Wrap-up Natural Selection + Evolution… then… Energy Flow in the Global Ecosystem, PART I ES 100: October 6 th, 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? BasilosaurusAmbulocetusPakicetus Humpback

Today: Energy Flow in Earth Ecosystem Solar energy input imbalance  Climate Global climate  Biomes Biomes  Plant/Animal Adaptations

Reflected by clouds and atmosphere Reflected by surface albedo Solar Energy Budget Absorbed as heat Absorbed in photosynthesis Absorbed by atmosphere and clouds  chemical energy drives climate 

Weather vs. Climate Weather describes short term variability Difficult to predict Butterfly effect Lorenz Climate describes typical 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 Cold, long, snowy winters Warm summer Why the cone-shaped trees?

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  Hot or cold Natural selection: Convergent Evolution

Plant adaptation to hot environments: Physical Structure

Plant adaptations: Physiology Stomata must be open to take in CO 2 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 = C 4 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: Solar energy input imbalance  Climate Global climate  Biomes Biomes  Plant/Animal Adaptations NEXT: Local climate and micro-climates effect smaller scale vegetation patterns Ecosystems governed by: feedbacks, climate, biology