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 Growth Video 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
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 the other 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”
Thomas Malthus British 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.