AP Environmental Science Unit 1 - Living World: Ecosystems Study Guide

50 practice question-and-answer flashcards covering Unit 1: Living World - Ecosystems, including biomes, biogeochemical cycles, primary productivity, and energy flow.

What is the difference between predator-prey relationships and herbivory?

In predator-prey interactions, a predator hunts, kills, and consumes another animal (prey). In herbivory, an organism feeds on primary producers (plants or algae), typically eating plant parts without killing the entire plant.

What is symbiosis, and what are the three main types?

Symbiosis is a close, long-term biological interaction between two different species. The three types are mutualism (both benefit: $+/+$), commensalism (one benefits, one unaffected: $+/0$), and parasitism (one benefits at the expense of the other: $+/-$).

How does competition differ within a species compared to between two different species?

Intraspecific competition occurs between members of the same species for identical resources, while interspecific competition occurs between members of two different species when their ecological niches overlap for limited resources.

What limited resources do animals compete for, and what do plants compete for?

Animals compete for food, water, territory, shelter, and mates. Plants compete for sunlight, soil moisture/water, physical space, and soil nutrients such as nitrogen and phosphorus.

Why do organisms avoid competition, and what is the role of resource partitioning (niche partitioning)?

Direct competition requires energy expenditure and can lead to injury, lower reproductive success, or competitive exclusion. Resource partitioning allows species to divide limited resources so they can reduce competition and coexist.

What are the three types of resource partitioning, and what is an example of each?

Spatial partitioning occurs when species occupy different physical locations (e.g., birds foraging at different tree heights); temporal partitioning occurs when species use resources at different times (e.g., bats hunting at night, hawks hunting by day); dietary partitioning occurs when species consume different food types or sizes (e.g., finches with different beak sizes eating different seeds).

What is a biome?

A biome is a large, naturally occurring regional community of plants and animals occupying a major habitat defined by characteristic climate, soil conditions, and vegetation types.

What are nine major terrestrial biomes moving generally from the equator toward the North Pole?

Tropical rainforest, tropical seasonal forest/savanna, subtropical desert, woodland/shrubland (chaparral), temperate grassland, temperate deciduous forest, temperate rainforest, boreal forest (taiga), and tundra.

What are the two primary factors that determine the climate and type of a terrestrial biome?

Average temperature and average precipitation.

How does the angle of insolation change with latitude, and how does that affect temperature and precipitation?

Insolation is most direct and concentrated at the equator ($0^\circ$), producing warm temperatures and high evaporation that causes heavy rainfall. At higher latitudes, solar radiation strikes obliquely across a larger surface area, causing lower temperatures and reduced evaporation.

How do mountains create a rain shadow effect?

Moist air blows inland and is forced up the windward side of a mountain, where it expands, cools, condenses, and releases precipitation. The dry air then descends on the leeward side, warming and absorbing moisture to create an arid region called a rain shadow.

How do temperature, precipitation, and biomes change with elevation?

As elevation increases, atmospheric pressure drops, causing temperatures to decrease and precipitation patterns to shift; this creates distinct altitudinal bands of biomes that mirror the progression of biomes seen when traveling toward higher latitudes.

How does proximity to large bodies of water affect regional temperature, and what property of water explains this?

Large bodies of water have a high specific heat capacity, meaning they absorb and release heat slowly. This moderates coastal climates, preventing extreme temperature fluctuations and producing cooler summers and milder winters compared to inland areas.

How do ocean currents, such as the Gulf Stream, affect the climate of coastal regions like the United Kingdom?

The Gulf Stream carries warm tropical water northward across the Atlantic, warming the overlying air mass and bringing milder winter temperatures and higher humidity to the United Kingdom than other regions at the same latitude.

What is ocean upwelling, and what four impacts does it have on coastlines like California?

Upwelling is the wind-driven process where surface water is pushed away from shore and replaced by cold, nutrient-rich deep ocean water. Its four impacts include: cold sea-surface temperatures, frequent coastal fog, high concentrations of marine nutrients, and highly productive fisheries.

How does unequal heating of the Earth create wind, and what conditions are associated with high versus low pressure?

