Transcript Biome
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