POPULATION DENSITY NUMBER OF INDIVIDUALS PER UNIT AREA

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

POPULATION GROWTH  Number of births  Birth rate>Death rate (increase)  Birth rate=Death rate (same size)  Number of deaths  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 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 --competition --predation --predation --parasitism --parasitism --Disease --Disease

Density-Dependent Factors  Strongly affect a large, dense population, NOT small, scattered populations as greatly  Competition --food/water --food/water --space --space --sunlight --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 density- independent: --flood --flood --lack of food source --lack of food source --clear cutting forests --clear cutting forests --predation --predation --parasitism --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.