Unequal heating causes warm air to expand, become less dense, and rise, forming low-pressure zones; cooler, denser air sinks, forming high-pressure zones. Air flows horizontally from high to low pressure as wind. Low pressure brings rising air, clouds, and rainy conditions; high pressure brings sinking air and sunny, dry conditions.

What is a Hadley cell, and at what latitudes do we expect high precipitation versus arid deserts?

A Hadley cell is a global tropical atmospheric circulation pattern where solar heating causes air to rise at the equator ($0^\circ$), generating heavy rain; the dry air moves poleward and sinks at approximately $30^\circ\text{ N}$ and $30^\circ\text{ S}$, producing high pressure and arid deserts.

Which nutrients are most commonly limited in marine ecosystems versus terrestrial land ecosystems?

In ocean ecosystems, nitrogen, phosphorus, and iron are commonly limiting; in terrestrial land ecosystems, nitrogen and phosphorus are the primary limiting nutrients for plant growth.

Which terrestrial biome has the least organic soil nutrients, and which has the most?

Tropical rainforests have the least organic nutrients in their soil due to rapid decomposition and rapid plant uptake; temperate grasslands and temperate deciduous forests have the most organic soil nutrients due to seasonal leaf litter accumulation and deep, dense root systems.

Why do deciduous trees lose their leaves, and what adaptations allow evergreen trees to retain needles year-round?

Deciduous trees shed leaves to avoid water loss through transpiration and tissue damage during cold, dry winters. Evergreen conifers have narrow needle-like leaves with small surface area and thick, waxy cuticles that minimize water loss and survive freezing temperatures.

Why are desert plants often light or silver in color, while understory forest plants are often dark green?

Desert plants have light or silver leaves with reflective hairs to reflect intense solar radiation and reduce heat absorption and water loss. Forest understory plants are dark green because they produce dense concentrations of chlorophyll pigments to maximize absorption of low-intensity light filtering through the canopy.

What five environmental factors influence how many trees a terrestrial biome can grow by affecting the rate of photosynthesis?

1. Sunlight availability/intensity, 2. Water/precipitation availability, 3. Ambient temperature, 4. Soil nutrient availability (such as nitrogen and phosphorus), and 5. Carbon dioxide ($\text{CO}_2$) concentration.

How will current global climate change shift the geographic distribution of terrestrial biomes?

Biomes will shift poleward in latitude and upward in elevation as global temperatures rise; warmer and drier biomes like deserts and scrublands will expand, while cold biomes like the arctic tundra and alpine zones will shrink.

What are the primary freshwater biomes, and why is high-quality fresh water vital to humans?

Freshwater biomes include streams, rivers, ponds, lakes, and freshwater wetlands. High-quality fresh water is vital for human survival, drinking water, agricultural irrigation, sanitation, and industrial processes.

What are the primary marine biomes, and which atmospheric gases are absorbed and produced by marine algae?

Marine biomes include oceans, coral reefs, kelp forests, estuaries, and salt marshes. Marine algae absorb carbon dioxide ($\text{CO}_2$) from the atmosphere during photosynthesis and produce oxygen gas ($\text{O}_2$).

What five abiotic factors regulate the global primary production of marine algae?

1. Sunlight intensity and penetration depth, 2. Water temperature, 3. Nutrient concentrations (nitrates and phosphates), 4. Salinity levels, and 5. Dissolved carbon dioxide ($\text{CO}_2$) and dissolved oxygen levels.

What is a biogeochemical cycle, and what is the difference between a source and a sink?

A biogeochemical cycle is the pathway by which a chemical element or molecule moves through the biological, geological, and chemical systems of Earth. A source releases more of the element into circulation than it takes in, while a sink absorbs and stores more than it releases.

What are examples of slow carbon cycle sinks versus fast carbon cycle sinks?

Slow carbon sinks store carbon for thousands to millions of years, such as sedimentary rocks (limestone), fossil fuels underground, and deep ocean sediments. Fast carbon sinks cycle carbon over short time scales, such as living plants/animals, the atmosphere, and shallow surface ocean waters.

What chemical reactions do plants and animals perform to cycle carbon?

