Lab Exam Review for Biomes & Climate (Chapters 5 & 9)
Causes of global-scale patterns of species distribution:
Biomes & Biotic Provinces
While there is great diversity of life over the surface of the Earth, there are large areas that are (or appear to be) remarkably
similar
What are the causes of these large-scale patterns?
Historical geography —> Leads to large regions with similar evolutionary heritage (= Biotic Provinces)
Climate —> Leads to large regions with plants (& animals) that have similar adaptations (= Biomes)
Biotic Province:
A region inhabited by a characteristic set of taxa bound by barriers that tend to limit emigration & immigration of species.
Emphasizes history and evolutionary connections
Biotic provinces are shaped primarily by geological and evolutionary history
Continental Drift, caused by plate tectonics, has resulted in periodic unification and separation of continents
Unification —> genetic mixing
Separation —> geographic isolation & evolution of new species
Biome:
A large-scale community that is determined primarily by the physical environment (esp. climate)
Emphasizes the abiotic forces of nature in shaping ecosystems and communities of organisms
Terrestrial biomes are most strongly determined by climate
Rule of climatic similarity: similar environments favor organisms with similar form and functions
(but not necessarily similar evolutionary history)
Due to pressure & opportunities presented by similar physical environment (landscape, climate)
Weather vs. Climate (Chapter 9 pp 203-207)
Weather - A description of physical conditions of the atmosphere
Climate - A description of the long-term weather pattern in a particular area
The Great Weather Engine
Solar Radiation
Incoming solar energy at the top of the atmosphere averages about 1,330 watts/m3
About half is reflected or absorbed by atmosphere
Most solar energy reaching the earth is visible light
Energy re-emitted by the earth is mainly infrared radiation (heat energy)
Longer wavelengths are absorbed in the lower atmosphere, trapping heat close to the earth’s surface
(Greenhouse Effect)
Solar Radiation Drives Convection & Latent Heat Exchange
Lighter air rises and is replaced by cooler, heavier air, resulting in vertical convection currents
These currents transport energy and redistribute heat
Much of solar energy absorbed by the earth is used to evaporate water
Energy stored in water vapor as latent heat
If condensation nuclei are present, or if temperatures are low enough, condensation will lead to precipitation
Causes of Global Variation in Climate
Energy Balance
Solar energy is unevenly distributed
Sun strikes the equator directly all year
Earth’s axis is tilted
Energy imbalance is evened out by movement of air and water vapor in the atmosphere and by liquid water in rivers
and ocean currents
Convection Cells and Prevailing Winds
As air warms at the equator, rises, and moves northward, it sinks and rises in several intermediate bands, forming
circulation cells
Surface flows do not move straight North and South, but are deflected due to Coriolis Effect
Major zones of subsidence occur at about 30o north and south latitude where dry, subsiding air falls on continents, it
creates broad, subtropical desert regions
Jet Streams - Large-scale upper air flows
Generally follow meandering paths from west to east (6-12 km above surface)
Wind speeds are often 200 km / hr
Number, flow speed, location, and size all vary on a daily basis
Usually 2 main jet streams over North America:
Subtropical - (30o) north
Northern - Circumpolar vortex
During winter, the Northern Hemisphere tilts away from the sun and the atmosphere cools, pushing cold
polar air farther south
Terrestrial Biomes (pp 96-102)
Climate Factors & Characteristics
Biomes - Areas sharing similar climate, topographic and soil conditions, and roughly comparable communities
Temperature and Precipitation are among the most important determinants in biome distribution
Most terrestrial biomes are identified by the dominant plants of their communities
Global distribution of the major land biomes
Deserts
Characterized by low moisture levels and precipitation that is infrequent and unpredictable from year to year
Wide daily and seasonal temperature fluctuations
Soils are easily disturbed by human activities, and slow to recover
Plants exhibit water conservation characteristics
Grasslands
Communities of grasses, seasonal herbaceous flowering plants, and open savannas
