Human Population Ecology and Ecosystems Review

Comprehensive vocabulary flashcards covering population ecology, growth rate formulas, demographic transition stages, atmospheric layers, ecological levels, and thermodynamics principles from the lecture notes.

Population Ecology

The study of how and why a population increases or decreases over time due to environmental pressures like competition, disease, and predation.

Growth Rate ($r$)

The rate of population change calculated by subtracting death rate ($d$) from birth rate ($b$): $r = b - d$. When accounting for dispersal, it is $r = (b - d) + (i - e)$, where $i$ is immigration and $e$ is emigration.

Biotic Potential

The maximum rate of population increase under ideal conditions, resulting in exponential growth and a J-shaped curve.

Environmental Resistance

Limits placed on exponential growth (such as declining food, water, and shelter), which cause the population to level out at the carrying capacity ($K$).

Carrying Capacity ($K$)

The limit at which population growth stabilizes, producing an S-shaped curve (logistic growth). Earth's carrying capacity for humans is estimated between $4\text{ billion}$ and $16\text{ billion}$.

Logistic Growth

Population growth that stabilizes at the environment's carrying capacity ($K$), producing an S-shaped curve.

Population Crash

A sudden drop in population density caused by exhausted resources.

Replacement-Level Fertility

The number of children a couple must produce to replace themselves, estimated at $2.1$.

Total Fertility Rate (TFR)

The average number of children born to each woman.

Preindustrial Stage

Stage 1 of the demographic transition where women have many children, but high infant mortality leads to very slow population growth.

Transitional Stage

Stage 2 of the demographic transition characterized by lowered death rates due to improved health care and food supplies while birth rates remain high, resulting in rapid population growth.

Industrial Stage

Stage 3 of the demographic transition where a decline in the birth rate slows population growth despite relatively low death rates.

Postindustrial Stage

Stage 4 of the demographic transition where better education and affluence lead people to limit family size, causing population to grow very slowly or not at all.

Age Structure Diagrams

Diagrams that illustrate the proportion of a population across pre-reproductive ($0\text{--}14\text{ years}$), reproductive ($15\text{--}44\text{ years}$), and post-reproductive ($45+\text{ years}$) age groups.

Positive Population Growth Momentum

Momentum that occurs when a large percentage of the population is pre-reproductive, leading to continued growth even if fertility declines.

Negative Population Growth Momentum

Momentum that occurs when a smaller proportion of the population is pre-reproductive, leading to smaller subsequent generations.

Urbanization

The movement of people from rural areas to densely populated cities in search of better economic and educational opportunities.

Brownfields

Abandoned, vacant factories or residential sites that are contaminated from past uses and require cleaning before redevelopment.

Suburban Sprawl

The expansion of development around a city that encroaches on natural areas and increases heavy reliance on motor vehicles.

Eco-Cities

Cities that utilize compact development to build multiple-unit residential buildings close to jobs and public transit, maximizing land use efficiency and reducing pollution.

Atmosphere

A thin spherical envelope of gases surrounding the surface of the Earth.

Hydrosphere

The aqueous envelope containing Earth's liquid water, water vapor, and ice.

Geosphere

The Earth's interior, rocks, minerals, and landforms comprising the core, mantle, and crust.

Biosphere

The parts of the atmosphere, hydrosphere, and geosphere where life is found.

Troposphere

The thinnest atmospheric layer closest to Earth's surface ($7\text{--}18\,km$), holding $80\%$ of air mass and water vapor, where active weather occurs and temperature decreases with altitude.

Stratosphere

The atmospheric layer ($19\text{--}50\,km$) containing nitrogen, oxygen, and the ozone layer, where temperature increases with altitude due to exothermic reactions from UV radiation.

Mesosphere

The atmospheric layer ($30\text{--}50\,km$) characterized by low gas concentrations and decreasing temperatures with altitude.

Thermosphere (Ionosphere)

The atmospheric layer ($50\text{--}400\,km$) that reflects radio waves and produces auroras; temperature increases with altitude due to energetic solar particles bombarding gas molecules.

Exosphere

The outermost atmospheric layer ($\sim 400\,km$ and above) consisting of spread-out hydrogen and helium in very cold, empty space.

Ecology

The study of interactions of living things with each other and their physical environment across five levels: organism, population, community, ecosystem, and biosphere.

Habitat

The specific place where a population lives.

Ecological Niche

The functional role a species fulfills within an ecosystem.

Abiotic Components

Non-living physical and chemical factors in an ecosystem, including light intensity, temperature, moisture, minerals, and pH.

Limiting Factors

Abiotic variables that dictate which organisms can survive in a particular environment.

Biotic Components

All living things in an ecosystem, including their parts, interactions, and wastes.

Producers (Autotrophs)

Organisms such as plants and phytoplankton that produce their own nutrients via photosynthesis.

Consumers (Heterotrophs)

Organisms that cannot produce their own nutrients, encompassing herbivores, carnivores, and omnivores.

Detritivores

Organisms that feed on the dead bodies and wastes of other organisms.

Decomposers (Saprotrophs)

Organisms that cause decay and return nutrients back to the environment.

First Law of Thermodynamics

The law stating that energy cannot be created or destroyed, only transformed from one form to another.

Second Law of Thermodynamics

The law stating that usable energy decreases over time as some is lost as heat, increasing entropy.

Photosynthesis Equation

The chemical process expressed as $6CO_2 + 12H_2O + \text{radiant energy} \rightarrow C_6H_{12}O_6 + 6H_2O + 6O_2$.

Cellular Respiration Equation

The chemical process expressed as $C_6H_{12}O_6 + 6O_2 + 6H_2O \rightarrow 6CO_2 + 12H_2O + \text{energy}$.

Food Chain

A linear path of energy transfer through an ecosystem's trophic levels.

Food Web

A complex network of interconnected food chains within an ecosystem.

Ecological Efficiency

The percentage of usable energy transferred between trophic levels, ranging from $1.3\%$ to $56\%$, with $44\%$ to $98.7\%$ of energy lost at each step.

Gross Primary Productivity (GPP)

The rate at which producers convert solar energy into chemical energy stored in biomass.

Net Primary Productivity (NPP)

Gross Primary Productivity (GPP) minus the rate at which producers use stored energy through respiration, which limits the number of consumers an ecosystem can support.