A biologist began studying a population of bullfrogs. In 1998, she found that most of the male frogs croaked, but some did not. A bat species know to prey on male frogs migrated to the area in 2005. The biologist returned to the area in 2008 and repeated population counts of male frogs. The table shows her data. Based on the data, which statement is a plausible explanation for the change in the frog population between 2004 and 2008?

answer: land bridge theory. land bridge theory held that shifting portions of dry land explained the finding of identical species on different continents. plate tectonic theory eventually eliminated the land bridge theory.

how do heroes resolve conflicts in beowulf?

question 15 options:

they sue each other in court

they get a mediator

the seek counseling

they get even or take revenge

explanation:

step 1: initiation

initiation is the beginning of transcription. it occurs when the enzyme rna polymerase binds to a region of a gene called the promoter. this signals the dna to unwind so the enzyme can ‘‘read’’ the bases in one of the dna strands. the enzyme is now ready to make a strand of mrna with a complementary sequence of bases.

step 2: elongation

elongation is the addition of nucleotides to the mrna strand. rna polymerase reads the unwound dna strand and builds the mrna molecule, using complementary base pairs. there is a brief time during this process when the newly formed rna is bound to the unwound dna. during this process, an adenine (a) in the dna binds to an uracil (u) in the rna.

step 3: termination

termination is the ending of transcription, and occurs when rna polymerase crosses a stop (termination) sequence in the gene. the mrna strand is complete, and it detaches from dna.