Which forestry practice decreases competition and improves the overall health and productivity of a forest? a. desertification b. clear-cutting c. slash-and-burn d. thinning

Answer is (D) Thinning

Thinning is the forestry practice of selectively removing certain trees to increase the productivity of the forest. Example eucalyptus trees have a higher water consumption and demand. Now if there are several such trees in a forest, it will affect the water demand of the other trees. It will be competing for resources. Hence by selective removal of such trees, the health of a forest can be boosted.

genetic variation can be caused by mutation (which can create entirely new alleles in a population), random mating, random fertilization, and recombination between homologous chromosomes during meiosis (which reshuffles alleles within an organism's offspring).