Species and populations are probably the two most commonly used ecology terms, but they are often difficult concepts to grasp. Throughout this chapter, they will be discussed in detail, expanding on the definitions from previous chapters and explaining why there are no universally acceptable definitions.
Jefferson County, Arkansas is a county located in the U.S. state of Arkansas in the area known as the Arkansas Delta, that extends west of the Mississippi River. As of the 2010 census, the population was 77,435. Its county seat and largest city is Pine Bluff. Jefferson County is Arkansas's 21st county, formed on November 2, 1829, from portions of Arkansas and Pulaski counties, and named for Thomas Jefferson, third President of the United States.
The city and county of Denver is the second largest county by population, home to 600,158 people as of the 2010 U.S. census. It is followed by Arapahoe County, with 572,003 people; Jefferson County, with 534,543 people; and Adams county, with 441,603 people. The smallest county by population is San Juan County, with a population of 699.