Variation in the Physical Environment /

BiomesLecture 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

Figure 4.15a

•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 4.17

Figure 4.15b

•ENSO index is based on sea surface temperatures

Figure 4.16

Many important biological phenomena are correlated with ENSO (caused by similar climatic patterns)

Long term patterns of climate change

• Reconstructed from stable isotopes in ice cores

• Why does 18O 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 temperature-precipitation graph

• Walter climate diagrams show temperature and precipitation, with scales adjusted to indicate whether water is in excess or in deficit

Figure 5.11

30 20 10 0 -10 Average T

Ann

ual p

reci

pita

tion

(m

m)

Figure 5.9