Who determined that the cholera outbreak in 1850s London was due to contaminated water and approached the problem by removing the pump handle at the contaminated site?
A. Pasteur
B. Snow
C. Koch
D. Smith
B. Snow
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It is believed that phototrophy arose approximately 3.3 billion years ago in
A) Bacteria. B) Archaea. C) Eukarya. D) LUCA.
The steps necessary for hearing include (1) amplification of sound waves, (2) transfer of sound vibrations to fluid pressure waves, and (3) mechanoreception by hair cells of the cochlea. How are the sound vibrations transferred to fluid pressure waves?
A. by the bones of the middle ear B. through the oval window C. by the tympanic membrane D. by the action of the vestibular system
An electron microscope must use electromagnet 'lenses'shaped like donuts to direct the electrons onto the specimen. Why aren't they solid, like the lenses in a light microscope?
A. A magnetic field cannot be applied across a completely solid object-there must be an opening within the object for the field to be applied through. B. The user has to be able to physically look through the magnets to focus the beam of electrons onto the specimen, since the metal of the magnets is opaque. Without a hole in the middle, the user wouldn't be able to see! C. The electrons would destroy the electromagnet material unless there was a physical hole for them to travel through on their way to the specimen. D. Electrons are particles, and particles cannot travel through a solid item. The hole in the middle allows them to travel from the source of the electrons to the specimen.
What kinds of general observations cause one to conclude that development is the result of variable gene activity?
What will be an ideal response?