为３．５．在种群增长最适ｐＨ（８．５）条件下,该轮虫 的繁殖最快,即绝对带卵量最高（１３２个·ｍｌ－１）;ｐＨ在９．５时,其相对带卵量最高．为其它 ｐＨ值条件下的２～４倍．本研究结果可为淡水轮虫的大批量培养提供可靠的ｐＨ值技术指 标．     

培养温度和保存时间对草履虫密度的影响

草履虫是原生动物门纤毛纲的代表动物。在培养与保存草履虫的过程中,培养液中草履虫密度高低,直接影响学生的实验效果。实验证明,草履虫的生长、繁殖受温度影响比较大。草履虫培养液在不同温度条件下、保存时间长短不同,草履虫的密度不同。围绕着这一问题,进行了温度和时间对草履虫密度影响的研究。     

大丰自然保护区麋鹿种群增长模型以及种群密度对种群增长影响的研究

创建了一个关于大丰自然保护区半散养麋鹿种群增长的Logistic模型,该模型准确地预测了麋鹿种群的增长规律.作者通过对比和分析相关数据揭示了种群密度对糜鹿种群增长的影响并给出两个导致种群增长发生改变的临界值.     

温度对水螅种群增长和个体大小的影响

应用群体累积培养法,以枝角类为食物,在10℃、20℃和30℃三种温度下,研究了温度对水螅(Hydra sp．)种群密度、种群增长率和个体大小的影响。结果表明温度对水螅种群密度和个体体积由极显著影响。在培养初期,30℃下的水螅种群密度最大;而在培养后期,20℃下的水螅种群密度则显著大于30℃下的值;10℃下的值则始终最小。在同一温度下,种群增长率均与时间呈曲线相关,10℃、20℃、30℃的回归方程分别为：Y=0．000433X^2-0．00262X 0．00332、Y=-0．003367X^2 0．068335X-0．066489、Y=-0．018469X^2 0．188952X-0．030933。在研究范围内,30℃的水螅个体最小。     

食物浓度对方形臂尾轮虫发育历期与实验种群增长参数的影响

为探讨富营养化水体中大量发生的轮虫与微藻之间的关系 ,在实验室条件下 ,观测了不同藻类食物浓度下方形臂尾轮虫生命周期中各发育阶段的历时以及种群增长参数的变化。实验选用蛋白核小球藻为食物 ,浓度梯度为 0 1× 10 6、 0 5× 10 6、 1 0× 10 6、 2 0× 10 6、 4 0× 10 6、 8 0× 10 6、 12× 10 6cells/ml。结果表明 :食物浓度对方形臂尾轮虫的胚胎发育时间与繁殖前期历时、产卵量、世代净生殖率、世代时间和种群的内禀增长率均有明显影响。在食物浓度为 2 0× 10 6cells/ml时 ,方形臂尾轮虫的繁殖前期最短 ,产卵量最大 ,世代净生殖率和种群增长率最高 ,世代时间最短。方形臂尾轮虫可在高于其最适食物浓度的较宽的食物浓度范围内 ,保持较高的种群增长率 ,表现出较强的对环境中高浓度藻类的适应     

温湿度对松毛虫赤眼蜂种群增长的影响

在13—33℃、35％—95％R.H.范围内的7个恒温、13个温湿度组合下,测定了松毛虫赤眼蜂(Trichogramma dendrolimi Matsumura)的发育、存活和生殖情况。结果表明,该蜂在13—30℃(75％R.H.)范围内,卵至羽化的发育速率与温度呈逻辑斯蒂曲线关系;发育起点温度为10.1±0.03℃,有效积温常数为140.2±0.29日度;幼期存活率在26℃左右最高;成虫寿命随温度升高而缩短,生殖力以23—28℃最高;内禀增长力(r_m)随温度升高而增大,28℃时达最大,随后急剧下降,至31℃时巳为负值。低湿和高湿在低温下有使发育速率减缓,而在适温和高温下则有使发育速率加快的趋势;低温低湿和高温高湿有使幼期存活率下降的趋势;在低温、高温下,75％R.H.对成虫存活、生殖最有利,95％R.H.次之;在适温下湿度对生殖力无影响,成虫寿命在低湿下最短。33℃下,3种湿度下均未产生雌性后代。     

