The chain concept is a theoretical model to study the energy flux in ecosystems. Actually, in an ecosystem the organisms are part of several interconnected food chains, forming a food web. Therefore, the chain is a theoretical linear sequence and the web is a more realistic representation of nature in which the food chains interconnect forming a web.
Image Diversity: food web
Microscope resolution increases as the wavelength of radiation used to illuminate the specimen decreases. A) True B) False
Even on the best light microscopes, increasing total magnification beyond 1500 cannot result in better resolution of the image. A) True B) False
Differential Interference Contrast microscopy A) compares two identical specimens on the same microscope. B) illuminates the specimen with light of two different colors. C) illuminates the specimen with light of two different phases. D) illuminates the specimen with both reflected and transmitted light
In a compound microscope, the primary image is formed by an objective lens and enlarged by the optical lens to reveal a virtual image. A) True B) False
"Parfocal" refers to microscopes with multiple objectives where A) objectives are used in pairs for stereoscopic effects. B) each objective has the same working distance above the specimen. C) each objective is positioned to be in focus at the same stage height. D) sequential objectives increase power by a factor of two.
Which of the following is NOT equivalent to 10 micrometers. A) 0.0001 cm B) 0.01 mm C) 10,000 nm D) 100,000 Angstroms
Phase Contrast microscopy A) Continuously changes the phase of the incident light from the condenser to improve contrast in the specimen. B) Uses circular filters in the condenser and objective to give contrast to parts of the cell with different refractive indices. C) Uses special lenses to distinguish between solid and liquid phases of the cell. D) Uses special lenses to change the color of light passing through them
Which of the following statements about Transmission Electron Microscopy is not true. A) The specimen must be stained with osmium or other heavy metal. B) The specimens are placed in a high vacuum for viewing. C) The specimens must be sliced very thin, 20-100 nm in thickness. D) The beam is focused by electromagnetic lenses
Which of the following statements is most correct about Atomic Force Microscopy (AFM)? A) AFM can visualize protein bound to DNA molecules. B) AFM can visualize unfixed specimens in water or buffer. C) AFM moves a very sharp tip over the surface of the specimen to "feel" its shape. D) All the statements above are true
Which of the following statements is most correct about the differential Gram stain? A) Crystal violet differentially stains Gram positive cells. B) Gram's iodine differentially stains Gram positive cells. C) Acetone differentially destains Gram negative cells. D) Saffron red differentially stains Gram negative cells
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