part 2 - February 17, 2005 Slide Show 5 Credation,...

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February 17, 2005 Slide Show 5 Credation, competition, availability of food, climate…are the four factors on population Competition between species that compete for the same resource (food) Paramecium. ..only 1 species survived. ..but in reality, both usually survive Some birds change their food habits and bill structure to compete with other species Human populations: Major events in history of life have changed…50 years ago it was about 2 bya that the earth formed, now it is 4.5 bya… The last ice age ended about 12k years ago and agriculture started about 10k years ago in Iran, Peru, and New Guinea Population increase: see lecture 5 slide 46 People think carrying capacity of world is 10 billion, some even think 50 billion, but who wants to live in that world Before, increase in population was always good for economy, however, now there are many more negatives…some countries have decreasing populations (Europe). --farmers usually have lots of children to have a good labor force to maintain crops --in India, you should attempt to have a male child, because the oldest male child is supposed to take care of the parents as they age --smaller populations prevent these from happening If a population increases, total habitat destruction and fragmentation (fragmenting the original habitat) --lower health --loss of individual freedom, more controlled Ideal size for a city…500k Ideal size for world…2 billion (way beyond that already) Robert Thomas Malphus in 1800s—saw that human population was following a logistic growth curve that would keep growing at a dramatic rate, peak, and then crash 5 things people are concerned with about population change: Abundance of humans Birth rates Death rates Age structure Growth rate --also see lec 5 slide 50 for equation: P2=P1 + (births – deaths) + (immigration – emigration) --doubling rate is 70/annual growth rate % 1
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*Infant mortality rate and a pre reproductive mortality rate. (there are some eggs produced that don’t survive) These decrease the population. *We also have more men in the world than women. Many more males born in war time than females. *Life expectancy during hunting and gathering times was about 40 years. They gauged this by looking at teeth and skulls found. In ancient rome, BC area, 1 year olds would live until about 22 years old. But if you survived until 75 years old, you would probably survive until 90 years old. People believe that pollution has contributed to decreasing life expectancies. In the year 1900 in the US the life exp. was 47 years… in ’77, it was ??? NOW: 87 years. IE: life expectancies increasing. CAUSES FOR POPULATION DECREASE 1) Disease . ( black death due to bubonic plague carried by fleas was pandemic— worldwide—between 1346 & 1350, 25% of Europeans died. Recent threats about disease are terrorist threats like anthrax, smallpox virus, chicken flu in SE Asia, etc.) 2) Starvation : Reasons can be political like in Africa. Massive starvation occurring. 3)
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part 2 - February 17, 2005 Slide Show 5 Credation,...

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