旅游对南湾猕猴种群增长的影响

１９８４－１９８９年到海南省南湾旅游观猴人数年均增长６９．８％,现每年接待游人逾１０万人次,观察研究结果,发现开发旅游后猕猴繁殖率下降,新生猴死亡率提高,人工投喂半驯化猴群延长了猴群分群时间,导致猕猴种群增长减慢,在热带地区人工投食对猕猴的敏     

温度对玉米蚜种群增长的影响

研究了温度对玉米蚜RhopalosiphummaidisFitch种群存活率、生殖率及内禀增长率的影响 ,同时测定了不同温度条件下玉米蚜种群的净增殖率、周限增长率、种群倍增时间及稳定年龄组配等种群参数。在 1 0℃和 3 5℃条件下 ,玉米蚜若蚜的死亡率较高 ,特别是 4龄若蚜 ;2 5℃最适宜玉米蚜的生长、发育和繁殖 ,其种群增长最快     

常见元素及其浓度对榆干离褶伞菌丝生长的影响

为研究常见元素对榆木离褶伞菌丝生长的影响,通过其在含有不同离子浓度的PDA培养基中生长速度的观察,探讨不同元素及其浓度对榆木离褶伞菌丝生长的影响。结果表明:1 mg/mL的Mg(Ac)2、KH2PO4和CaO促进菌丝生长;5,10 mg/mL的Mg(Ac)2、CaO,10mg/mL的Na2SO4、NaCl抑制菌丝生长;其他种类及浓度的离子对菌丝生长的影响不显著。     

Intraflagellar Transport 80 Is Required for Cilia Construction and Maintenance in Paramecium tetraurelia

Intraflagellar transport (IFT) represents a bidirectional dynamic process that carries cargo essential for cilia building and the maintenance of ciliary function, which is important for the locomotion of single cells, intracellular and intercellular signalling transduction. Accumulated evidence has revealed that defects in IFT cause several clinical disorders. Here, we determined the role of IFT80, an IFT‐B protein that is mutated in Jeune asphyxiating thoracic dystrophy. Using the RNAi method in the ciliate Paramecium as model, we found that loss of IFT80 prevents cilia biogenesis and causes strong cell lethality. A specific antibody against IFT80 was also prepared in our study, which labelled IFT80 in cilia of Paramecium. GFP fusion experiments were performed to illustrate the dynamic movement of IFT‐A and IFT‐B proteins in cilia of Paramecium; then, we found that the depletion of IFT80 in cells prevents IFT‐A and IFT‐B proteins from entering the cilia. Our results showed the distribution change of other IFT proteins in cells that were depleted of IFT80, and we discuss the possible roles of IFT80 in Paramecium.     

pH值对大乳头水螅种群增长、无性生殖及3种抗氧化酶活力的影响

应用种群累积培养法,就培养液pH值对大乳头水螅（Hydra magnipapillata）的生存、种群增长、无性生殖以及水螅的超氧化物歧化酶（SOD）、过氧化氢酶（CAT）、谷胱甘肽过氧化物酶（GSH—PX）3种抗氧化酶活力的影响进行了探讨。结果表明,水螅存活的pH上限为10．5,下限为4．0,水螅存活的最适pH范围为5．5～9．5;pH值对水螅种群增长有显著影响,种群密度及种群瞬时增长率均随pH的不同而明显改变。培养15d后,除了pn4．0时水螅种群为负增长外,其他pH梯度下的水螅种群为正增长,其中pH6．5时水螅种群密度最高。以pH6．5为起始点,随着培养液酸性或碱性的增强,水螅种群密度整体都呈递减趋势。水螅SOD活力的转折点在pH6．5,当pH值偏离6．5时（酸性或碱性增强）,水螅SOD活力整体呈明显上升趋势;但水螅GSH—PX和CAT活力的转折点却在pH7．0,当pH值偏离7．0时（酸性或碱性增强）GSH—PX和CAT活力整体呈明显下降趋势。pH6．5时水螅SOD活力最低与pH6．5实验组水螅的无性出芽生殖率最高之间可能存在一定的内在联系。本文研究结果可为实验室培养水螅提供适宜的pH值指标。     

