Question

* Which of these are routinely used to obtain a pure culture of bacteria?

a. swan necked flasks b. agar streak plates c. dilution plates d. microscopes

* The cells of all species of Bacteria and Archaea are very small, and:

a. must be stained before they can be seen using light microscopy

b. can only be seen using electron microscopy

c. can only be seen if they are first Gram stained

d. none of the above

* Prokaryotes evolved early on in the history of the Earth:

a. so their physiology has little in common with Eukaryotes

b. so many aspects of their physiology also occur in Eukaryotes, which evolved much later in in the history of the Earth

c. and Eukaryotes evolved independently at a much later time in the history of the Earth

d. at about the same time that Eukaryotes first appeared on Earth

Answer 1

1. (b) agar streak plates

Explanation:

The streak-plate procedure is designed to isolate pure cultures of bacteria, or colonies, from mixed populations by simple mechanical separation.

2. (a) must be stained before they can be seen using light microscopy

Explanation:

Because microbial cytoplasm is usually transparent, it is necessary to stain microorganisms before they can be viewed with the light microscope.

3. (b) so many aspects of their physiology also occur in Eukaryotes, which evolved much later in in the history of the Earth

Explanation:

Compared to prokaryotic organisms such as bacteria, plants and animals have a relatively recent evolutionary origin. DNA evidence suggests that the first eukaryotes evolved from prokaryotes, between 2500 and 1000 million years ago.

The hypothesis that eukaryotic cells evolved from a symbiotic association of prokaryotes - endosymbiosis - is particularly well supported by studies of mitochondria and chloroplasts, which are thought to have evolved from bacteria living in large cells.