What is the principle of superposition? A. The layers of sediment on the bottom are the oldest. B. All layers of sediment are identical. C. In a given region, all layers of sediment form at the same time. D. The geologic processes of today are very different from those in the past.

You have been asked to lead a demonstration for the undergraduate microbiology lab course about the uses of negative staining when studying bacteria. a "negative" stain does not stain the bacterial cell itself but stains the space between cells. under magnification, the acidic (negativelycharged) nature of the stain will be repelled by the negatively charged bacterial cell wall and willleave the cell colorless in a stained background. negative stains are used primarily to reveal the presence of negatively charged bacterial capsules; therefore, they are also called capsule stains. encapsulated cells appear to have a halo surrounding them. the negative stain procedure does not require heat fixation, which limits any chances of alteration in bacterial cell shape and size. the bacterial suspension is added to a drop of stain, such as nigrosin or eosin, and drawn across the glass slide using a coverslip. nigrosin staining-not safranin staining-of klebsiella pneumoniae will allow for the visualization of the cell shape and the determination of the presence of a capsule. true/false

Female luna moths (actias luna) attract males by emitting chemical signals that spread through the air. a male hundreds of meters away can detect these molecules and fly toward their source. the sensory organs responsible for this behavior are the comblike antennae visible in the photograph shown here. each filament of an antenna is equipped with thousands of receptor cells that detect the sex attractant. based on what you learned in this chapter, propose a hypothesis to account for the ability of the male moth to detect a specific molecule in the presence of many other molecules in the air. what predictions does your hypothesis make? design an experiment to test one of these predictions.

Need ! will give 20 points! what are two ways that diatoms differ from slime molds? the external coverings of diatoms are made up of (silica, chitin or peptidoglycan), while slime molds have cell walls containing (silica, peptidoglycan or chitin). diatoms are (chemoheterotrophs, photoautotrophs or chemoautotrophs) because they make food through photosynthesis, while slime molds are (heterotrophs, phototrophs or autotrophs) because they eat decaying plant matter.