• 3 important characteristics of a population are its geographic distribution, density, & growth rate.
• Geographic distribution, or range, is a term that describes the area inhabited by a population.
• The range can vary in size from a few cubic centimeters, occupied by bacteria in a rotting apple, to the millions of square kilometers occupied by migrating whales in the Pacific Ocean.
• Population Density is the number of individuals per unit area.
• This number can very tremendously depending on the species and its ecosystem.
• 3 factors can affect population size: 1)# of births, 2)# of deaths, 3)# of individuals that enter or leave a population.
• Populations will grow if more individuals are born than die in any period of time.
• A population will grow if its birth rate is greater than its death rate.
• Birth rate = death rate, the population will more or less stay the same size.
• Immigration-movement of individuals into an area, another factor that can cause a population to grow.
• Emigration-movement of individuals out of an area, can cause a population to decrease.
• If a population has abundant space and food, and is protected from predators and disease, then organisms in that population will multiply and the population size will increase.
• Exponential growth-occurs when the individuals in a population reproduce at a constant rate.
• At 1st the number of individuals will increase slowly, but over time the population becomes larger and larger until it reaches an infinitely large size.
• Under ideal conditions with unlimited resources, a population will grow exponentially.
• The shape of a curve in an exponential growth graph is a J.
• As resources become less available, the growth of a population slows or stops.
• The S-shaped curve of this growth pattern, is called logistic growth.
• Logistic growth-occurs when a population’s growth stops or slows following a period of exponential growth.
• Population growth may slow down when the...