Plants fix carbon through photosynthesis: $6\text{CO}_2 + 6\text{H}_2\text{O} + \text{light} \rightarrow \text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2$. Plants and animals release carbon through cellular respiration: $\text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2 \rightarrow 6\text{CO}_2 + 6\text{H}_2\text{O} + \text{ATP}$.

Where does stored underground carbon end up when humans extract and burn fossil fuels?

The carbon stored in fossil fuels is combusted and rapidly released into the atmosphere as carbon dioxide ($\text{CO}_2$), increasing greenhouse gas concentrations.

What are three major nitrogen sinks, which is the largest, and are they held for a short or long period?

The three sinks are the atmosphere (the largest reservoir, held long-term as $N_2$ gas), soils/sediments (held short-to-medium term), and living organic biomass (held short-term).

What are the four main bacterial processes in the nitrogen cycle and the chemical forms before and after each reaction?

1. Nitrogen Fixation: $N_2 \rightarrow NH_3$ or $NH_4^+$; 2. Nitrification: $NH_3/NH_4^+ \rightarrow NO_2^- \rightarrow NO_3^-$; 3. Assimilation/Ammonification: Organic nitrogen $\rightarrow NH_3/NH_4^+$; 4. Denitrification: $NO_3^- \rightarrow N_2O \rightarrow N_2$.

How does bacterial nitrogen fixation affect plants and soil, and which forms of nitrogen can plants assimilate?

Nitrogen-fixing bacteria convert unreactive atmospheric $N_2$ into plant-usable nitrogen compounds that enrich soil fertility; plants directly assimilate nitrogen primarily as nitrate ($NO_3^-$) and ammonium ($NH_4^+$).

How do humans alter the nitrogen cycle given that nitrogen is a limiting plant nutrient?

Humans artificially fix atmospheric nitrogen using industrial processes (the Haber-Bosch process) to manufacture chemical fertilizers; applying excess fertilizers leads to agricultural runoff, aquatic eutrophication, and nitrous oxide emissions.

What is the primary reservoir for phosphorus, and what major environmental sink is absent in the phosphorus cycle?

The main reservoir for phosphorus is sedimentary rock and geological deposits; an atmospheric gas phase is completely absent from the phosphorus cycle.

Why is phosphorus typically limited in terrestrial soils and oceans?

Because phosphorus lacks an atmospheric gas phase, it enters ecosystems only via the very slow geological weathering of rocks, making its natural release and replenishment in soils and water bodies extremely slow.

How do human activities impact the phosphorus cycle?

Humans mine geological phosphate rock to produce commercial fertilizers and laundry detergents; agricultural and wastewater runoff dumps excess phosphates into aquatic ecosystems, causing eutrophication and oxygen-depleted dead zones.

What fundamental energy source drives the hydrologic (water) cycle?

Solar energy (insolation from the Sun), along with the downward pull of gravity.

What processes describe the phase changes of water: liquid to gas, gas to liquid, liquid to solid, and solid to liquid?

Liquid to gas: evaporation (and plant transpiration); Gas to liquid: condensation; Liquid to solid: freezing; Solid to liquid: melting.

What percentage of Earth's total water is in oceans, ice caps, groundwater, rivers/lakes, and the atmosphere, and what total percent is freshwater?

Oceans hold approximately $97\%$, ice caps and glaciers hold $\approx 2\%$, groundwater holds $\approx 0.7\%$, lakes and rivers hold $\approx 0.01\%$, and the atmosphere holds $\approx 0.001\%$. Total freshwater constitutes only $\approx 2.5\text{--}3\%$ of all water on Earth.

What is primary productivity, and what biochemical reaction generates all plant tissue production?

Primary productivity is the rate at which photosynthetic organisms (producers) synthesize new organic matter from solar energy. The chemical reaction that drives this production is photosynthesis.

What environmental factors determine the primary productivity of terrestrial biomes versus aquatic biomes?

On land, primary productivity is controlled by solar insolation, temperature, water/rainfall, and soil nutrients. In water, it is controlled by light penetration, water temperature, dissolved nutrient levels (nitrogen/phosphorus), and dissolved carbon dioxide.

