Ecosystems and Human Population Ecology Flashcards

Vocabulary flashcards covering ecosystems, atmospheric layers, ecological productivity, thermodynamics, human population dynamics, demographics, and urbanization based on the lecture material.

Atmosphere

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

Troposphere

The innermost atmospheric layer extending $7\text{--}18\,km$ above the equator that contains nearly $80\%$ of total air mass and weather phenomena, with temperature decreasing as altitude increases.

Stratosphere

The atmospheric layer $19\text{--}50\,km$ above the equator containing nitrogen, oxygen, and ozone ($O_3$), where temperature increases with altitude due to exothermic reactions triggered by solar UV rays.

Mesosphere

The atmospheric layer $30\text{--}50\,km$ above the equator with low ozone concentration, where temperature decreases with increasing altitude.

Thermosphere

The atmospheric layer $50\text{--}400\,km$ above the equator where temperatures rise with altitude due to bombardment by solar particles, containing ionized particles that reflect radio waves.

Exosphere

The outermost atmospheric layer starting around $400\,km$ above the equator and extending $10{,}000\,km$ thick, composed of spread-out hydrogen and helium gases separating Earth from space.

Hydrosphere

The aqueous envelope of the Earth including liquid water, water vapor, and ice in surface, atmospheric, and underground forms.

Geosphere

The structural portion of Earth comprising its interior, rocks, minerals, landforms, core, mantle, and crust.

Biosphere

The combined parts of the atmosphere, hydrosphere, and geosphere where living organisms exist.

Ecology

The scientific study of interactions among organisms and between organisms and their nonliving physical environment.

Abiotic Components

The non-living physical and chemical factors, such as light intensity, temperature range, pH, and water availability, that influence organism survival and reproduction.

Biotic Components

All living organisms, their interactions, body parts, and waste products that directly or indirectly influence an ecosystem.

Producers (Autotrophs)

Organisms such as plants and phytoplankton that manufacture organic nutrients from inorganic environment compounds and solar energy using photosynthesis.

Consumers (Heterotrophs)

Organisms that cannot produce their own organic nutrients and must obtain energy by consuming other organisms.

Detritivores

Organisms, such as earthworms and vultures, that consume dead organic matter or waste material (detritus).

Decomposers (Saprotrophs)

Bacteria and fungi that break down dead organic material and return inorganic nutrients back to soil, water, and air.

Habitat

The specific physical location where a given population of a species lives.

Ecological Niche

The functional role or occupation of a species within an ecosystem.

First Law of Thermodynamics

The law stating that energy cannot be created or destroyed, only transformed, maintaining a constant total energy content within a closed system.

Second Law of Thermodynamics

The law stating that the total amount of usable energy in the universe decreases over time as energy is lost in the form of disorganized heat.

Entropy

A quantitative measure of the degree of disorder or unusable energy in a system.

Natural Greenhouse Effect

The mechanism where vibrating gaseous molecules (like $CO_2$ and water vapor) trap heat in the lower atmosphere, keeping the Earth's surface warm.

Photosynthesis

The metabolic pathway represented by $6CO_2 + 12H_2O + \text{radiant energy} \rightarrow C_6H_{12}O_6 + 6H_2O + 6O_2$, converting light energy into stored chemical energy.

Cellular Respiration

The biological process represented by $C_6H_{12}O_6 + 6O_2 + 6H_2O \rightarrow 6CO_2 + 12H_2O + \text{energy}$, releasing stored chemical energy for cellular work.

Trophic Level

A step or feeding level in a food chain consisting of organisms that obtain energy from the same primary source.

Biomass

The total dry weight of all organic matter contained in the organisms at a given trophic level or ecosystem.

Ecological Efficiency

The percentage of usable chemical energy transferred as biomass from one trophic level to the next, typically ranging from $1.3\%$ to $56\%$.

Gross Primary Productivity (GPP)

The total rate at which primary producers convert solar energy into chemical energy in the form of biomass, often expressed in $\text{kcal/m}^2/\text{yr}$.

Net Primary Productivity (NPP)

The net rate of biomass accumulation by producers after subtracting energy lost to aerobic respiration, calculated as $NPP = GPP - R$.

Population Ecology

The study of population dynamics, investigating how and why population size changes over time due to competition, predation, and environmental factors.

Growth Rate ($r$)

The annual percentage change in population size, determined globally by $r = b - d$ and locally by $r = (b - d) + (i - e)$.

Immigration

The movement of individuals entering a population, resulting in a local size increase.

Emigration

The movement of individuals leaving a population, resulting in a local size decrease.

Biotic Potential

The maximum theoretical rate of population growth under ideal environmental conditions.

Exponential Population Growth

Population growth occurring at a constant reproductive rate under ideal conditions, yielding a characteristically $J$-shaped curve.

Environmental Resistance

The collective set of environmental factors, such as resource limits, disease, and predation, that restrict exponential population growth.

Carrying Capacity ($K$)

The maximum population size of a species that a specific environment can sustainably support long-term, yielding an $S$-shaped growth curve.

Population Crash

A severe drop in population density that occurs when a population exceeds its environment's carrying capacity and exhausts critical resources.

Demographics

The applied sociological study of human population statistics, structure, and dynamic changes.

Infant Mortality Rate

The number of infant deaths under age $1$ per $1{,}000$ live births within a population per year.

Replacement-Level Fertility

The average number of children a couple must bear to replace themselves, estimated globally at approximately $2.1$.

Total Fertility Rate (TFR)

The average number of children born alive to a woman during her reproductive years.

Demographic Transition

The multi-stage process through which a nation transitions from high birth and death rates to low birth and death rates as it industrializes.

Age Structure

The relative distribution and proportion of individuals across various age categories in a population.

Population Growth Momentum

The potential for future population growth driven by present age distribution, particularly when a large portion of the population is pre-reproductive.

Microcredit Programs

Financial initiatives offering small loans of \50\text{--}\$500$ to impoverished individuals—mostly women—to establish self-sustaining microenterprises.

Urbanization

The demographic trend involving the migration of populations from rural settings into densely built urban regions.

Brownfields

Abandoned or vacant industrial and commercial sites whose reuse is complicated by real or perceived environmental contamination.

Suburban Sprawl

The expansion of low-density residential and commercial housing outward from central urban cores into undeveloped natural and agricultural areas.

Compact Development

An urban planning concept featuring dense, multi-unit housing situated near mass transit, employment, and commercial services to minimize automobile dependence.

Megacities

Urban agglomerations with total human populations exceeding $10\,\text{million}$ residents.