Transcript Variation in the Physical Environment / Biomes

Variation in the Physical
Environment /
Biomes
Lecture 2 (Ruesink)
Biology 356
Climate and vegetation patterns overlap
•Western WA
•Eastern WA
•AK
•CA
•HI/FL/Caribbean
•Today we focus on the causes of spatial
and temporal variation in the physical
environment, and on the vegetation
associated with different environments
•These are linked by adaptations of
organisms (first lecture)
Temperature
• The earth circles the sun every _______
• The earth is tilted relative to the sun
• Solar heating declines with latitude as
incident sunlight is spread across a larger
area
• Latitudinal pattern: Lower latitudes are
_________
• Seasonal pattern: Summer occurs at high
latitudes when ________________
Figure 4.1
Precipitation
• Solar heating causes air to rise
• Rising air cools, and moisture
condenses (precipitation)
• Hadley cells span 30 degrees latitude:
as air descends, it warms and
evaporates water
• Deserts occur at latitudes of ______
Figure 4.4
Figure 4.7
Winds
• Air lags behind the rotation of the earth,
lagging more where the earth spins faster
(low latitudes)
• The doldrums (intertropical convergence
zone, where air rises) occur at latitudes of
______
• Flying to Chicago is ______ than flying
back
• Surface flows are shifted toward the west
in the tropics, where air moves (towards/
away from) the equator.
Figure 4.6
Ocean temperature and
currents
• Water currents mimic wind patterns
• Water moving offshore causes
upwelling
• Ocean moderates climate
Test your knowledge
• How would you
expect
temperature
and rainfall
patterns to vary
seasonally
around the
equator?
Figure 4.8
Figure 4.3
ENSO
• El Nino-Southern Oscillation is an
example of temporal variation in
oceanic and terrestrial climate
•High pressure in Australia, low pressure in Tahiti (=
Southern Oscillation when this switches)
•Weak equatorial trade winds
•Strong subtropical winds blow West to East
•Warmer, low productivity water moves east, passing
Galapagos Islands and coast of Peru (El Nino)
•Damp weather, fishery crashes in western Americas
Figure 4.15a
Figure 4.17
•ENSO index is based on sea surface temperatures
Figure 4.15b
Many important biological phenomena are correlated
with ENSO (caused by similar climatic patterns)
Figure 4.16
Long term patterns of
climate change
• Reconstructed from stable isotopes in ice
cores
• Why does d18O indicate air temperature?
– Stable isotopes are natural (and often rare)
forms of elements that differ in number of
neutrons
– Heavier isotopes of oxygen condense more
easily (and drop out of the atmosphere in cool
temperatures before reaching the poles)
– Vostok ice core from Antarctica contains a
record of several hundred thousand years
Vostok, Antarctica
•Temperature record
is based on oxygen
stable isotopes: ratio
decreases by 1 ppt
for each 4oC
decrease in T
•CO2 record is simply
the concentration in
the atmosphere (gas
trapped in the ice)
Now
Then
Figure 4.18
Are organisms responding to
modern climate warming?
Track trends in the phenology of species.
Phenology = life history events, for instance,
migration timing, flowering, egg laying, hatch date
Physical characteristics of the
environment that affect plants
• Light
– In shade, larger leaves; species differ in their compensation
and saturation light levels (3.10)
• Nutrients
– Local increase in root density in high-nutrient environments
(3.8-3.9)
• Water
– C4 and CAM photosynthesis help conserve water inside leaves;
tension-cohesion helps plants collect water from soil; some
plants store water, or become dormant in low-water periods;
spines and hairs also help prevent water loss (3.3-3.7)
• Temperature
– Similar answers to above
• Carbon dioxide
– Similar answers to above, because CO2 enters leaves as H2O is
lost
Physical characteristics of the
environment that affect animals
• Temperature and Water
– Water conservation can occur through behavior and
through physiological retention (kangaroo rats don’t pee)
– Torpor, endothermy/exothermy, body size are all
adaptations to temperature conditions
– Countercurrent circulation helps conserve heat (3.22,
3.23)
– Some organisms have antifreeze (2.26)
• Salt balance
– Active transport of salt molecules across organism
boundary (3.12-15, 3.24)
• Oxygen
– Trachea in insects, circulatory system in many animals
(3.20, 3.21)
Biome concept
• Biomes are convenient abstractions
of variation in vegetation (dominant
plant forms) across the earth
Figure 5.13 See also 5.14-5.23
Plants are distributed across
environmental gradients
• Gradient in
vegetation =
gradual
transition
• Ecotone =
abrupt edge
between two
habitats
Vegetation gradients vs. Activity space
•Includes species
interactions
Terrestrial biomes reflect temperature
and precipitation patterns
• Use Walter climate diagrams to
understand where different biomes
appear on a temperatureprecipitation graph
• Walter climate diagrams show
temperature and precipitation, with
scales adjusted to indicate whether
water is in excess or in deficit
Annual precipitation (mm)
Figure 5.11
30
20 10 0
Average T
-10
Figure 5.9