Mutations that block expression of the E-cadherin gene are thought to be an important step in metastasis. To better understand how loss of E-cadherin contributes to metastasis, scientists created two cell lines that differed in their expression of E-cadherin. One cell line expressed normal E-cadherin, but at 10% of the usual levels. The other cell line expressed normal E-cadherin at the usual levels, and also, at high levels a mutant form that included the cytoplasmic domain but lacked the rest of the protein. Both cell lines exhibited strongly reduced cell adhesion in culture. However, only the cell line with reduced expression of normal E-cadherin metastasized when introduced into mice.

Which of the following hypotheses is most consistent with the observations on cell adhesion and metastasis in these cell lines?

#Question id: 11396

#Unit 9. Diversity of Life Forms

Carl Woese and collaborators identified two major branches of prokaryotic evolution. What was the basis for dividing prokaryotes into two domains?

#Question id: 11397

#Unit 9. Diversity of Life Forms

Which statement about the domain Archaea is false?

#Question id: 11398

#Unit 9. Diversity of Life Forms

Assuming that each of these possesses a cell wall, which prokaryotes should be expected to be most strongly resistant to plasmolysis in hypertonic environments?

#Question id: 11399

#Unit 9. Diversity of Life Forms

The thermoacidophile, Sulfolobus acidocaldarius lacks peptidoglycan. What is likely to be true of this species?

1. It is a bacterium.

2. It is an archaean.

3. The optimal pH of its enzymes will lie above pH 7.

4. The optimal pH of its enzymes will lie below pH 7.

5. It could inhabit certain hydrothermal springs.

6. It could inhabit alkaline hot springs.

#Question id: 11400

#Unit 9. Diversity of Life Forms

What is the primary ecological role of prokaryotes?

#Question id: 11401

#Unit 9. Diversity of Life Forms

In a hypothetical situation, a bacterium lives on the surface of a leaf, where it obtains nutrition from the leafʹs nonliving, waxy covering, while inhibiting the growth of

other microbes that are plant pathogens. If this bacterium gains access to the inside of a leaf, it causes a fatal disease in the plant. Once the plant dies, the bacterium

and its offspring decompose the plant. What is the correct sequence of ecological roles played by the bacterium in the situation described here? Use only those that

apply.

1.  nutrient recycler          2.  mutualist            3.  commensal              4.  parasite          5.  primary producer