PDS AP Environmental Science 8th Period 2010-11

On our chapter 5 test, question 35 talks about the sustained increase in the primary productivity of the environment and how the sheep would respond. I did not think that the population would increase and stay at a significantly larger number of sheep because I thought the environment would not be able to hold an extra 1,000 sheep when it was leveled out at around 1,500. Why was the environment able to just take in 1,000 more sheep? Wasn’t it already at its carrying capacity?

On our chapter 2 test I missed the question, “During succession, biodiversity is greatest in the…” I thought it was “late stage” because the longer some environment has been around, the more species will have had the chance to come live it in. It also takes a long time for some tress to grow so I thought the tree diversity would be greater during this stage too. Can someone please explain why it is not the late stage?

In class on Friday we discussed the water, or hydrologic, cycle.  The water cycle plays an important role in all of the previous nutrient cycles we have discussed in class.  The three largest reservoirs of water are, 1. Oceans, 2. Ice forms (glaciers/caps), and 3. Groundwater.  Although water makes up the majority of our planet, only 2.6% of water is fresh.  Ice caps and glaciers make up 1.984% of fresh water, groundwater makes up 0.592%, and lakes make up 0.0007%.  This means that less than 1% of water is available for drinking.

The Water Cycle:

Source: http://upload.wikimedia.org/wikipedia/commons/thumb/9/94/Water_cycle.png/320px-Water_cycle.png

This process is driven by the sun and the gravitational force that is present on Earth.  Most of the flux is a physical change.  The cycle starts with evaporation.  This is the process by which water changes into a gaseous form and moves up from oceans, lakes, ponds, rivers, and soil into the atmosphere.  Hotter temperatures and strong winds can speed this part of the cycle up.  Also, areas that are heavily vegetated will lose water slower than areas with less vegetation.  Another way that water gets into the atmosphere is by transpiration.  This is the process by which plants release water vapor through their leaves.  Also note that transpiration and evaporation naturally distill water.  Water makes its return from the atmosphere as precipitation.  This is what water is called when water vapor condenses and falls to the Earth in the form of rain or snow.  Precipitation is taken up by plants and animals, but the majority flows as runoff back into the oceans, streams, lakes, and ponds that it came from.  A portion of precipitation and surface water soaks down into the ground through soil and rock into aquifers, or underground reservoirs.  The upper level/limit of groundwater in an aquifer is known as the water table.  Aquifers can take thousands of years to refill fully after they are depleted.  Note that groundwater refers to the water actually under the ground in aquifers, not the water on the surface.  Also, note the equation for naturally acidic rain water : H2O + CO2=H2CO3 (Water + Carbon dioxide = Carbonic acid).

Human Impacts:

1. Damming of rivers to make reservoirs increases evaporation, and occasionally increases infiltration of the surface water down into aquifers.  It also decreases the flow of water downstream.

2. The overdrawing of wells leads to a depletion of groundwater.

3. Deforestation reduces transpiration and lowers water tables.

4. The pavement of roads blocks infiltration and increases runoff.

Helpful links:

http://techalive.mtu.edu/meec/module01/title.htm This reviews the water cycle and helps explain infiltration.

http://techalive.mtu.edu/meec/module06/title.htm This explains aquifers and infiltration in depth.

http://www.epa.gov/climatechange/kids/water_cycle_version2.html This explains the water cycle and some effects of global warming on it.

http://www.youtube.com/watch?v=YswL4dIDQuk Funny song about the water cycle.

http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/hyd/smry.rxml Summary of the water cycle.

Our biggest environmental problem is pollution.  The pollution from our cars, factories, etc. is burning a huge hole in our ozone layer, which in turn is increasing the temperature of the world.  This increase is leading to many problems such as the glaciers melting and the disruption of many ecosystems.