Population Dynamics and Migration

Population Dynamics

• Population is the total number of organisms of the same species in a specific area at a given time
• Population ecology blends natural science, predictive modeling, and social sciences to study population changes

Estimating Population

• Demography focuses on the statistics of population change
• Natural growth rate is calculated as the number of births minus the number of deaths per 1000 individuals
• Immigration and emigration are key factors in population change

Migration Effects

• Migration can alter local ecosystems through food chains, webs, and niche dynamics, potentially causing boom and bust cycles
• Migration has effects like genetic and cultural shifts, competition, and the spread of disease
• Migration is linked to gentrification, economics, class divisions, and political issues

Reasons for Migration

• Populations migrate due to weather or climate, war, economic status, and political persecution
• Migration occurs in search of a better environment defined by superior living conditions and optimal abiotic plus biotic factors

Population Growth

• Total growth rate includes immigration and emigration
• Doubling time indicates how long it takes for a population to double in size

Population Characteristics

• Population size is the total number of individuals in a defined area
• Population density measures individuals per unit area or volume
• Sex ratio is the proportion of males to females
• Operational/functional sex ratio considers only reproductively available individuals

Population Factors

• Behavioral aspects influence population dynamics
• Age distribution is categorized into pre-reproductive, reproductive, and post-reproductive stages
• Biotic potential refers to the maximum reproductive capacity of a species under ideal conditions
• Fecundity is the potential number of offspring, while fertility is the actual number produced

Population Growth

• Carrying capacity is the maximum number of individuals an area can sustain over time
• Availability of energy sources is a key influence
• Waste accumulation, such as eutrophication, impacts carrying capacity
• Interspecies interactions affect population sizes
• Environmental resistance includes total environmental factors that limit population growth and restrict biotic potential

Reproductive Strategies and Population Growth

• K-strategists are larger species with long lifespans that produce fewer young, exhibit logistic growth and invest in parental care
• R-strategists species are smaller with short lifespans, produce many offspring, exhibit exponential growth, and invest little in parental care

Limits to Population Growth

• Density-dependent factors, such as predation, competition, waste accumulation, and diseases, intensify with population density, affecting K-strategists more
• Density-independent factors, such as weather extremes, natural disasters, and habitat destruction affect population size regardless of density, affecting r-strategists more

Survivorship and Demographic Transition

• Both density-dependent and density-independent factors interact
• Type I survivorship curve shows late loss (humans), Type II shows constant loss (birds), and Type III shows early loss (trees)
• Demographic Transition Theory explains population growth changes from pre-industrial high birth and death rates to post-industrial low rates

Demographic Transition Stages

• Stage 1 (Pre-Industrial) features high birth and death rates, leading to slow population growth
• Stage 2 (Transitional) sees declining death rates due to advances in healthcare, sanitation and food production, while birth rates remain high, causing rapid growth
• Stage 3 (Industrial) has declining birth rates because of contraception, urbanization, and changing norms, resulting in slower growth
• Stage 4 (Post-Industrial) has low birth and death rates, leading to stable or declining population

Environmental Problems

• Environmental Impact of Population (I) is determined by: Population (P) times Consumption per Person (Affluence, A) times Technological Impact per unit of consumption (T)

Energy Sources

• Fossil fuels account for 75-80% of global energy consumption and are non-renewable
• Alternative energy sources, including renewables, were discovered 1990s onwards

Fossil Fuels

• Fossil Fuels are the largest contributor of carbon emissions
• Crude oil, a liquid fossil fuel, is extracted from oil wells and used to make plastics
• Coal accounts for 12.4% of indigenous energy which is the most abundant
• Coal forms from dead plants in the biosphere converted by tectonic activity, heat, and pressure over millions of years

Characteristics of Coal

• Coal is non-renewable
• Coal occurs in seams and is extracted through stripmining, the shallowest and easiest mining method
• Coal has the largest environmental footprint
• Coal is cheap, accessible, and usable with existing technology
• Coal mining leaks heavy metals
• Coal combustion releases carbon emissions and high sulfur causing acid rain
• Coastal power plants using coal can harm local aquatic ecosystems with heated water

Natural Gas

• Natural gas is composed of mostly methane and extracted from wells
• Considered the “cleanest fossil fuel” but still contributes to combustion-related problems
• Transportation of natural gas has a large footprint

Alternative Energy

• Nuclear energy is a non-renewable source releasing a large amount of energy
• Hydropower is renewable, using tidal energy from dams but altering land

Geothermal and Wind Energy

• Geothermal energy relies on Earth's tectonic activity using geothermally heated steam
• Wind energy converts kinetic energy into electrical energy via turbines, but has a short lifespan and depends on weather
• Solar energy uses photovoltaic panels and is accessible, scalable, but weather-dependent
• Biofuels convert biomass into electricity

Atmosphere

• Climate change and global environmental problems require global compliance
• Major atmospheric gases include Nitrogen (78%), Oxygen (21%), Argon (0.9%), Carbon Dioxide (0.03%), and varying concentrations of Water Vapor
• Trace gases from combustion significantly pollute the atmosphere
• Troposphere is where humans live

Layers of the Atmosphere

• Most air pollution stays in the troposphere
• The surface reradiates as infrared, heating the surface and lower atmosphere
• Stratosphere contains the ozone layer absorbing UV rays
• The stratosphere moderates temperature, cooling the atmosphere
• Mesosphere is the coldest layer and protects from meteors
• Thermosphere is the hottest layer, containing charged particles that cause auroras
• Exosphere is the outermost layer with variable boundaries

Troposphere Pollution

• Stationary pollution sources are relatively fixed in location
• Nonpoint sources cannot be easily isolated, while point sources include factories and power plants
• Mobile sources release pollutants while moving from motorized vehicles

Pollutants

• Primary pollutants are emitted directly into the air
• Secondary pollutants are compounds that become harmful by reacting in the atmosphere
• Pollutant sources can be natural

Key Air Pollutants

• Criteria pollutants are the six most regulated pollutants
• Sulfur dioxide, a primary pollutant from burning fossil fuels (coal), affects paper, cement, aluminum production, and causes acid rain
• Nitrogen oxides, primary from human automobiles and fossil fuels, cause smog and acid rain
• Carbon monoxide, mainly from natural sources but also from incomplete combustion in vehicles and heaters, binds strongly to hemoglobin
• Ozone is a secondary pollutant which is harmful in the troposphere but helpful in the stratosphere
• Particulates are solid particles suspended in air from vehicles, farming, fossil fuel burning, windstorms, and volcanic eruptions, they are inhalable and reduce visibility
• Lead comes from automobile batteries and industrial sources, causing chronic bioaccumulation and biomagnification

Combustion

• Ideally combustion is complete but in reality it’s incomplete due to lack of oxygen

Smog, and Air Pollution

• Sulfurous/Industrial smog is from factories burning coal or oil, and contains sulfur oxides and particulates
• Photochemical smog relates to vehicles and is caused by sunlight, chemicals, and thermal inversion concentrating pollutants
• Air pollution concentrates in urban areas and results from natural origins like eruptions and wildfires
• Air pollution is the fourth leading cause of death
• The Philippine Clean Air Act addresses air pollution