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Wrap-up Natural Selection +
Evolution… then…
Energy Flow in the Global
Ecosystem,
PART I
ES 100: October 6th, 2006
Does Natural Selection 
Evolution?
Defining ‘evolution’
Scientific Definitions:
• All the changes that have transformed life on earth from its
earliest beginnings to the diversity that characterizes it today
–Neil Campbell
• The origination of species of animals and plants
–O.E.D.
…
Common Usage:
• A process of continuous change from a lower, simpler, or worse
to a higher, more complex, or better state
–Merriam-Webster’s Dictionary
From a scientific point of view, evolution is just how new
species come about
Theory of Evolution: Criticisms
• Microevolution is generally accepted, but
macroevolution is hotly debated
– How does evolution add information to a genome to
create progressively more complicated organisms?
– How is evolution able to bring about drastic changes so
quickly?
– How could the first living cell arise spontaneously to
get evolution started?
Pakicetus
Ambulocetus
Basilosaurus
Humpback
Today: Energy Flow in Earth
Ecosystem
Solar energy input imbalance  Climate
Global climate  Biomes
Biomes  Plant/Animal Adaptations
Solar Energy Budget
Reflected by clouds and
atmosphere
23
albedo
100
8
Absorbed by
atmosphere and 20
clouds
57
2
47
drives climate 
Reflected by surface
Absorbed in photosynthesis
 chemical energy
Absorbed as heat
Weather vs. Climate
• Climate describes typical
• Weather describes
short term variability
• Difficult to predict
• Butterfly effect
• Lorenz
conditions for a region
• More predictable
• Global Climate:
• Hadley Cells
• Tilt + Orbit = Seasons
• Frontal Systems
 Biomes
• Local Climate:
•
•
•
•
mountains
oceans and lakes
latitude
elevation
• Micro-Climates
Uneven Heating of Earth
LATITUDE:
More Heat Energy at Equator than at Poles
•sun’s rays hit more directly
•less atmosphere to penetrate
Uneven Heating of Earth
LATITUDE:
More Heat Energy at Equator than at Poles
•sun’s rays hit more directly
•less atmosphere to penetrate
Hadley Cells: Heat Moves Air
What’s missing?
Biome: A large geographical region where plants have similar
physiological adaptations to the climate.
Another Energy Imbalance:
Orbit + Tilt = Seasons
Hadley Cells + Frontal Systems +Seasons
Biomes
=
What’s missing?
Biome: A large geographical region where plants have similar
physiological adaptations to the climate.
Biomes can be classified by
precipitation and temperature.
Boundaries are fuzzy (ecotones) !
Arctic Tundra:
 Short, intense
growing season
 Intense cold
 Strong winds
 Permafrost
 Low primary
productivity
 Slow
decomposition
Lots of C
held in soil
Boreal Forest
Why the cone-shaped trees?
•Cold, long, snowy winters
•Warm summer
Evergreen and deciduous
 Intermediate temperature
 Adequate moisture
 Few constraints on growth
High primary
productivity
Temperate Grasslands:
 Continental regions
- hot summer, low rainfall
 Fires
 Windy
Tropical Savanna Grassland
 Similar to Temperate
Grasslands
hot summer
moderate rainfall
 Fires
Deserts:
 North and south of tropics
 Dry
Natural selection:
 Hot or cold
Convergent Evolution
Plant adaptation to hot environments:
Physical Structure
Plant adaptations: Physiology
• Stomata must be open to take in CO2
• Open stomata = water loss
• How can a plant minimize water loss?
• Keep stomata closed as much as possible
• Open only at night = CAM plants
• Cactus, some epiphytes, succulents
• Open only a little bit = C4 plants
• Some grasses
Tropical rainforests:
 Near the equator
 Hot
 Moist conditions
 Fast Decomposition
 High primary
productivity
 Tight cycling of
nutrients- soils are
actually quite poor
Where is Santa Barbara?
Chaparral or Mediterranean-type
• Strong seasonality
• Hot, dry summers
• Mild, wet winters  high productivity
• Fires feed on large fuel supply
Most Rapidly Expanding Biome?
Summary:
Ecosystems governed by: feedbacks, climate, biology
Solar energy input imbalance  Climate
Global climate  Biomes
Biomes  Plant/Animal Adaptations
NEXT: Local climate and micro-climates effect
smaller scale vegetation patterns