Hybrid inviability offspring are infertile or otherwise deformed or unable to reproduce. Introduction of apples by colonists led to appearance of new form, the apple fruit fly, from the original populations of hawthorn fruit flies. Population of hawthorn flies that began to emerge earlier fed on apples, which bloom earlier than hawthorns. B. Niche is an exploitable zone that can be occupied, or a role that can be played, by an organism in a specific habitat. Felis is genus name shared by all small cats, silvestris and nigripes are specific epithets unique to those cat species.
Common ancestor is defined based on characteristics shared by all members in the group.
The more derived characters any two organisms share, the more recently they will have shared a common ancestor, compared to other organisms. C. Discrepancies in classification can result between cladistic analysis and classical systematics. Cladistics focuses only on evolutionary relatedness, while classical systematics uses phylogenetic evidence along with other information and may give disproportional weighting to some traits relative to others.