The Galapagos finches were an important clue to Darwin's thinking about the origin of species. These finches are believed to have descended from a single ancestral species that colonized the Galapagos archipelago, America, over a short period of time. The Galapagos finches differ in their beak shape and size. Different species feed on seeds that vary in size and hardness. Which of the following is the most likely explanation for these patterns?

#Question id: 2026

#Unit 4. Cell Communication and Cell Signaling

Which of the following statement is FALSE regarding MHC proteins

#Question id: 1742

#Unit 4. Cell Communication and Cell Signaling

The T-cell receptor link to MHC–peptide is enhanced by interaction between MHC class II on the antigen-presenting cells with the following molecule on the T-cell:

#Question id: 7265

#Unit 5. Developmental Biology

Following statement regarding to the cascade of regulated RNA splicing controls drosophila sexual differentiation.

A. The Sex-lethal (Sxl) protein, encoded by the sex-lethal gene, is the first protein to act in the cascade and present only in female embryos.

B. Early in development, the Sxl gene is transcribed from a promoter that functions only in male embryos.

C. Later in development, this male-specific promoter is shut off, and another promoter for sex-lethal becomes active in both male and female embryos.

D. In male embryos, however, in the absence of early Sxl protein, exon 3 of the sex-lethal pre-mRNA is spliced to exon 2 to produce an mRNA that contains a stop codon early in the sequence.

Which of the following is correct?

#Question id: 10532

#Unit 2. Cellular Organization

A  closed, self-sealing solvent-filled vesicles that are bounded by only a single bilayer, known as:

#Question id: 11297

#Unit 10. Ecological Principles

What is the difference between gross and net primary production?