Ecosystems and Global Ecology
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62 Terms
What is an ecosystem?
A community of organisms and their physical environment connected by energy flow and nutrient cycling.
What are primary producers?
Autotrophs that convert sunlight into chemical energy.
What are consumers?
Organisms that obtain energy by eating other organisms.
What do decomposers do?
Break down dead organisms and recycle nutrients.
What do detritivores eat?
Dead organic matter
What is a herbivore?
An animal that eats plants.
What is a carnivore?
An animal that eats other animals.
What is an omnivore?
An animal that eats both plants and animals.
What is a parasite?
An organism that lives on or in another organism and benefits at its expense.
Where does most energy in an ecosystem come from?
The Sun.
What is a food chain?
A sequence showing how energy moves from one organism to another.
What is a food web?
Multiple interconnected food chains.
What is a trophic level?
An organism's feeding level in a food chain.
What is the first trophic level?
Producers.
Why are food chains usually short?
Energy is lost at each trophic level.
What is the 10% rule?
Only about 10% of energy passes to the next trophic level.
What happens to the other 90% of energy?
It is used for metabolism and lost as heat.
What is primary productivity?
The conversion of sunlight into chemical energy by producers.
What is gross primary productivity
Total energy captured by photosynthesis.
What is net primary productivity (NPP)?
GPP minus energy used for respiration.
What is biomass?
The total amount of living material in an ecosystem.
Why do ecological pyramids have broad bases and narrow tops?
Because energy decreases at each trophic level.
Why are large animals usually herbivores?
More energy is available lower on the food chain.
Why is eating lower on the food chain more energy efficient?
Less energy is lost between trophic levels.
What is biological magnification?
The increase in concentration of toxins at higher trophic levels.
What chemical is a classic example of biological magnification?
DDT.
What is a biogeochemical cycle?
The movement of nutrients between organisms and the environment.
What are the four major biogeochemical cycles?
Water, Carbon, Nitrogen, and Phosphorus.
What is the largest reservoir of Earth's water?
The oceans.
In what form is most atmospheric carbon found?
Carbon dioxide (CO₂).
What adds CO₂ to the atmosphere?
Respiration, volcanoes, and burning fossil fuels.
What removes CO₂ from the atmosphere?
Photosynthesis.
What is the greenhouse effect?
Greenhouse gases trap heat in Earth's atmosphere.
Why are rising CO₂ levels a concern?
They contribute to global warming.
Why can't most organisms use atmospheric nitrogen directly?
It must first be converted by nitrogen-fixing bacteria.
What do nitrogen-fixing bacteria produce?
Ammonia, ammonium, nitrites, and nitrates.
Where are many nitrogen-fixing bacteria found?
n root nodules of plants.
Why is phosphorus important?
It is needed for ATP, DNA, RNA, and phospholipids.
Why is phosphorus often added to fertilizers?
It is commonly a limiting nutrient.
What is eutrophication?
Excess nutrients cause algal blooms that reduce oxygen in water.
What is the biosphere?
All places on Earth where life exists.
What is a biome?
A large region defined by climate, vegetation, and animal life.
What factors determine climate?
Solar radiation, seasons, air flow, precipitation, and ocean currents.
What causes seasons?
Earth's tilt.
What is the Coriolis Effect?
Earth's rotation causes moving air and water to curve.
What causes rain shadows?
Mountains block moist air, creating dry conditions on the opposite side.
What is the tundra?
A cold biome with permafrost and short plants.
What is another name for the boreal forest?
Taiga.
What trees dominate the boreal forest?
Conifers.
What characterizes temperate deciduous forests?
Trees lose their leaves each winter.
What climate supports grasslands?
Moderate rainfall with warm summers and cold winters.
What characterizes chaparral?
Mild wet winters, hot dry summers, and fire-adapted shrubs.
What characterizes deserts?
Very low precipitation.
What characterizes tropical forests?
Warm temperatures, heavy rainfall, high biodiversity, nutrient-poor soil.
What are the main freshwater biomes?
Lakes, rivers, and streams.
What are the main marine biomes?
Estuaries, coastal waters, and the open ocean.
What is an oligotrophic lake?
Low nutrients and high oxygen.
What is a eutrophic lake?
High nutrients and abundant organic matter.
What is upwelling?
The movement of cold, nutrient-rich water to the surface.
Why is upwelling important?
It supplies nutrients for phytoplankton.
What happens during El Niño?
Trade winds weaken, reducing upwelling.
How does El Niño affect primary productivity?
It decreases because fewer nutrients reach surface waters.