Sexual reproduction greatly increases the variation that could operate on

Natural Selection

Explanation:

Sexual selection impart new gene combinations to the individuals by the process of gamete formation and random fertilization of gametes.

Natural selection favors the beneficial variations that impart survival and/or reproductive fitness to the individuals. This results of evolution of population consisting of better adapted individuals.

For example, natural selection favors the bacteria with antibiotic resistance genes if antibiotics are present in surroundings.

answer:

the water molecules are transferred from the roots to the stem or top parts of the tall tree because of important properties of water which are adhesion, cohesion and capillary action. cohesion is the property of water molecules keeps water molecules in a combined state by sharing of bonds between them at the atomic level. adhesion allows the interaction of water molecules with other substances or substrate. adhesion will cause the attachment of water molecules to the wall of the vessel (xylem) of the plant. capillary action occurs when the adhesive force to the vessel wall is stronger than the cohesive force between water molecules. capillary action mimics the transfer of water from a tube or pipe. in this way water utilizes its property to transfer water from down to top level of the plant.