Cervical lymphadenitis is usually caused by a viral upper respiratory infection. The key symptom of lymphadenitis is the presence of a painful mass in the cervical area, often accompanied by fever, runny nose, sore throat, and cough.
Question and answer. Which of the following defines evolution? a change in environmental conditions a change in an animal's physical traits a change in a population's gene pool a change in an individual's genetic. makeup. Evolution is a change in a population's gene pool.
Overview of Evolution within a Lineage. Evolution is a change in the gene pool of a population over time; it can occur due to several factors. Three mechanisms add new alleles to the gene pool: mutation, recombination and gene flow. Two mechanisms remove alleles, genetic drift and natural selection.