BIOL 2306 – Living Planet (hybrid)
CONCEPTS FOR EPISODE 7 – Community in the Skies
I.
Characteristics of the atmosphere
A. Composition
- nitrogen (N2) - 78%
- oxygen (O2) - 21%
- argon - < 1%
- carbon dioxide (CO2) - 0.04%
- Water vapor (varies from near zero at poles and above deserts to
0.04% above warm tropics)
B. Stratification
1. Troposphere – 0 to 5 miles up
a. weather occurs in this layer
b. ozone in this layer is considered a pollutant
2. Stratosphere – 5 to 30 miles up
a. layer of ozone formed from interaction of oxygen and
UV sunlight
b. ultraviolet (UV) light damages living cells on earth
c. ozone layer absorbs UV light before it reaches the
earth’s surface, thus protecting cells
3. Mesosphere – 30 to 50 miles up
4. Ionosphere - > 50 miles up
aurora borealis (northern lights) and aurora australis
(southern lights) occur in this layer. When charged
particles from the sun interact with the atmospheric
gases at this level, bright colored flashes of light are
emitted.
II.
Greenhouse Effect
A. normal phenomenon that traps heat in the lower levels of the atmosphere
1. heat from the sun enters the earth’s atmosphere
2. heat strikes the earth’s surface
3. some heat is absorbed
4. some heat is reradiated back to the atmosphere
5. certain atmospheric gases (CO2, water, methane and others)
trap this heat, holding it close to the surface of the earth
a. CO2 and water are natural byproducts of aerobic
respiration as organisms burn nutrients (i.e. glucose)
for energy
b. Methane is a natural byproduct of anaerobic
(without oxygen) fermentation in guts of ruminants
(cows, deer) as well as decomposition by bacteria
B. this phenomenon makes life on earth possible – if it wasn’t occurring, the
planet’s surface would be too cold for life as we know it.
C. Global climate change
1. Two probable causes
a. normal cyclical variations in weather patterns
related to earth’s position relative to sun
b. anthropogenic enhancement of greenhouse effect
1) combustion: fossil fuels (gasoline, coal,
etc.) are burned to release energy
- water and CO2 are released as byproducts
- other byproducts pollute the air causing
acid rain which damages trees
2) deforestation:
- vegetation is burned to clear land and CO2
is released as byproduct
- when trees are removed, less CO2 is
consumed in photosynthesis
4) water pollution kills algae, decreasing CO2
consumed in photosynthesis
2. Effects
c. melting of ice (glacial ice and polar ice pack)
d. rising sea levels – coastal flooding and loss of land
mass
e. altered weather patterns - drought, flooding
f. altered habitat range for many species, extinctions
g. altered agricultural productivity
III.
Carbon cycle
A. CO2 is released to atmosphere by organisms during aerobic respiration
B. CH4 (methane) released to atmosphere by anaerobic bacteria and volcanic
activity accumulates in atmosphere as greenhouse gas
C. CO2 is removed from atmosphere by producers during photosynthesis
D. Producers die or are eaten by consumers
E. CO2 and CH4 returned to atmosphere as dead producers and consumers are
decomposed
F. CO2 is returned to atmosphere when wood or fossil fuels are burned
G. CO2 is returned to atmosphere when calcium carbonate skeletons of dead
marine organisms stored in limestone are dissolved by rain or broken
down by geologic processes
IV.
Water cycle
A. water enters the atmosphere when liquid water evaporates from surface
water and plants
B. water rises as sun heats air
C. as it rises, air cools and its ability to hold water decreases
D. water condenses into drops and falls as precipitation (rain, snow, sleet,
hail)
E. water hits the ground
1. some water infiltrates (soaks into soil)
2. if it cannot infiltrate, it runs off and enters nearest creek,
river, lake, and/or ocean
V.
Wing Structure
A. Insects
1. outgrowths of exoskeleton
2. most have two pairs of wings
3. coordination of flapping in figure-eight requires high level
of neural control
B. Birds
1. wings evolved from forelegs
2. feathers can slide over one another, changing wing shape
3. fingers fused for strength
C. Bats
1. wings evolved from forelegs
2. skin membranes stretched between fingertips, feet, and tail
3. elongated fingers for support
4. membrane also used to catch flying insects for food