Select ALL the correct answers. Some individuals of a particular species of sea bird underwent a genetic mutation that resulted in larger beaks. The larger size of beaks helped
these birds to break open dams and other mollusks for food. It also helped them defend themselves against predators. After many generations,
almost all of the birds in the population had big beaks. For which two reasons did this phenomenon occur?

A. natural selection

B. mechanical Isolation

C. prezygotic barriers to reproduction

D. high genetic variation in the species

small, big, or no change could occur in the phenotype. it could cause something as simple as a cats ears to curl backwards or something as frighting as death. it could also occur in the protien-coding area and have an effect on that but no effect on the amino acids. what has to occur is a changing in the hox gene or the control gene.

igneous rocks are formed by solidification of cooled magma (molten rock), with or without crystallization, either below the surface as intrusive (plutonic) rocks or on the surface as extrusive (volcanic) rocks.  

the composition depends on the source magma. there are almost a thousand types of composition found till now.  

hope this