Lecture 21 and 22- ecosystem Flashcards
Define ecosystem.
the complex of a biological community
of interacting organisms and their physical
environment
What is Earth closed with respect to and open with respect to?
Open to energy
Closed to atomic matter
What energy drives processes that move material around the planet?
Energy from sun and radioactive decay that melts magma in the earth’s interior
What does the moon do?
Stabilizes the Earth’s tilt which influences climate
Produces ocean tides
Slows Earth’s rotation
What would happen to the composition of the atmosphere without living organisms?
Nitrogen, water and oxygen combine to make nitric acid (HNO3) which would dissolve in the ocean
What 4 compartments is the physical environment divided into?
Oceans, fresh waters, atmosphere, land
Where does most material that cycles through the 4 compartments end up?
In the ocean
Why do oceans respond slowly to input from other compartments?
They only exchange materials at their surface
Where do oceans recieve materials from the land?
In runoff from rivers
Why are concentrations of mineral nutrients very low in ocean waters?
Shallow ocean waters surrounding land mass mix very slowly with ocean waters, most material sinks to the seafloor.
How are some elements brought back to the surface near the coasts of continents?
Offshore winds push surface waters away from the shore, cold bottom water rises to the surface
What name is given to the rise of cold bottom water rising to the surface?
Upwelling zones
What do upwelling zones support?
High rates of photosynthesis and sense animal populations such as fisheries
What is the freshwater compartment comprised of?
Lakes, rivers, groundwater
How do nutrients enter fresh water?
some rain water
Most from weathering of rocks
What happens to mineral nutrients after entering rivers?
Carried rapidly to lakes or oceans, in lakes:taken up by organisms and incorporated into their cells
What happens when organisms die in water?
Sink to the bottom, taking nutrients with them
What does decomposition by detritivores do?
Consumes O2 in bottom water
How is the lack of O2 in bottom water and lack of nutrients in surface waters of lakes countered>
Vertical movements of water called turnover
What is an important agent of turnover in shallow lakes?
Wind
How do deep lakes in temperate climates have an annual turnover?
Driven by temperature- water is most dense at 4 degrees Celsius. Below that, it expands, so floats. Sun warms the surface in the summer, density is uniform throughout lake, modest wind mixes entire water column
What happens in deep lakes in temperate climates as summer progresses?
Surface water becomes warmer, depth of warm layer increases, thermocline is where the temperature drops abruptly.
What happens to deep lakes in temperate climates in autumn?
Another turnover event
What causes the turnover event in deep lakes in the autumn?
Cooler surface water is denser than warmer water below, so it sinks and is replaced by warmer water from below.
How often do arctic lakes turn over?
Once each year
Why do tropical and subtropical lakes have permanent thermoclines?
They never become cool enough to have uniformly dense water.
How do many tropical lakes stay oxygenated?
They are turned over periodically by strong winds
What does the atmosphere regulate close to the Earth’s surface?
Temperature
What is the composition of the major gasses in the Earth’s atmosphere?
- 08% nitrogen
- 95% Oxygen
- 93% Argon
- 03% CO2
What gases are found at trace levels in the Earth’s atmosphere?
Hydrogen, neon, helium, krypton, xenon, ozone, methane