Few trees due to inadequate year- round rainfall (rainfall is primarily in summer)
Large daily and seasonal temperature fluctuations
Frequent grass fires
Historic grazing by roaming herds of large ungulates
Subtropical Seasonal Forests / Savanna
Semi-evergreen and partly deciduous forests tending toward open woodlands and grassy savannas
Characterized by distinct wet and dry seasons with hot temperatures year-round
Mediterranean / Temperate shrublands
Characterized by warm, dry summers and cool, moist winters
Fires are a major factor in plant succession
Referred to as Chaparral in California
Biodiversity hotspot
Broad Leaf Deciduous Forest
Temperate regions support lush summer plant growth when water is plentiful
Deciduous leaves an adaptation to freezing temperatures
Eastern half of US was covered with broad leaf deciduous forest when European settlers arrived Much of that was
harvested a century ago for timber
Now large areas have re-grown and are again approaching old-growth status
Tropical Rainforests
Humid tropical regions support one of most complex and biologically rich biomes
Ample rainfall and uniform temperatures
Cloud Forests - High mountains where fog and mist keep vegetation continually wet
Tropical Rainforests - More than 200 cm annual rainfall with warm-hot temperatures year-round
90% nutrients tied up in living organisms
Rapid decomposition and nutrient cycling
Thins soil cannot support continued cropping, and cannot resist erosion
Conifer Forests
Cone-Bearing trees, somewhat low diversity
Plants reduce water loss by evolving thin, needle-like evergreen leaves with thick waxy coating
Can survive harsh winters & droughts and accomplish photosynthesis even under poor conditions
Fire often plays role in maintenance
Boreal Forest - northernmost conifer forest of North America & Eurasia
Broad band of mixed coniferous and deciduous trees between 45° and 60° N latitude
Moist and cool climate with abundant streams and wetlands
Montane Coniferous Forests - common in drier mtn ranges of North America & Eurasia
Cold temperatures, heavy winter snow, and dry summers
Tundra
Treeless areas with Very short growing season, with cold harsh winters (Damage slow to heal)
Arctic Tundra exhibits low productivity, diversity and resilience
Alpine Tundra receives intense solar radiation, hot summer ground temperatures, and potential droughts
AQUATIC ECOSYSTEMS
Saltwater ecosystems cover vastly more total area and contain much greater volume of water than all freshwater bodies
combined.
Oceans hold bulk of world’s water.
Aquatic ecosystems are influenced by local characteristics of climate, soil, and resident communities, and also by
adjacent terrestrial ecosystems.
Critical Aquatic Characteristics
Dissolved Substances
Suspended Matter
Depth
Temperature
Flow Rate
Bottom Characteristics
Internal Convective Currents
Connectivity to Other Aquatic Ecosystems
Vertical Component
Vertical stratification is an important aspect of many aquatic ecosystems.
Organisms tend to form distinctive vertical sub-communities.
Benthos - Bottom sub-community.
Low oxygen levels
Thermocline - Distinctive temperature transition zone that separates warm upper layer and deeper cold layer.
Estuaries
Estuaries - Bays or semi-enclosed bodies of brackish water that form where rivers enter the ocean.
Usually carry rich sediments.
Fan-shaped sediment deposit (delta) formed on shallow continental shelves.
Wetlands
Land surface is saturated or covered with water at least part of the year.
Swamps - Wetlands with trees
Marshes - Wetlands without trees
Bogs and Fens - Waterlogged soils that tend to accumulate peat.
Water usually shallow enough to allow full sunlight penetration.
Trap and filter water, and store runoff.
Coastal
Barrier Islands - Low, narrow, sandy islands that form offshore from a coastline.
Protect inland shores from surf.
Prized for human development.
Loss of vegetation triggers erosion.
Coral Reefs - Accumulated calcareous skeletons of colonial organisms (coral).
Depth limited by light penetration.
Among most endangered communities.
Barrier Islands
HUMAN DISTURBANCE
By some estimates, humans preempt about 40% of net terrestrial primary productivity.
Temperate broad-leaved deciduous forests are the most completely human-dominated biome. Tundra and Arctic
Deserts are the least disturbed.
About half of all original wetlands in the US have been degraded over the past 250 years.
