Limits to growth Chapter 5.2

Limits to Growth A factor that causes a population to decrease Limiting Factor 2 types: Density-dependent Limiting Factor Density-independent Limiting Factor A factor that causes a population to decrease Population size matters Not effected by population size

Density-dependent Limiting Factors Limiting when the population density reaches a certain level. Examples: Competition Predation Parasitism and Disease - food, space, water, sunlight - Eating of other organisms - Cause death

Predator-Prey Relationships As prey #’s increase the predator #’s increase shortly after - More food Then increase in predators causes decrease in prey populations – More hunters

Predator – Lynx Prey - Hare

Density-Independent Limiting Factor Affect populations regardless of population size. Examples: Natural Disasters Unusual Weather Seasonal Cycles Human Activities -Hurricanes & fires -Droughts & extreme temps - Excessive Rain & Seasonal frosts -Damning Rivers & cutting forests

PREDATOR PREY RELATIONSHIPS

POPULATION CYCLES

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Human Population Growth Chapter 5-3

History 1. Human population is increasing with time (like many other organisms). 2. About 11,000 years of human existence- population growth was slow. Reasons: a. Food was scarce b. Disease c. ½ the children survived to adulthood

3. Industrial Revolution changed human growth rate/longevity. a 3. Industrial Revolution changed human growth rate/longevity. a. Food was more plentiful b. Improved sanitation, medicine, nutrition

Figure 5-10

B. Patterns of Population Growth 1 B. Patterns of Population Growth 1. Demography- study of human populations a. examines characteristics of human populations b. explains how populations change over time 2. Birthrate, death rate, and age structure of a population help predict why some countries have high growth rates while other countries grow more slowly

Figure 5-12 Draw on back of notes 3. Demographic Transition- a dramatic change in birth and death rate a. Birthrates/deathrates- high Deathrates drop/birthrate remains high. Birthrate then drops b. Has occurred in U.S., Europe and Japan- rest of the world still growing

4. Age-Structure Diagram- Population profile a 4. Age-Structure Diagram- Population profile a. Graphs of number of people in different age groups b. Shows percentages of males and females in the populations

Figure 5-13

C. Future Population Growth 1 C. Future Population Growth 1. Predicts how the world population will grow 2. Must consider a. age-structure b. prevalence of disease 3. Current projections-that by 2050 population may reach 9-12 billion.

What’s Behind the Human Population Explosion? • Three Factors Fertility Infant Mortality Longevity Animal Domestication and Agriculture Provided for a few to feed many Industrial Revolution Growth of Cities and Infrastructure Water Energy Transportation Increased Productivity Nutrition Sanitation Medicine

How are humans affecting the environment? Limited Resources – Land, food, water Agriculture Industries Ecosystem Goods Renewable Nonrenewable Desertification & Deforestation • Water pollution • Biological magnification • Air pollution • Acid rain • Habitat Fragmentation • Introduced Species  What is the size of YOUR ecological footprint?

Human Population Growth