Environmental Science, Ecosystem Dynamics, and Population Ecology

Comprehensive practice flashcards covering environmental science foundations, ecosystem services, biogeochemical cycles, thermodynamics, population dynamics, and community ecology from lecture chapters 1, 3, and 4.

What is environmental science?

It is the multidisciplinary science of interactions between physical, chemical, and biological components of the environment, including their effects on all types of living organisms.

According to UN estimates for August 2025, what is the global human population size and its annual growth rate?

The global population is $8.24\text{ billion}$ people, with approximately $85\text{ million}$ people added each year.

What trend in global human population growth is illustrated in this historical graph?

The world's human population has increased sixfold in the past $200\text{ years}$, expanding from $1\text{ billion}$ in $1830$ to over $8\text{ billion}$ in $2024$.

What are the three categories of ecosystem goods and services that make up ecosystem capital?

1. Provisioning services (goods like food and fuel)
2. Regulating services (processes like flood protection and water purification)
3. Cultural services (nonmaterial benefits like spiritual values and recreation)

According to Table 1-1 from the Millennium Ecosystem Assessment, what proportion of global ecosystem services have been degraded by human use?

Human use has degraded almost two-thirds ($\approx 67\%$) of identified ecosystem services, while $20\%$ are mixed and $17\%$ have been enhanced.

What is the difference between cumulative impacts and unintended consequences in human environmental interactions?

Cumulative impacts occur when widespread individual actions become major environmental problems over time (e.g., tree cutting, fishing), whereas unintended consequences arise when lack of attention to processes leads to unexpected negative outcomes (e.g., pesticide pollution, waste disposal).

Which 1962 book by Rachel Carson highlighted the environmental dangers of pesticides such as DDT?

Silent Spring

Which major U.S. environmental laws protecting air, water, wildlife, and land are highlighted in this modern environmental movement timeline?

NPS Organic Act ($1916$), Wilderness Act ($1964$), Wild and Scenic Rivers Act ($1968$), National Environmental Policy Act ($1969$), Clean Water Act ($1972$), Coastal Zone Management Act ($1972$), Endangered Species Act ($1973$), and Safe Drinking Water Act ($1974$).

What are the three essential themes required for maintaining a productive relationship with the natural world?

1. Sustainability (continuing processes without depleting energy or material resources)
2. Sound science (scientific work based on peer-reviewed research)
3. Stewardship (managing natural resources and human well-being for the common good)

How do a scientific hypothesis and a scientific theory differ?

A hypothesis is an educated guess regarding an observation that is tested through experimentation, whereas a theory is a hypothesis that has been rigorously tested, confirmed, and provides a logically consistent framework for all relevant facts.

What does the Law of Conservation of Matter state?

Atoms do not change and are neither created nor destroyed during chemical reactions.

What are the four main interconnected spheres of Earth?

1. Atmosphere (thin gas layer)
2. Hydrosphere (all water in oceans, rivers, ice, and groundwater)
3. Lithosphere (rigid outer crust and upper mantle)
4. Biosphere (the sum of all living systems)

What phase transitions of water are depicted across solid, liquid, and gas states in this diagram?

Solid to gas (sublimation), gas to solid (deposition), gas to liquid (condensation), liquid to gas (vaporization/evaporation), liquid to solid (freezing), and solid to liquid (melting).

How do organic compounds differ structurally from inorganic compounds?

Organic compounds possess $C-H$ bonds in their chemical structures, whereas inorganic compounds contain neither carbon-carbon nor carbon-hydrogen bonds.

How is a calorie defined in terms of energy measurement?

The amount of heat required to raise the temperature of $1\text{ gram}$ of water by $1^\circ\text{C}$.

What do the First and Second Laws of Thermodynamics state regarding energy and entropy?

The First Law states that energy is neither created nor destroyed but can be converted between forms. The Second Law states that in any energy conversion, usable energy is lost and total entropy (disorder) increases.

What is the balanced chemical equation for photosynthesis?

$$6\,CO_2 + 6\,H_2O + \text{light E} \rightarrow C_6H_{12}O_6 + 6\,O_2$$

What is the balanced chemical equation and energy efficiency of cellular respiration?

