Population Growth Ellsworth 2015

What is a population? A population is a group of individuals of the same species living in the same geographic area. Population Dynamics The study of factors that affect growth, stability, and decline of populations is population dynamics.

What 3 phases do populations go through? All populations undergo three distinct phases of their life cycle: growth stability decline

What is meant by population growth? Population growth occurs when available resources exceed the number of individuals able to exploit them. Reproduction is rapid Death rates are low Immigration Occurs Growth is experience when rapid reproduction, immigration and low death rates combine to produce a net increase in the population size.

What is population stability? Population stability is represented when a population is not experiencing rapid growth or great decreases over long periods of time. Stability is experienced when fluctuations in populations stay within an average count range despite minor disturbances over long periods of time.

What is population decline? Decline is the decrease in the number of individuals in a population, and eventually leads to population extinction. Decline is experienced when decreases in population are greater than increases.

4 Factors that influence population growth rate Birth Rate Death Rate Immigration Emigration

Birth Rate The proportion of births to the total  population in a place in a given time, usually expressed as a quantity  per 1000 of population.

Death Rate The number of deaths per unit, usually 1000, of population in a given place and time.

Immigration The movement of individuals into an area in order to settle there

Movement of individuals out of an area. Emigration Movement of individuals out of an area.

4 Social Factors Four social factors that influence human populations: Birthrates Death rates Age-Structure Limiting Factors

Age-Structure Another characteristic of populations that ecologists measure is population age structure. This characteristic is as simple as it sounds: it’s a summary of the number of individuals of each age in the population. Age structure is useful in understanding and predicting population growth.

Population Pyramid Shows Age-Structure

Limiting Factors Any biotic or abiotic factor that restricts the numbers, reproduction or distribution of organisms. Examples Food Supply Water Supply Predators Shelter Prey Space

Carrying Capacity The maximum sustainable size of a resident population in a given ecosystem.

Modes of population growth

Exponential & Logistic Growth

Human population growth over the past 10,000 years

Two modes of population growth The Exponential curve (also known as a J-curve) occurs when there is no limit to population size. The Logistic curve (also known as an S-curve) shows the effect of a limiting factor (in this case the carrying capacity of the environment).

Human Population Near 1650, the slow population rate increases exponentially for humans. Annual growth rate reached its peak in the late 1960s, when it was at 2% and above. Population in the world is currently (as of 2015-2016) growing at a rate of around 1.13% per year.

Human Population New technologies for medical care, hunting and farming have enabled this rapid increase. It took over 100,000 years to reach a total population of 1 billion, but only 123 years to reach 2 billion, and a mere 33 years to reach 3billion.

Human Population The annual human growth rate is currently declining and is projected to continue to decline in the coming years. Replacement–Birthrate The level of fertility at which a couple has only enough children to replace themselves, or about two children per couple.

Human Population Replacement Birthrate for developed countries is 2.1%. 2.33 for the world and much higher for developing countries. Birthrate for USA for 2014 is 1.97%. Birthrate for Japan for 2014 is 1.41% Birthrate for Niger for 2014 is 7.58%

Human Population Previous Milestones 1 Billion: 1804 Over 100,000 years 2 Billion: 1927 123 years 3 Billion: 1960 33 years 4 Billion: 1974 14 years 5 Billion: 1987 13 years 6 Billion: 1999 12 years 7 Billion: 2012 13 years

World Population http://www.worldometers.info/world-population/#growthrate http://www.worldometers.info/world-population/population-by-country/ http://www.worldometers.info/world-population/world-population-gender-age.php https://www.cia.gov/library/publications/the-world-factbook/rankorder/2127rank.html

Arizona Populations Arizona State 6.7 Million as 2014 Phoenix: 1,445,632 Tempe: 161,719 Tucson: 520,116 Peoria: 154,065 Mesa: 439,041 Surprise: 117,517 Chandler: 236,123 Yuma: 93,064 Glendale: 226,721 Avondale: 76,238 Scottsdale:217,385 Flagstaff: 65,870 Gilbert: 208,453 Goodyear: 65,275