WEEK 3.1 LESSON - Understanding Growth and Change.pptx

WEEK 3.1 LESSON - Understanding Growth and Change

1. Population Ecology: Understanding Growth and Change Week 4 Lesson

2. What is Population Ecology? Population ecology is the study of how and why populations change in size, density, and distribution over time . It examines: The dynamics that affect group sizes of organisms Interactions within and between populations How populations respond to environmental changes Mathematical models that predict population trends

3. Four Factors Driving Population Change Natality (Birth) Addition of new individuals through reproduction Influenced by fertility rates Age of sexual maturity Reproductive strategies Mortality (Death) Loss of individuals from the population Lifespan and aging Predation and disease Environmental stressors Immigration Movement of individuals into a population Resource availability Habitat quality Population pressure elsewhere Emigration Movement of individuals out of a population Overcrowding Resource depletion Environmental changes

4. Human Population Growth: A Brief History 10 000 BCE: Pre-agricultural nomadic groups Agricultural Revolution: Stable food sources enabled larger, sedentary populations Industrial and Medical Revolution: A dramatic decline in death rates while birth rates remained high 20 th -21 st Century Milestone 1B(1804) 2B(1927) 4B(1974) 8B(2022)

5. Pre-Agricultural Nomadic Groups Existed before the development of farming (over 10,000 years ago). Small population size, usually fewer than 100 people per group. Depended on hunting, fishing, and gathering wild plants for survival. Nomadic lifestyle – moved frequently to follow food sources and seasonal resources. Population growth was slow and limited due to high infant mortality, diseases, and food scarcity. Life expectancy was low, often less than 30 years. No permanent settlements; lived in temporary shelters such as caves, tents, or huts. Social structure was simple, often based on kinship and cooperation. Birth rates were balanced by high death rates, keeping populations stable.

6. Agricultural Revolution (about 10,000 years ago) Marked the shift from hunting and gathering to farming and the domestication of animals . Humans began to settle in permanent villages , leading to larger and more stable populations. Reliable food supply reduced the risk of famine and increased survival rates. Birth rates remained high while death rates began to decline → faster population growth . Led to advances in tools, irrigation, and crop cultivation . Populations became more concentrated, forming the first towns and civilizations . However, dense settlements also increased exposure to disease outbreaks .

7. Industrial Revolution (1700s–1800s) Shift to mechanization, factories, and new technologies Major increase in food production and efficiency Growth of cities due to urban migration Improved transportation and trade Death rates declined while birth rates stayed high Resulted in rapid population growth Medical Revolution (1800s–1900s, continuing today) Advances in medicine, vaccines, and antibiotics Better public health, sanitation, and clean water Infant mortality rates decreased Life expectancy increased significantly Spread to developing countries, boosting growth Fueled exponential population increase

8. 20th–21st Century Milestones Global population exploded from ~1.6 billion (1900) to over 8 billion (2023) . Driven by the Industrial and Medical Revolutions : vaccines, antibiotics, sanitation, and improved nutrition. Death rates dropped sharply , while birth rates remained relatively high in many regions. Green Revolution (1940s–1960s): major advances in agriculture boosted food production, supporting rapid growth. Developed countries: population growth slowed due to lower fertility rates and family planning.

9. Developing countries: population growth remained fast , creating demographic imbalance. Growth became exponential , raising concerns about carrying capacity and resource use. Increasing urbanization : more than half of the world’s population now lives in cities. Major issues: climate change, resource depletion, inequality, and sustainability challenges . Today, population growth is slowing overall , but global distribution is uneven (Africa & South Asia still growing rapidly).

10. Exponential Growth: Reaching 8 Billion It took all of human history until 1804 to reach 1 billion people, but only: 123 years to add the second billion (1927) 33 years to add the third billion (1960) 14 years to add the fourth billion (1974) 13 years to add the fifth billion (1987) 12 years to add the sixth billion (1999) 12 years to add the seventh billion (2011) 11 years to add the eighth billion (2022) Current growth rate: ~80 million people per year

11. Malthusian Theory (1798) "Population increases geometrically while food production increases arithmetically." Malthus predicted that population growth would inevitably outpace food production, leading to widespread famine, disease, and conflict—unless checked by "moral restraint" or "misery and vice." Was Malthus Wrong? Factors Malthus didn't anticipate: Agricultural technology advances (Green Revolution) Demographic transition model Declining fertility rates with development Contraception and family planning

12. Demographic Differences: Developed vs. Developing Nations Infant Mortality Rate Highly Developed: 3-6 deaths per 1,000 live births Developing: 30-60+ deaths per 1,000 live births Reflects healthcare quality, sanitation, and maternal nutrition Total Fertility Rate (TFR) Highly Developed: 1.2-1.8 children per woman Developing: 2.5-5.0+ children per woman Influenced by education, women's empowerment, and economic needs

13. Demographic Differences: Developed vs. Developing Nations Replacement-Level Fertility Highly Developed: Below replacement (2.1) Developing: Often well above replacement Determines if population will grow, stabilize, or decline long-term Age Structure Highly Developed: Aging populations, "inverted pyramids" Developing: Youth-dominated, broad-based pyramids Influences dependency ratios and future growth potential

14. Challenges of Rapid Urban Growth Overcrowding and Housing Shortages Rapid population growth in cities often outpaces the availability of housing. Leads to the development of slums, squatter settlements, and informal housing . Families may live in cramped, unsafe, and unsanitary conditions . Overcrowding increases stress on social services and lowers quality of life.

15. Challenges of Rapid Urban Growth 2. Pollution (Air, Water, Waste Management) Increased number of vehicles and industries leads to air pollution . Poor sanitation and lack of clean water sources contribute to water pollution . Improper waste disposal causes garbage accumulation and health risks. Pollution harms both the environment and human health in urban areas.

16. Challenges of Rapid Urban Growth 3. Strain on Infrastructure (Transportation, Electricity, Water Supply) Existing infrastructure often cannot keep up with rising demand. Traffic congestion and insufficient public transport reduce mobility. Electricity shortages and water scarcity affect daily living conditions. Infrastructure failures lead to inefficiency and reduced economic productivity.

17. Challenges of Rapid Urban Growth 4. Increased Unemployment and Poverty Large influx of people into cities creates job competition . Not enough employment opportunities, especially for unskilled workers. Leads to poverty, informal work, and reliance on low-paying jobs . Widening gap between rich and poor increases social inequality.

18. Challenges of Rapid Urban Growth 5. Public Health Challenges Overcrowding and poor sanitation increase spread of infectious diseases . Limited access to healthcare services strains hospitals and clinics. Air and water pollution contribute to respiratory and waterborne illnesses . Malnutrition and mental health issues are more common in underserved populations.

19. Population ecology helps us understand growth patterns and challenges Four key factors determine population changes Human population has grown rapidly through history, with ongoing debates on sustainability Developed and developing countries face different demographic challenges Rapid urbanization brings significant social and environmental problems LET’S SUM UP!