Limits to Growth Human Population Growth 5-2 and 5-3

Population Growth Is Limited Limiting Factor: factor that causes population growth to decrease 2 kinds of limiting factors 1.Density-Dependent Factors: depends on populations size 2.Density-Independent Factors: affect all populations in similar ways, regardless of size

Density Dependent Limiting Factors Density: the number of organisms per unit area 1.Competition 2.Predation 3.Parasitism 4.Disease Be able to explain why these factors are present in crowded populations (hi-density populations)

Predator-Prey Relationship Explain the diagram below:

Density Independent Limiting Factor Affects all populations in the same way, regardless of size 1. Unusual weather 2. Natural disasters 3. Human activities 4. Seasonal cycles Can you give an example for each listed above?

Human Populations In history, human population remained constant (no growth or decline) High birth rate and high death rate

Population Growth Goes Exponential! 500 years ago, human population began to explode… –Agriculture –Industry –Medicine –Improved Sanitation –Healthcare This drastically reduced the death rate, but didn’t change birth rate

Modeling Growth Demography: Scientific study of human populations Observation: US, Japan, Europe growth slows Experiment: collect data (US Census) Model: “Demographic Transition” Hypothesis

Demographic Transition :A dramatic change in birth rate and death rate Stage 1: High birthrate and high death rate –Most countries in early history Stage 2: High birthrate and low death rate –US ( ), developing countries Stage 3: Low birthrate and low death rate –US (now), Europe, and Japan

Age Structure Diagrams Population profiles to predict future growth STABLE RAPID GROWTH DECLINE

Growing populations

Not growing

Check yourself What type of growth does each graph show?

Explain this age structure diagram