2Features that determine the future of a population: Population size- the # of individuals in a populationPopulation density- the # of individuals in a given areaDispersion-the way individuals are arranged in space
20Modeling Population growth Population success = reproduction of speciesWe can study how and why the number of individuals change over timePopulations grow when more individuals are born than die in a given period. A simple population model describes the growth rate as shown:(r) = birthrate – death rate
21Describe what is happening to the population in this graph AGE# of IndividualsA small # of theyoungest-decreaseMiddle age populationis constant, secure,not changingThe older populationdecreases, faster
22Exponential GrowthExponential growth-the rate of population growth stays the same and the population size increases steadily.This model displays a J-shaped curve which indicates a steady increase of population size.
23What if the population size kept growing and growing and... carrying capacity (K)- the population size that an environment can sustainWhat factors do you think contribute to an environment's carrying capacity???
27LOGISTIC GROWTH MODELOnce again, exponential growth is a steady increase in the population size.Now we must consider the carrying capacity (K) and density-dependent factors when modeling population growth.logistic model- a population model in which exponential growth is limited by a density-dependent factor. This model considers carrying capacity.
31Remember...(r)= rate of growth, birthrate – death rate(K)= carrying capacity, the population size an environment can sustainThere are 2 types of populations,(r)-strategists and (K)-strategists
32r-strategist: Species that grow exponentially when the environment allows for it. Results in temporarily large populations.When the environmental conditions are no longer suitable for the species, the population size quickly decreases.
33K- strategists- organisms that grow slowly K- strategists- organisms that grow slowly. Population sizes are usually small and kept near the carrying capacity of their environment.K-strategists are characterized by a long life span, a slow maturing process, and reproduction late in life.