Until the middle of the nineteenth century, all peppered moths (biston betularia) observed around manchester, england, were light in color. in 1845, a single black peppered moth was reported. as manchester became more industrialized and dark soot began to cover the bark of the trees, the frequency of black moths increased greatly. the change in proportion of light and dark forms resulted
select one:

a. disruptive selection.
b. directional selection.
c. stabilizing selection.
d. genetic drift.
e. increased mutation

B. directional selection.

Explanation:

Changes in environmental conditions over time makes the natural selection to favor one of the extreme phenotypes due to its better survival and reproductive fitness over the other phenotypes. The favored phenotype gradually becomes abundant in the population. This type of natural selection is called directional selection.  

In the given example, industrialization led to the deposition of dark soot over the barks of the tress. The black moths had better survival success as they could blend themselves with the dark background. The light-colored moths were easily picked by predators. This led to a gradual increase in the number of black colored moths in the population. Since one of the extreme phenotypes (black color) was favored, the process is called directional selection.  

water is a polar molecule. a chemical bond is a force of attraction between atoms or ions. bonds form when atoms share or transfer valence electrons. atoms form chemical bonds to achieve a full outer energy level, which is the most stable arrangement of electrons. so, false

explanation:

in h2o molecule, two water molecules are bonded by a hydrogen bond but the bond between two h - o bonds within a water molecule are covalent. the greater the electronegativity difference, the more ionic the bond is. bonds that are partly ionic are called polar covalent bonds. nonpolar covalent bonds, with equal sharing of the bond electrons, arise when the electronegativities of the two atoms are equal.