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: 29078

#Unit 10. Ecological Principles

A specific kind of parasitism proposes that  in which cuckoos or cowbirds repeatedly check their host’s nests and destroy all eggs if their owner is not present. If the parasite egg has been removed, they destroy the host’s nest and kill or injure the nestlings, this is an example of____

#Question id: 29079

#Unit 10. Ecological Principles

You observed the two species of barnacles, P. aurelia and P. caudatum, occupy upper and lower strata of intertidal rocks, respectively. Only when P. caudatum was removed by you from the lowers strata, P. aurelia could occupy both the upper and lower strata. From the choice given below what would be your inference from these observations.

#Question id: 29080

#Unit 10. Ecological Principles

Invasive species are less impacted by enemies than native species. An explanation for the better growth and propagation of invasive species in comparison to their native counterparts is provided by which one of the following hypotheses?

#Question id: 29081

#Unit 10. Ecological Principles

#Question id: 29082

#Unit 10. Ecological Principles

There are some major anthropogenic atmospheric gases causing the greenhouse effect, which of the following gas has the most powerful greenhouse effect?

#Question id: 29083

#Unit 10. Ecological Principles