What are Gross Primary Productivity (GPP) and Net Primary Productivity (NPP), and what equation links them?

GPP is the total rate of solar energy converted into chemical biomass by autotrophs. NPP is the remaining energy stored after plants consume energy for their own cellular respiration ($R$). The formula is: $NPP = GPP - R$.

What are the standard units used to express primary productivity in mass version versus energy version?

Mass version: $\text{g/m}^2/\text{yr}$ (or $\text{g C/m}^2/\text{yr}$). Energy version: $\text{kcal/m}^2/\text{yr}$ (or $\text{kJ/m}^2/\text{yr}$).

Down to what depth does primary productivity occur in aquatic ecosystems, what is this zone called, and how have algae adapted to light penetration?

Primary productivity occurs down to approximately $200\,\text{m}$ in the photic (euphotic) zone; because red light penetrates only the top $1\,\text{m}$, marine algae have adapted accessory pigments to use deeper-penetrating blue-green light.

Based on the graph, which aquatic and which terrestrial biome have the highest average net primary productivity (NPP), and which has the highest percentage of Earth's total net primary production?

Algal beds and reefs have the highest average NPP among aquatic biomes ($\approx 2500\,\text{g/m}^2/\text{yr}$), and tropical wet forests have the highest average NPP among terrestrial biomes ($\approx 2200\,\text{g/m}^2/\text{yr}$). Tropical wet forests produce the highest percentage of Earth's NPP among terrestrial biomes ($\approx 22\%$), while the open ocean produces the highest percentage of Earth's total NPP ($\approx 24\%$) because it covers over $65\%$ of Earth's surface area despite low average productivity.

What are ecological trophic levels by number and consumer/producer type, and what supplies the base energy?

Level 1: Primary Producers (autotrophs); Level 2: Primary Consumers (herbivores); Level 3: Secondary Consumers (carnivores/omnivores); Level 4: Tertiary Consumers (top predators). The Sun supplies the initial energy for terrestrial and near-surface aquatic ecosystems, and energy is transferred along food chains when organisms feed on lower levels.

What is the ecological role of decomposers, and what are two examples each of decomposers, detritivores, and scavengers?

Decomposers break down dead biomass and waste, recycling essential inorganic nutrients back to soil and water. Decomposers: fungi and bacteria. Detritivores: earthworms and millipedes. Scavengers: vultures and hyenas.

What is the 10% Rule of energy flow, what happens to the other 90%, and which law of thermodynamics applies?

The 10% Rule states that only about $10\%$ of the usable energy at one trophic level is transferred to the next level. The other $90\%$ is lost as metabolic heat or used by organisms for cellular work, illustrating the Second Law of Thermodynamics.

A prairie grass ecosystem captures approximately $50{,}000\,\text{calories}$ available to consumers. Based on the 10% Rule, how many calories will be available to secondary consumers?

Primary consumers receive $10\%$ of producer energy ($50{,}000 \times 0.10 = 5{,}000\,\text{calories}$), and secondary consumers receive $10\%$ of primary consumer energy ($5{,}000 \times 0.10 = 500\,\text{calories}$). The correct answer is B (500 calories).

An estuary has an NPP of $8800\,\text{kcal/m}^2/\text{year}$. If $1\,\text{gram} = 4\,\text{kcal}$, convert this NPP into $\text{grams/m}^2/\text{year}$.

$\frac{8800\,\text{kcal/m}^2/\text{year}}{4\,\text{kcal/gram}} = 2200\,\text{grams/m}^2/\text{year}$.

Based on the provided graph, if the average NPP of an estuary is $8800\,\text{kcal/m}^2/\text{yr}$ and its respiration is $79{,}200\,\text{kcal/m}^2/\text{yr}$, what is the gross primary productivity (GPP) of the ecosystem in $\text{kcal/m}^2/\text{yr}$?

Using $NPP = GPP - R$, solve for GPP: $GPP = NPP + R$. Therefore, $GPP = 8800\,\text{kcal/m}^2/\text{yr} + 79{,}200\,\text{kcal/m}^2/\text{yr} = 88{,}000\,\text{kcal/m}^2/\text{yr}$.