Announcements Lichen Lab is due next week

Examples of Logistic Growth Ex. fur seal population, St. Paul Island, AK Ex. Paramecium http://www.bio.miami.edu/dana/pix/logisticpopns.gif

The maximum number of individuals the environment can support is called Density determinant Carrying Capacity Saturation Maximum limit

Why do these populations level off as opposed to experiencing exponential growth? Limits of the environment – food, water, space etc

Three patterns of population growth: Exponential Logistic Overshoot Oscillations Crash and Burn Models – ‘ideal’

Overshoot with Oscillations Growth is so rapid the pop exceeds K Pop declines and recovers Cycles around K Ex. Moose on Isle Royale in Lake Superior

Overshoot with Crash & Burn Often occurs when a pop experiencing exponential growth runs out of resources Ex. Caribou on St. Matthew's Island

Ex. Caribou on St. Matthew's Island 29 introduced in 1944 1980 Extinct For a sense of how fast they grew 1944: 29 indivs. arrive 1956: pop size = 1,350 1963: pop size = 6,000 1966: pop size = 44 1980 Extinct

Reproductive Strategies r-selected species K-selected species What does the names tell us about how they might reproduce?

r-selected species Grow very rapidly Named due to high r Massive # of offspring Little to no parenting Short life span Small size

K-selected species More likely for pop to be close to K Fewer offspring Care for young Longer lived Larger size

B. History of Human Population Growth

6.87 billion people 1800s – 1 billion people

What type of growth does the prior graph show? Explosive Exponential Logistic Chaotic

The # of people the earth can support depends on (K) Technology Resource use Earth’s productivity Ex. More food from land

History of Human Population Growth Hunter-gatherers Agricultural Revolution Industrial Revolution

Hunter-gatherer Society Existed for most of human history World pop = a few million People move in search of food

People move in search of food No permanent shelter Low birth rate, low death rate → Stable pop. size

Agricultural Revolution 10,000 yrs ago people began growing crops People stay in one place and have larger families b increases

People stay in one place and have larger families b increases More food and better shelter d decreases Still diseases and sanitation problems Population increases

Population increases

Industrial Societies Industrial Revolution – 200 yrs ago Death rate decreases Birth rate decreases

Death rate decreases Technology: Medicine, sanitation, agriculture

Birth rate decreases High birth rate → low birth rate Doesn’t occur immediately

Initially, population increases rapidly and then becomes stable