Understanding Populations Chapter 8

Population: set of individuals within a species living in the same place at the same time. -Described in terms of size, density, and dispersion. -Size = total number of individuals -Density= number if individuals per unit area of volume -Dispersion = arrangement of individuals in space (even, clumped, or random) -Population growth : change in pop = births - deaths -Reproductive potential: maximum number of offspring that each member of the population can produce.

Exponential growth: populations doubles. 2 then 4 then 8 then 16 etc… -J shaped curve on a graph Carrying capacity: maximum population that its ecosystem can support indefinitely. - S shaped graph with waves.

Growth rate = change in population / time Density dependent: deaths occur more quickly in a crowded population. Density independent: certain populations die regardless of the population. Niche: a role an organism plays in a system, range of conditions in which a species can survive

How species interact with each other Competition: when different organisms attempt to make use of the same resource. Commensalism: one species benefits and the other species is neither helped or harmed. example: remoras and sharks Parasitism: one species benefits at the expense of the other (the host, and usually doesn’t purposely kill it) examples: fleas, ticks, tapeworms Mutualism: both species benefit from the relationship example: clown fish and anemones. Symbiosis: relationship when two species live in close association with each other.