Start-Up If there are 50 alligators in a swamp that measures 10 km2, what is the alligator’s population density?

Population Growth

There are currently 6,819,500,000 people on the planet and 319,213,000 in the US.

-US Census Bureus,

How many people have been added during this class period? Remind me to come back at the end.Population Ticker

History of Human Population GrowthVideo Questions:

1. What events led to an increase in population?

2. What events led to a decrease in population?

Population Growth

The size of a population is the result of a balance between two

major opposing forces:

1. Biotic potential - max rate population could increase

assuming ideal conditions

2. Environmental resistance: limits to growth determined

by biotic and abiotic

factors such as

-availability of food & space-competition-predation-climate

Exponential growth

Limitations on growth (environmental resistance) lead to a:

carrying capacity – maximum number of individuals in a population that the environment can support

Population Cycles

-population growth is sometimes cyclic-boom and bust cycles-example: hare-lynx population cycle

Hare-Lynx population cycles

Competitive exclusion principle – 2 species with similar needs for the same limiting resource cannot coexist in the same place

Placed two Paramecium species in the same culture

P. aurelia

P. caudatum

One always drove theother to extinction!

Due to competitive exclusion, most species have evolved separate niches

Niche – an organism’s living place, food sources, time of day it is active – it’s “job”

HUMANPOPULATIONGROWTH

Human Population Growth

What type of growth does this look like?

Exponential Growth

© Clay Bennett

Thomas MalthusBritish economist (1766-1834)

In 1798, published On Population in which he made the prediction that population would outrun food supply, leading to famine, war, and the collapse of society.