Commensalism is a relationship in which one organism benefits and the other organism is neither benefited nor harmed. Mutualism is a relationship in which both organisms benefit. Parasitism is a relationship in which one organism benefits and the other organism is harmed. Predation is a relationship in which one organism hunts the other organism for food.

 An ecosystem consists of communities of organisms interacting with their environment. Abiotic components are nonliving aspects of the environment (sun, wind, soil, water, etc), and biotic components are living aspects of the environment.

The zebra benefits because the oxpecker rids the zebra of harmful parasites and the zebra receives a warning from the oxpeckers when predators approach; the oxpecker benefits because the parasites serve as a food source. In this scenario, both organisms benefit from the relationship. Commensalism is a relationship in which one organism benefits and the other organism is neither benefited nor harmed. Mutualism is a relationship in which both organisms benefit. Competition is a relationship where both organisms are harmed, as they seek the same limited resource. Predation is a relationship in which one organism hunts the other organism for food.

 A tick benefits as they use the blood as a food source, and the dog is harmed as it can receive diseases from the tick, and if the tick consumes enough of their blood, the dog can become anemic. Commensalism is a relationship in which one organism benefits and the other organism is neither benefited nor harmed. Mutualism is a relationship in which both organisms benefit. Parasitism is a relationship in which one organism benefits and the other organism is harmed. Predation is a relationship in which one organism hunts the other organism for food.

Darwin observed that the finches found on the Galapagos had adapted different sized beaks to eat different diets. By doing this, the birds had evolved to eat diets that would be inedible by other finches. This concept of a "niche" means that different species will exploit and use their environment in different ways.

The inheritance of traits through discrete units called alleles was not a part of Darwin's theory of evolution. A monk named Gregor Mendel developed the theory of inheritance through alleles. Darwin's theory did not propose a method of inheritance, and Darwin was unaware of Mendel’s work. The works of Darwin and Mendel were later combined by scientists to create the modern theory of evolution.

The finches' beaks are highly adapted to their preferred diet. Therefore, this is an excellent example of adaptation. Acclimation occurs on a very short-term basis and does not apply to speciation. Stabilizing selection decreases the amount of genetic diversity among a population, and does not promote speciation as seen among finches. Heredity is simply the degree to which a parent's genes are passed to its offspring and is not demonstrated by this example.

The answer is directional selection. This environmental change will cause a shift in the mean beak size of the population towards smaller beaks because their food resource was not affected. There is selection against long beak size only.

Artificial selection is a process by which humans have modified species over many generations by selecting and breeding individuals that possess desired traits. The result of such a selection is a narrowing of the traits originally present from its ancestors. The goal of artificial selection is generally to make certain desired traits fixed in the population, with an allele frequency of 100%. These traits are relatively arbitrary, and may be wild type, recessive, advantageous, or disadvantageous. The key factor is a decrease in genetic variability in a small population.

Examples of artificial selection include the derivation of individual breeds of dog and the production of genetically specific lab mice.

Disruptive selection occurs when conditions in a habitat favor individuals that are on the extremes of the phenotypic range, instead of individuals with intermediate phenotypic traits. In the example provided in the question, dark-colored moths and light-colored moths each have regions of the habitat where they gain an advantage, but intermediate grey coloring is not favored in any region of the habitat. As a result, both extremes will experience positive selection, while the intermediate will decrease, giving rise to a disruptive selection trend.

Stabilizing occurs when the intermediate phenotype is favored over either extreme. Directional selection occurs when a single extreme is favored over any other phenotype. Artificial selection is the result of human manipulation of breeding, selecting for chosen traits.