. When birds migrate into or out of a defined population and mate with birds from another population, the existing pool of genes may be altered. Migration can increase or decrease gene
frequencies in populations, resulting in...

A. Greater genetic variation, which may enhance chances of survival

B. Less genetic variation, which will not influence chances of survival at all

C. Selective breeding, which may enhance chances of survival

D. Natural selection, which will not influence chances of survival at all

Crossing over is a method of (blank)?

Describe how viruses and bacteria can be used as biological weapons. what are some of the potential threats and potential benefits? do you agree with the use of viruses and bacteria as biological weapons? why or why not?

The diagram below shows the layers of a rock having a trilobite: a rock column labeled rock is shown. the column has three layers. the bottommost layer of the rock has one shaded rhomboid shape, the middle layer has a rhombus with a diagonal along with two identical organisms marked as, trilobite, in the key, the top layer has two semicircles. a key is shown on the right side of the diagram. the shaded rhombus is marked as a, the rhombus with the diagonal is marked as b, the semicircle is marked as c which statement about the rock fossils is true?