水培条件下不同磷水平对毛竹实生苗生长发育的影响

以毛竹(Phyllostachys edulis)实生苗为材料,采用Hoagland营养液水培方法,研究不同磷浓度下毛竹生长、根系发育、激素含量等的差异。结果表明:磷浓度较低时,可以促进毛竹实生苗根系长度及根系总表面积的增长。随着磷浓度的增加,实生苗生物量干重及根冠比呈先上升后下降趋势,磷浓度为1 mmol L-1时达到最大。无磷处理时,根中的IAA、ZR、GA3和ABA等4种内源激素含量随着处理时间的延长均先升高再降低;其他浓度磷处理根中IAA、ZR和GA3(0.5 mmol L-1磷除外)含量随着处理时间的延长大致呈先降低后升高的趋势,而ABA(0.5 mmol L-1磷除外)含量随着处理时间的延长变化不明显。不同浓度磷处理,叶片中IAA、GA3和ABA含量总体上呈下降趋势,ZR含量总体上呈上升趋势。以上结果表明不同浓度的磷处理对毛竹内源激素含量的变化有显著的影响,而内源激素含量变化与毛竹实生苗根系变化密切相关。     

Understanding Current and Potential Consequences of Population Growth

In three semiguided inquiry lessons on population biology, students use models and simulations to examine population trends and make projections. They are guided to create and evaluate data and to use algebraic and geometric representations to examine biotic and logistic growth models as part of examining human population growth. As they recognize the relationship between population growth and resources, they explore and propose solutions for addressing complex socioscientific problems. The underlying mathematics and science concepts of these learning cycle lessons can help students understand the complexity of environmental issues and prepare them to reason in an informed manner when they encounter debates on population and environmental issues that are often voiced in political arenas.     

How Population Growth Affects Linkage Disequilibrium

The “LD curve” relates the linkage disequilibrium (LD) between pairs of nucleotide sites to the distance that separates them along the chromosome. The shape of this curve reflects natural selection, admixture between populations, and the history of population size. This article derives new results about the last of these effects. When a population expands in size, the LD curve grows steeper, and this effect is especially pronounced following a bottleneck in population size. When a population shrinks, the LD curve rises but remains relatively flat. As LD converges toward a new equilibrium, its time path may not be monotonic. Following an episode of growth, for example, it declines to a low value before rising toward the new equilibrium. These changes happen at different rates for different LD statistics. They are especially slow for estimates of σd2, which therefore allow inferences about ancient population history. For the human population of Europe, these results suggest a history of population growth.     

食物浓度对三个地理品系角突臂尾轮虫种群增长、个体大小和卵体积的影响

以浓度分别为 3 0× 10 6、 6 0× 10 6、 9 0× 10 6和 12 0× 10 6cells/mL蛋白核小球藻 (Chlorellapyrenoi dosa)为食物 ,在温度为 (2 5± 1)℃下 ,应用群体累积培养法研究了食物浓度对分布于长江、珠江和淮河水系的 3个地理品系的角突臂尾轮虫 (Brachionusangularis)种群的增长、个体和卵的体积的影响。结果表明 ,食物浓度、地理品系及两者间的交互作用对轮虫种群增长率、个体和卵的体积均有显著影响。同一食物浓度下 ,广州品系的种群增长率最大 ,芜湖品系的个体和卵体积最大 ;同一品系中 ,当食物浓度为 9 0× 10 6cells/mL时轮虫有较大的种群增长率。各品系轮虫的种群增长率与食物浓度均呈曲线相关 ,但种群增长率达最大时所需的食物浓度在各品系间存在着差异。在食物浓度和品系两因素中 ,品系对轮虫个体体积有较大的影响     

