Population Ecology: Growth & Dynamics

• Population ecology studies populations and their interactions with the environment.
• The environment impacts a population's density, distribution, age structure, and size.
• The environment limits population growth due to finite natural resources.
• Environmental supporting capacity affects population fluctuations.
• A population comprises individuals of a single species in the same area, likely to interbreed.
• Population density is the number of individuals per unit area or volume.
• Population increases through birth and immigration and decreases through death and emigration.
• Population grows when the birth rate exceeds the death rate.
• Population declines when the death rate exceeds the birth rate.

Exponential & Logistic Growth

• Exponential growth happens under optimal conditions with plentiful resources, producing a J-shaped curve.
• Logistic growth occurs initially, then slows, causing the population size to level off.

Factors Affecting Population Dynamics

• Resource abundance is the availability of environmental resources like food, water, and space.
• Life-history patterns include reproductive patterns.
• r-selection species are small, reproduce early, are mobile, and have short lifespans (e.g., mosquitoes).
• K-selection species are larger, have long lifespans, reproduce later, and have few offspring (e.g., mammals).
• Environmental conditions like seasons, climate, water, and light affect populations.
• Organism interactions limit population sizes below environmental capacity.
• r-selected traits: high reproductive rate, many offspring, low offspring investment, high offspring mortality, short lifespan, fast growth, quantity over quality, unstable environments, boom and bust cycles.
• K-selected traits: low reproductive rate, few offspring, high offspring investment, low offspring mortality, long lifespan, slow growth, quality over quantity, stable environments, stable population sizes.

World Population Milestones

• Neolithic Revolution occurred around 10,000 BCE.
• Development of technology facilitated planting, harvesting crops, and animal domestication.
• Agriculture provided a more abundant and reliable food supply, supporting population growth.
• The Neolithic Revolution transitioned nomadic hunter-gatherers to settled agriculture.
• This era involved domesticating plants and animals.
• Permanent settlements as villages that later became cities were developed.
• Key impact: increased food production and population growth.
• Key impact: specialized labor and social hierarchies developed.
• Key impact: new technologies like pottery and weaving emerged.
• The Neolithic Revolution was foundational for civilizations and complex societies.
• The Industrial Revolution occurred roughly from 1760-1840.
• Man harnessed fossil fuels (coal, oil, natural gas) as a high-capacity energy source.
• Supply of food, raw, and processed materials improved, along with trade and transportation.
• A booming economy supported by surplus energy supported human population growth.
• Industrialization was initially staggered a population of a half million to a billion in 200 years.
• Major technological advances occurred in Great Britain, driven by new energy sources such as coal.
• Mass production, factory systems, and urbanization occurred.
• There was unprecedented economic growth and increased standards of living for some.
• Mass migration from rural areas to cities occurred.
• New social classes (industrial working class and capitalists) rose.
• Environmental pollution and resource depletion occurred.
• Globalization and increased interconnectedness.
• The Medical Revolution occurred approximately from 1870-1950.
• The discovery of infection causes and transmission led to major treatment changes.
• Improvements in public sanitation and personal hygiene occurred.
• The human population was liberated from infectious diseases while maintaining a high birth rate.
• Key impact: exponential rise of population happened during this time.
• Rapid progress in medicine occurred, including the development of germ theory.
• Antibiotics, vaccines, and improved sanitation were developed.
• Dramatic decline in infectious diseases and mortality rates occurred.
• Increased life expectancy occurred.
• Public health and hygiene improved.
• Growth of the modern healthcare system occurred.
• The Green Revolution occurred from 1940s-1960s.
• There was an attempt to increase agricultural systems' production and efficiency globally.
• New technologies were developed as a solution for worldwide starvation.
• Research and technology initiatives increased agricultural production worldwide, particularly in developing countries.
• High-yielding crop varieties were developed.
• Increased fertilizer and pesticide use occurred.
• Improved irrigation techniques were also developed.
• A significant increase in food production occurred aiding in averting famines.
• Transformation of agricultural practices occurred.
• Increased use of chemical inputs took place.
• There are potential environmental consequences.
• There are concerns about the loss of biodiversity and the sustainability of intensive agriculture.
• The Environmental Revolution is ongoing.
• Proactive switching from unsustainable practices to efficient and clean "green” technology.
• Environmentally sustainable energy sources are being shifted to.
• New methods of farming and agriculture are being developed.
• Energy-efficient technologies are being created.
• Better urban and regional planning and policy changes are being made.
• There is growing movement, a shift in consciousness towards environmental sustainability.
• Interconnectedness of human society and the natural world is recognized.
• Key impacts: Development of renewable energy technologies.
• Key impacts: Increased awareness of environmental issues.
• Key impacts: Shift towards sustainable practices in various sectors.
• Systemic change is being pressed moving to address root causes of environmental problems.