Quiz 3 Ecology

Limnetic zone

________- where sunlight does not penetrate to the bottom (horizontal)

Epilimnion

________: warmest, highest dissolved oxygen.

Hypolimnion

________: coldest, lowest dissolved oxygen (due to high biological oxygen demand (BOD) by decomposers)

Lignin

________: fills in spaces in cell wall.

Ecosystems

________ depend on the recycling of chemical elements.

Ammonium nitrate

NH4NO3 granules applied to soils (explosive)

Littoral zone

from shore out toward center, as far out as sunlight penetrates to the bottom

Euphotic zone

where there is sunlight

Aphotic zone

where there is no sunlight

Metalimnion

rapid temperature change

Hypolimnion

coldest, lowest dissolved oxygen (due to high biological oxygen demand (BOD) by decomposers)

Mississippi River

10th order

Amazon River

12th order

Straight

stream order 1-3, small headwater streams

Meandering

stream order 4-6, mid-reach streams

Braided

stream order 7-12, large, low-gradient rivers

Nitrogen fixation converts atmospheric nitrogen gas (N2):

to ammonia or ammonium (NH3 or NH4)

Nitrogen Fixation done by?

Some bacteria and by lightning converting ammonia in turn, Ammonia can then also be converted to nitrite (NO2-), and nitrate (NO3-) which plants can use

Phosphorus Cycle

· No atmospheric pool

· Most in mineral deposits and marine sediments

o Much of this in forms not directly available to plants

· Slowly released in terrestrial and aquatic ecosystems via weathering of rocks

· Usable form: dissolved inorganic phosphate

Effects of Human Activities on Phosphorus Cycles

· Remove large amounts of phosphate from the earth to make fertilizer

· Reduce phosphorus in tropical soils by clearing forests

· Add excess phosphates to aquatic systems from runoff

Only ______ nitrogen (ammonia; NH3) is usable by plant

Fixed

Decomposition takes place in steps

1. Scavangers (ants, flies, vultures, hyenas)

2. Bacteria, fungi

Lentic waters are fromed by?

Glacial, river, tectonic, and volcanic activity

Changes that occur longitudinally

• Increase in size (width and depth)

• Increase in volume (as tributaries flow in)

• From steep gradient to low gradient (flatter land)

Floodplain:

flat land adjacent to a stream or river that experiences occasional or periodic flooding

Flood magnitude:

• defined in terms of return period, or recurrence interval

  • E.g 100yr flood

• Just an average, based on historic data

• Can have back-to-back 500yr floods