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
What is the lowest level of the atmosphere?
Troposphere
What % mass does the troposphere make up?
80%
How high is the troposphere?
17km in tropics/subtropics
10km at higher latitudes
What layer is above the troposphere?
The stratosphere
How high does the stratosphere extend?
50km above the Earths surface
Where do most materials enter the stratosphere?
The intertropical convergence zone, where air is headed by the sun and rises to high altitudes
Where did the ozone hole develop?
Southern hemisphere
What would the average temperature of the Earth’s surface be if there was no atmosphere?
-18 degrees celsius, compared to current 17
Why is Earth warm?
Transparent to visible
Certain gases trap heat- green house gasses.
How much of the Earth’s surface is above sea level?
1/4th
Why does regional/local deficiencies of particular elements affect ecosystem processes on land?
Elements move slowly and only over short distances.
How is the terrestrial compartment connected to the atmospheric compartment?
By organisms that take chemical elements from the air
What does the type of soil in an area depend on?
The type of underlying rock from which it forms, as well as climate, topography, organisms and length of time
Why are old soils less fertile than new soils?
Nutrients leach out over time
How much of the solar energy arriving at Earth is captured by photosynthesis?
5%
What is the rate at which energy is incorporated into the bodies of photosynthetic organisms called?
Gross primary productivity (GPP)
What is the accumulated energy of photosynthetic organisms called?
Gross primary production
What is the energy available to organisms that eat primary producers called?
Net primary production (NPP)
What is NPP equal to?
Gross primary production- energy expended by primary producer during their metabolism
What do human activities modify?
The flow of energy
What human activities decrease net global primary productivity?
Converting forests to grasslands and urban developments
What human activities increase net global primary productivity?
Intensifying agriculture
How do humans increase energy flow?
Using solar energy
How much of the average annual net primary production on Earth do humans appropriate?
20%
What are biogeochemical cycles?
The movements of elements through organisms to the physical environment and back again
What does water do?
Movement transfers chemical elements between atmosphere, land, freshwater and oceans
What does fire do?
Powerful agent that speeds the cycling of chemical elements.
What is the movement of water through oceans/atmosphere freshwater and land called
Hydrological cycle
Why does the hydrological cycle operate?
Because more water is evaporated from the surface of the oceans then is returned by precipitation
What are the three largest rivers?
The amazon, congo, Yangtze
Why do rivers play a disproportionate role in the hydrological cycle compared with their volume?
Water spends a very short average time in rivers compared to the ocean
How have humans effected the temporal and spatial distribution of fresh water on Earth?
By building reservoirs and dams
What is a major consequence of human activities and water?
More water evaporates from land than before the industrial revolution
What are underground pools of groundwater called?
Aquifers
What is happening to groundwater because of humans?
It is being depleted, primarily by pumping it for irrigation
What will happen if current water consumption patterns continue?
By 2025, 3.5billion people will have inadequate water supplies
What elements are vaporised by fire?
Nitrogen, selenium, sulfur
What % of Earth’s annual CO2 production is caused by biomass burning?
40%
What does the rate at which CO2 moves from the atmosphere to the ocean depend on?
Photosynthesis by phytoplankton in surface waters by removing carbon from the water
Calcium carbonate shells (CaCO3)
Why is the North Atlantic an important carbon sink?
Because of the ocean conveyor belt
What drives the ocean conveyor belt?
Sinking of dense, saline water between greenland and europe
What evidence shows that the Earth was warmer when CO2 concentration was higher?
Air trapped in Antarctic and Greenland icecaps.
What does climate warming increase?
The rate of metabolism of plants and soil organisms- respiration returns CO2 to the atmosphere.
What may happen to diseases if temperatures rise?
Diseases may proliferate- cold used to kill off pathogens
Give an example of warmer temperatures leading to proliferation of disease.
Dengue fever and its mosquito vector are moving northward. Several plant diseases are also increasing their range northward.
What is also allowing people and diseases to spread more rapidly?
increasingly mobile and interconnected global community
Give an example of disease spreading rapidly due to mobile, interconnected global community.
the SARS (Severe acute respiratory syndrome) virus quickly spread from China to Canada
