Chapter 5 Populations Section 5.1 How Populations Grow Section 5.2 Limits to Growth Section 5.3 Human Population Growth

Section 4.1 Population Dynamics Compare & contrast exponential and linear population growth. Relate the reproductive patterns of different populations of organisms to models of population growth. Predict effects of environmental factors on population growth

What is a Population? One species spread over it geographic range (all areas it lives) Density # in population within the geographic range 3 types: Random Uniform Clumped

Population Growth Growth Rate is effected by several factors: Age Structure number of males/females and their ages Birthrate number of babies born a year Death rate number of deaths a year Immigration members entering the range Emigration members leaving the area

Types of Population Growth J-shape growth Exponential Growth: As a population gets larger, it also grows at a faster rate Always the growth rate after a succession or a new species is introduced

Type of Population Growth S-shape growth Logistic Growth: After exponential growth slows down as resources become limited Growth flattens out at maximum possible population size (carrying capacity)

Limits to Growth Carrying capacity The number of organisms of one species that an environment can support indefinitely is its carrying capacity When a population overshoots the carrying capacity, then limiting factors may come into effect

Limits to Growth Limiting Factor any factor that limits a populations size Food, predators, space, water, etc.. 2 Types: Density-Dependent Increase/decrease with population’s size Density-Independent Size of population has no affect

Density-Dependent Limiting Factors Competition More members the more food/water that is required Kills off weaker members Predation Prey and Predator numbers are effected by each other Overcrowding Stress of crowds weakens immune systems and increases fighting Parasitism and Disease Overcrowding spreads disease faster

Density-Independent Limiting Factors Weather Patterns Ruin food supply Run out of fresh water Limit time to hunt/reproduce Natural Disasters Massive lowering of population numbers Change the ecosystem Remove important food supply

Human Population Growth Human’s used to have a very high birthrate but also a very high death rate Today the birthrate is 4 babies a second but the death rate is much lower What factors lowered our death rate? Food supply, medicine, civilization, etc…

Demographic Transition Demography study of human populations Periods of Growth: High birth and death rates in unstable environments Lowering of death rates as environment becomes more stable Birthrates fall to meet death rates as resources become limited

Age Structure’s Effects on Growth Populations with high numbers teens and young adults will lead to fast massive growth Large number in the older generation will have slower growth Most stable growth is having near even numbers in all age groups

Homework! Read Ch. 6; You have another presentation coming up Ch. 6 vocabulary Ch. 5 “Apply Vocab” and questions #1-16 on p. 123-124