LANDSCAPE ECOLOGY
Landscape Ecology - The study of reciprocal effects of spatial patterns on ecological processes.
Spatial patterns shape, and are shaped by, ecological processes occurring in them.
Considers humans an element of most landscapes.
Few places, if any, are devoid of human impacts.
Patchiness and Heterogeneity
Landscape ecologists claim all landscapes consist of similar mosaics of discrete, bounded patches with different biotic
or abiotic composition.
Predominate cover type acts as a matrix in which other patch types are embedded.
Landscape heterogeneity can exist across a wide range of scales.
Landscape Dynamics
Boundaries between habitat patches are considered significant.
Dynamics between patches may be of greater importance than processes within each patch.
Departs from classic ecological focus, and aligns with conservation biology.
RESTORATION ECOLOGY
Restoration Ecology - Seeks to repair or reconstruct damaged ecosystems.
Restoration - Active manipulation to re-create species composition and ecosystem processes as close to predisturbance state as possible.
Rehabilitation - Attempt to rebuild ecological structure or function without necessarily achieving original
conditions.
Restoration Ecology
Remediation - Cleaning chemical contaminants from a polluted area by physical or biological methods.
Living organisms are highly effective cleaning agents for many contaminants.
Reclamation - Chemical or physical manipulations of severely degraded sites.
Historically - irrigation projects to transform wetlands and deserts into agricultural production.
Restoration Ecology
Re-creation - Attempts to construct new biological communities on a severely disturbed site where basically
nothing is left to restore.
Mitigation - Developers and government agencies are often required to mitigate damage caused in one area by recreating a comparable biological community somewhere else.
Restoration Ecology Questions:
Is the best strategy to avoid destruction in the first place, or is nature a simple social creation to be molded ?
Under what conditions can / should we walk away let nature heal itself ?
What role should community / plant authenticity place in restoration ?
Which historic state should an area be restored to ?
ECOSYSTEM MANAGEMENT
Ecosystem Management - Attempts to integrate ecological, economic, and social goals in a unified systems approach.
Most resource agencies (Federal and state) are attempting to identify endangered landscapes and implement ecosystem
management as their guiding policy.
Turning away from commodity production and commercial / recreational resource use as top priority.
Ecosystem Management Critiques
We do not understand ecosystems in the detail necessary to manage them as single entities.
In developing countries, immediate needs of the poor will hamper enforcement of environmental protection.
Preservation / Management
Summary:
Terrestrial Biomes
Aquatic Ecosystems
Human Disturbance
Landscape Ecology
Restoration Ecology
Ecosystem Management
Global-scale patterns:
Realms & Biotic provinces
A. R. Wallace suggested a global division into 6
realms based on characteristic features of animals.
Key feature of classification is the similarity of animals of many taxa within a realm based on evolutionary
relationships
Certain dominant taxa (orders/families/genera) in each realm
Similar roles (niches) in different realms filled by different genetic stocks
Fig 8.2a The main biogeographic realms for animals are based on genetic factors.
Fig 8.3 The major vegetation realms are also based on genetic factors.
Part 2: Biodiversity
• Genetic diversity - variety of different versions of the same genes within a species
• Species diversity - number of different kinds of organisms within an ecosystem
• Ecological diversity - complexity of a biological community (number of niches, trophic levels, etc.)
Biodiversity Hotspots
Part 3: How do we benefit from biodiversity?
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Food
Drugs and medicines
Ecological benefits
Aesthetic and cultural benefits
Fig. 5.21
Part 4: What Threatens Biodiversity?
Extinction - the elimination of a species
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Natural process - one species lost every 10 years
Process been accelerated by human impacts on populations and ecosystems
E.O. Wilson - we are currently losing thousands of species a year
Part 5: Human-Caused Reductions in Biodiversity
Habitat destruction and fragmentation
Hunting and fishing
Commercial products and live specimens
Predator and pest control
Exotic species introduction
Diseases
Pollution
Genetic assimilation
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Hunting and fishing laws
The Endangered Species Act (ESA)
Recovery plans
Reintroductions
Minimum viable population
Private land and critical habitat
Reauthorization of the ESA
International wildlife treaties