$C_6H_{12}O_6 + 6\,O_2 \rightarrow 6\,CO_2 + 6\,H_2O + \text{energy}$, operating at an efficiency of $40\text{--}60\%$.

How does energy movement in an ecosystem differ from nutrient movement?

Energy flows in a one-way direction through an ecosystem and is lost as heat (requiring continuous replenishment from sunlight), whereas nutrients are recycled continuously through biogeochemical cycles.

Which major nutrient cycle, pictured in this summary diagram, is completely unattached to the atmosphere?

The phosphorus cycle, which relies on the weathering of inorganic phosphate ($PO_4^{3-}$) rocks in the lithosphere.

What is nitrogen fixation, and what forms of reactive nitrogen ($N_r$) does it produce?

Nitrogen fixation converts nonreactive atmospheric nitrogen gas ($N_2$) into usable reactive nitrogen forms, primarily ammonium ($NH_4^+$) and nitrate ($NO_3^-$).

What occurs during the microbial process of denitrification?

Microbes in oxygen-poor soils and sediments use nitrate ($NO_3^-$) in anaerobic cellular respiration, converting it back into atmospheric nitrogen gas ($N_2$).

According to this global sulfur cycle diagram, through what pathways does sulfur enter the air, land, or water?

Weathering of rocks, volcanic activity, fossil fuel combustion (coal/petroleum), mining of metals, sea spray, and wetland emissions.

What is an ecotone?

A transitional region between two distinct ecosystems that shares species and physical characteristics of both.

What temperature growth zones are illustrated along this species tolerance curve?

Optimal range (highest rate of growth), zones of stress (increasing stress), range of tolerance (entire span allowing growth), and limits of tolerance (thresholds beyond which death occurs).

What is the Law of Limiting Factors?

Any environmental factor outside an organism's optimal range (whether too much or too little) will cause stress and limit growth, survival, and reproduction.

How do habitat and niche differ?

A habitat is the physical place where a species lives (defined by vegetation and environment), whereas a niche includes all biotic and abiotic factors and roles with which the organism interacts.

What equation defines change in population size over time?

$$\text{Change in population number} = (\text{Births} + \text{Immigration}) - (\text{Deaths} + \text{Emigration})$$

What is carrying capacity ($K$)?

The maximum population size of a species that a given habitat can support indefinitely without being degraded or ruined.

What opposing factors balance population density in an ecosystem as shown in this gauge model?

Biotic potential (reproductive rate, migration/dispersion ability, invasion ability, defense mechanisms) and Environmental resistance (lack of food/water/habitat, adverse weather, predators, disease, parasites, competitors).

How do $r$-strategists and $K$-strategists differ along the reproductive strategy spectrum shown here?

$r$-strategists produce vast numbers of offspring with low recruitment and short lifespans (e.g., oysters, tuna), whereas $K$-strategists produce few offspring, invest heavily in parental care, and maintain stable populations near carrying capacity (e.g., pumas, chimpanzees).

What is a critical number in population dynamics?

The minimum population size allowing survival and recovery of a species; falling below this number makes extinction almost inevitable.

What is the difference between density-dependent and density-independent factors?

Density-dependent factors intensify their impact as population density increases (e.g., disease, predation, food shortages), whereas density-independent factors exert mortality regardless of density (e.g., fire, flooding, pollution).

How does resource partitioning reduce competition among warbler species foraging on the same tree?

By dividing and specializing the resource across different foraging heights on the tree, species minimize direct competition and dedicate more energy to reproduction.

What is a keystone species, and what happened when sea otters were removed from Pacific marine ecosystems?

A keystone species plays a crucial role in maintaining biotic ecosystem structure; removing sea otters allowed sea urchins to overgraze kelp forests, destroying the habitat for numerous other species.

What traits separate highly vulnerable species from highly adaptive species facing rapid abiotic environmental changes?

Vulnerable species have narrow distributions, small populations, low biotic potential, and long generation times (leading to extinction), whereas adaptive species have wide distributions, large populations, high genetic variation, high biotic potential, and short generation times (leading to survival/speciation).

How do plate tectonics contribute to the formation of new species?

The slow movement of Earth's $14$ major tectonic plates geographically isolates separated populations, exposing them to different selective pressures that drive speciation over long periods.