POPULATION DENSITY NUMBER OF INDIVIDUALS PER UNIT AREA

POPULATION CHARACTERISTICS § Geographic distribution § Density § Growth rate § Age Structure

POPULATION GROWTH § Number of births Ø Birth rate>Death rate (increase) Ø Birth rate=Death rate (same size) § Number of deaths Ø Birth rate<Death rate (decrease) § Number of individuals entering (immigration) and leaving (emigration) population

WORLD BIRTH/DEATH RATES § Which continent is having greatest population growth? § What is the population growth rate of the United States? § Correlation between birth and death rates in particular parts of the world

COMPARING BIRTH/DEATH RATES § Developing countries have high birth rates § High birth rate: Expectation that some will die because of the high infant mortality rate § Help in looking after the farm § Care for parents if they become old or sick; there may not be a old age pension scheme § Shortage of family planning facilities and advice

COMPARING BIRTH/DEATH RATES § Developed countries have low birth rates § Expensive to look after large families § More women prefer to concentrate on careers § Women have more control over their own fertility § Ready availability of contraception and family planning advice

EXPONENTIAL GROWTH § Reproduction of a population at a constant rate § Initial slow growth § Exponential growth would continue under ideal conditions with unlimited resources § Bacteria colony growth J CURVE

LOGISTIC GROWTH § Growth slows/stops following a period of exponential growth § Graph is S-shaped § Point of graph where it levels off (roughly zero growth) is the carrying capacity (largest number of individuals environment can support)

THINK TANK § 1200 penguins at beginning of year 1600 penguins at end of year WHAT WAS POPULATION GROWTH? § During year 250 penguin chicks died WHAT WAS POPULATION GROWTH? § During same year, 220 adults died WHAT WAS POPULATION GROWTH?

THINK TANK § Define and/or describe how the following factors affect the size of a population: birth rate): b. mortality (= death rate): c. growth rate: d. immigration: e. emigration: Briefly describe exponential growth and what it looks like when graphed. §Briefly describe logistic growth, and what it looks like when graphed. Define carrying capacity and describe how it affects logistic growth

LIMITS TO GROWTH § Factors that cause population growth to decrease § Density-dependent factors --competition --predation --parasitism --Disease

Density-Dependent Factors § Strongly affect a large, dense population, NOT small, scattered populations as greatly § Competition --food/water --space --sunlight § Larger populations use up available resources faster than smaller ones

Density-Dependent Factors § Predation § Prey population decreases over time § Predator decline will soon follow § Lag time between decline an rise

Density-Dependent Factor § Parasitism-Disease

Density-Independent Factors § Affect all populations in similar ways, regardless of size § Unusual weather, natural disasters, seasonal cycles, human activities

THINK TANK § Identify as density-dependent or densityindependent: --flood --lack of food source --clear cutting forests --predation --parasitism

Human Population Growth § Demography: scientific study of human populations § Age Structure Diagrams: Show population by age and gender groups

THINK TANK § Why might a contagious virus that causes a fatal disease be considered a density-dependent limiting factor? § Using the age-structure, describe the population demographic transition of Sweden.