Effects of static magnetic fields on growth of Paramecium caudatum

Little is known about the influence of magnetic fields on growth of primitive eukaryotes such as the ciliate Paramecium. The latter are known to exhibit interesting characteristics such as electrotaxis, gravitaxis, and membrane excitability not commonly encountered in higher organisms. This preliminary study reports the effects of static magnetic fields on growth of Paramecium caudatum. The microorganisms were either permanently or 24 h on-and-off exposed to North and South polarity magnetic fields of average field gradient 4.3 T/m, for a period of 96 h. The growth rate and lag phase of all exposed populations were not significantly different from control ones exposed to normal geomagnetic field (P > .05). However, a significant negative shift in t(max) (time taken for maximum growth) of 10.5%-12.2% and a significant decrease (P < .05) in population size of 10.2%-15.1% during the 96 h of experimental conditions were recorded for exposed populations compared to control. Our results suggest that magnetic fields, irrespective of polarity and exposure period reduce Paramecium growth by triggering early senescence of the population. The mechanisms underlying the small changes in population growth are unknown at this level, but various hypotheses have been suggested, including disorganization of swimming patterns resulting from (i) changes in cell membrane electric potential due to high speed movement through a gradient magnetic field and (ii) thermodynamic effect of anisotropic magnetic energies on cell membrane components affecting functioning of calcium channels. Altered swimming movements could in turn affect highly orchestrated processes such as conjugation, essential for survival of the organisms during development of adverse environmental conditions as thought to occur in the closed culture system used in this study.     

培养基组分及pH值对梨花粉萌发和花粉管生长的影响

采用花粉液体培养法研究不同培养基组分和pH值对梨花粉萌发和花粉管生长影响.结果表明:培养基内硼酸、氯化钙、PEG-4000、蔗糖、葡萄糖、麦芽糖、山梨醇、果糖在一定浓度范围内,对花粉萌发及花粉管生长起促进作用,但超过一定浓度时起抑制作用;最适的培养基组分为:30mmol/LMES、0.01%硼酸、0.03%CaCl2·2H2O、15%PEG-4000、5%果糖 或5%山梨醇、10%蔗糖 ,最适的pH值为6.5.在该培养基内梨花粉萌发率约为59.2%,花粉管生长长度为966.3μm.     

The Effect of Major Nutrient Elements on the Growth and Population Homogeneity of the R,S, and M Dissociants of Pseudomonas aeruginosa and the Glucose Oxidation and Fermentation Pathways

The population homogeneity of the stationary-phase monocultures of Pseudomonas aeruginosa dissociants was studied as a function of the initial content of major nutrient elements (C, N, and P) in the cultivation medium. The monocultures of the dissociants remained homogeneous during cultivation if the initial concentrations of the major nutrient elements were either sufficiently high or, conversely, very low, but became heterogeneous during cultivation in unbalanced (with respect to the major nutrient elements) media. At an initial concentration of nitrate in the medium equal to 0.07% or phosphate equal to 0.004–0.014%, the initially homogeneous population of R dissociant cultivated to the stationary growth phase turned out to contain 30–40% of S-type cells, whereas the initially homogeneous population of S dissociant was found to contain 50–80% of M-type cells. The population of M dissociant remained homogeneous throughout the cultivation period. R dissociant grew better at sufficiently high concentrations of glucose, nitrate, and phosphate in the medium, whereas M dissociant grew better when the initial concentrations of these nutrients were low. During the cultivation of R dissociant, the pH of the medium changed insignificantly, and the C/P ratio (the ratio of the carbon and phosphorus consumed during growth) was minimal (among the three dissociants), indicating that the R dissociant accomplishes the oxidative pathway of glucose metabolism. During the cultivation of the M dissociant, the pH of the medium dropped to 3.4–3.9, and the C/P ratio was maximal, indicating that this dissociant accomplishes the fermentative pathway of glucose metabolism. During the cultivation of the S dissociant, the pH of the medium and the C/P ratio exhibited variations, indicating that this dissociant triggers its pathways of glucose metabolism.