Mastering Biology Chapter 29- Energy flow and Nutrient Cycling in Ecosystems

Clean Air Act Amendments of 1990

-Amendments to the Clean Air Act in 1990 led to reductions in sulfur dioxide and nitrogen oxide emissions from power plants -reduced sulfur emissions have improved air quality and rain acidity in some regions -atmospheric nitrogen compounds have shown a small overall increase, due to increased gasoline burning by automobiles

Food chains

-a linear feeding relationship with just one representative at each trophic level -plants are the dominant producers in terrestrial ecosystems -photosynthetic protists and bacteria (phytoplankton) are the dominant producers in aquatic ecosystems

Energy transfer

-a small percentage of available energy transfers to the next trophic level -energy pyramids illustrate energy transfer between trophic levels -the average net energy transfer between trophic levels is roughly 10% efficient -the dominant organisms in a community are usually autotrophs (producers)

Acid rain

-due to excess industrial production of sulfur dioxide and nitrogen oxides that are overloaded in the atmosphere -sulfur dioxide: released primarily from coal and oil power plants -nitrogen oxides: released mainly from vehicles, power plants, and industries -damages trees and crops -alters lake communities -increases exposure of organisms to toxic metals because they are far more soluble in acidified water

Energy and nutrient pathways

-ecosystems have biotic and abiotic components -energy moves in a one-way flow through communities within ecosystems -nutrients, from which molecules of life are built, constantly cycle within and among ecosystems

The trophic level

-electromagnetic waves carry energy from the sun to the Earth -photosynthetic organisms capture sunlight's energy and convert it to chemical energy -energy flows through a series of trophic levels... 1) producers (autotrophs): make their own food using inorganic nutrients and energy from the environment 2) primary consumers (heterotrophs): feed directly and exclusively on producers 3) the higher-level consumers: feed on herbivores or other carnivores 4) tertiary consumers

Net primary productivity

-energy that producers store over a given period -determines how much life an ecosystem can support -can be measured as the amount of energy (calories) or biomass (total dry weight of biological material) stored per unit area over time -influenced by many factors... -the availability of nutrients and sunlight to producers -the availability of water -the temperature

Harmful algal bloom

-fertilizers containing nitrogen and phosphate that runoff from agricultural lands and large livestock operations may cause excessive algal growth -reduces species diversity (creating dead zones) and harms water quality -not all species of algae do this

Severe consequences

-glaciers and ice sheets have been melting at unprecedented rates -more extreme weather patterns are predicted -warming air and water currents are changing the precipitation patterns on land -forests may suffer loss of species -coral reefs may decline due to warming waters -studies have documented shifts in species' ranges towards the poles -it may have direct impacts on human health

Interfering with the carbon cycle

-greenhouse gasses trap sunlight energy in a planet's atmosphere as heat -CO2 participates in the greenhouse effect -interfering with the cycle may change Earth's climate -since 1850, atmospheric CO2 has increased by 40% -global temperature has increased in parallel with rising atmospheric CO2 levels

Nitrogen cycle

-major reservoir is N2 in the atmosphere -nitrogen fixing bacteria in water and soil or in roots of legumes convert N2 to NH3 (ammonia) through nitrogen fixation -some bacteria in soil and water convert NH3 to NO3 (nitrate) -producers incorporate nitrogen from NO3 or NH3 into biological molecules -decomposer bacteria convert nitrogen in wastes and dead bodies back to NH3 and NO3 in the soil or water -denitrifying bacteria break down NO3, releasing N2 back into the atmosphere

Phosphorus cycle

-major reservoir is PO4 (phosphate) in rocks -PO4 in rocks can be dissolved in water -PO4 is absorbed by autotrophs, where it is incorporated into biological molecules that pass through food webs -at each level, excess phosphorus is excreted -decomposers release PO4 -PO4 may be reabsorbed by autotrophs or reincorporated into rock -almost all phosphorus remains as PO4 throughout its cycle -affected by all living organisms

Hydrologic cycle

-major reservoir of water is the ocean -underground reservoirs of water are aquifers -solar energy evaporates water, and it comes back to Earth as precipitation -water that falls on land takes various paths -continually restores the fresh water needed for terrestrial communities -water molecules remain chemically unchanged throughout the cycle -not affected by living organisms

Carbon cycle

-major short-term reservoirs is CO2 in the atmosphere and the oceans -long term reservoirs are fossil fuels and limestone -carbon enters communities through fixing carbon from CO2 into biological molecules during photosynthesis -cellular respiration by organisms releases CO2 into the atmosphere and oceans -affected by all living organisms

Food webs

-shows the actual feeding relationships in a community, including its many interconnecting food chains -omnivores are primary, secondary, and tertiary consumers -detritivores and decomposers release nutrients for reuse

Nutrient cycle

-the pathways nutrients follow between communities and reservoirs -nutrients: elements and small molecules that form all the chemical building blocks of life -macronutrients: required by organisms in large quantities (water) -micronutrients: required by organisms only in trace quantities (iron, molybdenum, selenium)

In the food web shown, the arrows point to where the __________ flow(s)

Energy

Which trophic level(s) must be present to sustain any ecosystem?

Producers, detritivores, and decomposers

Which of the following is unlikely to occur due to global warming?

The amount of disease-carrying organisms will decrease

Which statement about the effects of burning fossil fuels is correct?

The burning of fossil fuels increases carbon dioxide levels, and the destruction of the rain forests kills off the plants that take carbon dioxide out of the atmosphere

There is more biomass found in the tropical rain forest than in the tundra. This indicates that _____________

The rain forest has a greater amount of primary productivity than the tundra

Acidic water soaks up toxic metals such as lead, mercury, and aluminum. Why will this have a greater effect on the higher trophic levels?

Toxic substances accumulate with increasing concentrations at higher trophic levels, a phenomenon called biological magnification

Net primary production per unit area is likely to be highest in which of the following ecosystems?

Tropical rain forests