The Nitrogen Cycle

Question 1

_______ is composed of __ percent of the atmosphere

Answer 1

Nitrogen, 78

Question 2

Enters the living world via free-living and symbiotic bacteria, which incorporate nitrogen into
their macromolecules through nitrogen fixation

Answer 2

Nitrogen

Question 3

Conversion of N2

Answer 3

Nitrogen Fixation

Question 4

Live in most aquatic ecosystems where sunlight is present; they play a key role in nitrogen fixation and are able to use inorganic sources of nitrogen to “fix” nitrogen.

Answer 4

Cyanobacteria

Question 5

Bacteria live symbiotically in the root nodules of legumes (such as peas, beans, and peanuts) and provide them with the organic nitrogen they need.

Answer 5

Rhizobium

Question 6

Free-living bacteria, such as __________, are also important nitrogen fixers.

Answer 6

Azotobacter

Question 7

is especially important to the study of ecosystem dynamics since many ecosystem processes, such as primary production and decomposition, are limited by the available supply of nitrogen.

Answer 7

Organic Nitrogen

Question 8

Process converts nitrogenous waste from living
animals or from the remains of dead animals into ammonium (NH4+) by certain bacteria and fungi.

Answer 8

Ammonification (tandaan mo nitrogenous to ammonium ayan na sagot oh mag isip k n lng)

Question 9

The ammonium is converted to nitrites (NO2−) by nitrifying bacteria, such as Nitrosomonas, through _____, Subsequently, nitrites are converted to nitrates (NO3−)by similar organisms.

Answer 9

Nitrification (NITRIfying, NITROsomonas ayan na clue mo oh) pag naging nitrItes na magiging nitrAtes

Question 10

Third, the process of _______ occurs, whereby bacteria, such as Pseudomonas and Clostridium, convert the nitrates into nitrogen gas, allowing it to re-enter the atmosphere.

Answer 10

Denitrification, kaya mo n yan

Question 11

True or False: Nitrogen enters the living world from the atmosphere via nitrogen-fixing bacteria.

Answer 11

True malamang

Question 12

True or False: This nitrogen and nitrogenous waste from animals is then processed back into gaseous nitrogen by soil bacteria, which also supply terrestrial food webs with the organic nitrogen they need.

Answer 12

True basahin mong mabuti

Question 13

Human activity can release nitrogen into the environment by two primary means:

Answer 13

• combustion of fossil fuels, which releases different nitrogen oxides
• and by the use of artificial fertilizers in agriculture, which are then washed into lakes, streams, and rivers by surface runoff.

Question 14

Atmospheric nitrogen is associated with several effects on Earth’s ecosystems including the production of acid rain_______ and greenhouse gas ________ potentially causing climate change.

Answer 14

• acid rain (as nitric acid, HNO3)
• greenhouse gas (as nitrous oxide, N2O)