NOTES Ch 15 #3 2/13 POPULATION STUDIES

When animals first inhabit an area, there are only a few males and females. They have offspring..those grow up …they have offspring, etc. Happens very slow at first. LAG PHASE – period of slow grow in a population

Soon, a lot of offspring are having offspring and population begins to double EXPONENTIAL PHASE – period of very rapid growth in a population. EX: 200 birds now 400 birds – next year 800 birds – next year

WHAT CAN CAUSE EXPONENTIAL GROWTH? When there is new space or habitat for them new food supply available predators decrease or gone

J - CURVE LAG EXPONENTIAL

The environment cannot provide enough for a population to grow exponentially forever. It will reach its CARRYING CAPACITY – the maximum number of individuals that the environment can support.

STABILIZATION PHASE – period when a population steadies because its carrying capacity is reached. Number or births = death No change in population size

S - CURVE CARRYING CAPACITY LAG EXPONENTIAL STABILIZATION

LIMITING FACTORS Things in the environment that stabilize population size and keep species from unlimited growth EX: CHOSE 5 space Food amount of sunlight (plants) Oxygen in water (fish) Soil nutrients (plants) Temperature Nesting materials (birds) Diseases Parasites Natural disasters Predators

VIDEO: MYSTERY OF EASTER ISLAND

HUMAN POPULATION 10,000 BC = 3 million people Slowly grew (lag phase) until = 1 billion 1930 = 2 billion 1975 = 4 billion 2008 = 6.8 billion Rapids growth - exponential phase

Human population still in exponential phase.

Why the increase? * medicine * agricultural advances * better food storage and distribution

PROBLEMS Increasing population causes increased competition….the earth needs to provide for all these people Soon, it will reach its carrying capacity and population will stop growing. There will not be enough resources to support more people. This will increase competition more.

In 1999, reached 6 billion people. *We are still in exponential phase. The growth rate is 250,000 new people a year. At this rate, population will double every 40 years. (2013 = 8 billion)