Stabilizing selection favors the intermediate phenotypes in a population while disruptive selection favors extreme phenotypes. Artificial selection is frequently practiced by humans in breeding livestock, pets, and crops. Sexual selection is dependent on interaction between males and females within a population. Domestic selection is not a real term.

Quantifiable traits, like beak size, in a population tend to form a bell curve when graphed. Selection that leads to more individuals on either end of the graph compared to individuals in the center is disruptive, and in this case leads to a lack of medium sized birds since birds with either small or large beaks were favored. Selection that favors individuals on one side of the graph is directional, and selection that favors individuals in the center of the graph is stabilizing.

Disruptive selection happens when the environment favors individuals on the extreme ends of a phenotype.

Directional selection favors individuals on one end of a phenotype (for example, a different environment may only favor black beetles, but not white or gray).

Stabilizing selection favors against extreme phenotypes (for example, a different environment may favor gray beetles, but not black or white beetles). 

Mitosis does not create genetic variation. The primary roles of mitosis are growth and healing.

Crossing over refers to the exchange of genetic material between chromosomes during metaphase I of meiosis, and is largely responsible for enhancing the genetic variation of eukaryotes. Mutation is necessary to introduce new genetic factors and adaptations into a population, thus furthering evolution and promoting variation.

Nodes specifically indicate the most recent common ancestor between the two branches. For example, the ancestor found at the node joining branches from humans to branches from dogs would represent the most recent link between the two branches.

Convergent evolution describes the independent evolution of traits at different points on a phylogeny, and is not related to nodes. Kingdoms and domains are very broad categories. They can be represented by nodes, but only at a very global level.

Genus and species are the two taxonomic classifications that are used to represent the scientific name of an organism. The hierarchy of the binomial classification system is (from the top tier to the bottom): kingdom, phylum, class, order, family, genus, species. Kingdom gives the broadest classification of an organism, while species gives the most specific. The most specific classifications are used to name the organism.

For example, the scientific name for a house cat is felis catus. This indicates that houses cats, like some other species, are in the genus felis and have the unique species tag catus.

The full classification for a house cat would be: anamalia (kingdom), chordata (phylum), mammalia (class), carnivora (order), felidae (family), felis (genus), catus (species).

Cladograms show evolutionary relatedness, usually based on the similarity of the DNA sequences between different species. The closer two branches of the cladogram are to each other, the more closely related the organisms are to each other. The ends of the branches indicate a common ancestor shared by all of the species of that branch. Cladograms do not show geographic relationships. Although primitive cladograms were formulated based on physical characteristics of animals, now, DNA analysis provides a much more accurate comparison between species. Furthermore, cladograms are not limited to animals.

Each branch in the tree represents a break from the common ancestor at the bottom. A and B are both branches off of the same larger branch that C is also a branch of. D, E and F branched off from the common ancestor earlier than A, B, or C. In general, branches that are closer together, and are on the same larger branch, represent organisms which are closely related.

In the system of biological classification, organisms are classified in a hierarchy, or taxonomy. The highest levels of classification are the most inclusive, while the lower levels become more and more specific until a single species is identified. From most inclusive to least inclusive, organisms are assigned a kingdom, a phylum, a class, an order, a family, a genus, and finally a species.

Organisms sharing the same classification at less inclusive levels will be more closely related. For example, two organisms sharing the same genus will be more closely related than those who only share the same family. Of the given answer choices, family is the most specific level of classification.

Phylogenetics is the study of relationships between organisms and groups of organisms. This is done through the production of phylogenetic trees, which are used to describe these relationships. To make phylogenetic trees, scientists use molecular sequencing and/or morphological similarities in order to characterize the relationships between organisms.