2.4

• Define biome

  Collection of ecosystems sharing similar climatic conditions
•  

  Outline the 5 different biomes in relation to limiting factors, productivity, biodiversity and provide a plant/animal example: Aquatic

  • Freshwater & marine

  Limiting factors

  • Water absorbs some light & limits photosynthesis
  • Deep oceans= no light for photosynthesis
  • Freshwater may freeze in temperature or polar winters

   

  Productivity

  • Tropical coral reefs=high
  • Deep oceans= very low
  • Temperate freshwater= moderate

   

  Biodiversity

  • Coral reefs= very high
  • Deep oceans= low
  • Temperature freshwater= moderate to low

   

  Plant & Animal example

  • Shark
  • Water lily
•   Forest

  • Tropical, temperate & boreal (taiga)

  Limiting factors

  • Nutrients locked in biomass instead of soils
  • High rainfall leeches nutrients from soils
  • Thin soils
  • Cold dry winters in temperate forests

   

  Productivity

  • Very high productivity in tropical rain forests
  • Temperate rainforests also high productivity but lower in autumn & winter

   

  Biodiversity

  • Very high
  • Tropical rainforests have highest diversity rate on Earth
  • Temperate forests have 2nd highest

   

  Plant & Animal example

  • Moose
  • Pine tree
•  

   Grassland

  • Tropical/savanna & temperate

  Limiting factors

  • Less precipitation than forest, but more than deserts
  • Seasonal temperature extremes limit productivity
  • Low decomposition & nutrient cycling

   

  Productivity

  • Moderate to low
  • Slow nutrient cycles & seasonal temperature extremes limit productivity for part of each year

   

  Biodiversity

  • High
  • Diverse in plant life
  • Soils rich in nutrients support extensive food webs
• • Desert
  • Hot & cold

  Limiting factors

  • Little precipitation
  • High evaporation
  • Extreme day/night temperature differences
  • Photosynthesis limited; low H20

   

  Productivity

  • Low
  • Water needed for photosynthesis
  • Soils may have good nutrients from minimal leeching

   

  Biodiversity

  • Low
  • Extremes of precipitation & temperature not optimal for plant/animal survival

   

   

  Plant & Animal example

  • Cactus
  • Lizards

   
• • Tundra
  • Arctic & alpine

  Limiting factors

  • Short days limit photosynthesis & productivity
  • Photosynthesis limited from frozen water in winter & saturated soils after thaw
  • Slow nutrient cycles

   

  Productivity

  • Low due to short days & low temperatures
  • Photosynthesis limited from frozen water in winter & saturated soils after thaw

   

  Biodiversity

  • Limited
  • Too cold for reptiles, amphibians, invertebrate, which are all cold-blooded

   

   

  Plant & Animal example

  • Arctic hare
  • Sedges

   

   
•  

  Outline the main factors which govern distribution of biomes

  Insolation

  • Amount of solar energy reaching earth's surface
  • Earth's tilt & rotation means more sunlight hits certain parts
  • Measured by amount of solar energy received per square cm per minute
• Outline the main factors which govern distribution of biomes

   

  Precipitation

  • P:E ratio
  • 1 when evaporation same as precipitation
  • 1 means rich & fertile
  • 1> too salty due to more evaporation, disabling plants from growing
  • >1 rains/snows so less evaporation; leaching in soil
•  

   

  Outline the main factors which govern distribution of biomes

  Temperature

  • Land & water absorb + retain heat differently
  • Usually measured in degrees Celsius
• Outline what the tricellular model of atmospheric circulation is

  • Equator receives more radiative heat from sun than poles
  • Explains distribution of this heat & precipitation
  • 3 cell pattern in northern & southern hemispheres
•  

  Explain how the Hadley cells work

  • Hadley cells:
  • At equator, warm less dense air rises
  • Spreads out towards poles
  • Gradually cooling & sinking before flowing back to equator
• Explain how the Ferrell cells work

  • Ferrell cells
  • Not driven by temperature
  • Flow in opposite direction to Hadley cells
  • Transports heat from equator to poles
  •  Result in semi-permanent areas of high & low pressure
• Explain how climatic zones work

  Climatic zones

  • Rising & descending parts of circulation cells give us climatic zones
  • Where air is rising, less pressure so more rainfall in these areas
  • Air is descending, higher pressure, less rainfall (desert)
•  

  Explain how polar cells work

  • Polar cells
  • Cold dense air flows at low levels North/south
  • Warms as it leaves poles & rises
  • Returns to poles at high levels
•  

  Discuss how the Hadley cell impacts the climate

  • Warm, moist air converging near equator causes heavy precipitation
  • Creates trade winds, tropical rain-belts & hurricanes, subtropical desserts & jet streams
  • Descending air is stable & dry
  • As air descends, low relative humidifies are produced- deserts
  • Seasonal variation due to fluctuations- dry & wet seasons of savannahs

   

   
• Explain how climate change is altering the distribution of biomes & causing biome shifts

  • Distribution of species determined by climate
  • Climate change shifts distributions
  • Increase in mean global temp & changes in precipitation causes biomes to move
  • Affects suitability of locales where species are found; threatens their survival

   
• State where biomes move due to climate change

  • Towards poles where it is cooler
  • Higher up mountains where it is cooler
  • Towards the equator where it is wetter
•  

  State 5 ways as to how climate change is affecting earth

  • Temp increase of 1.5-4.5 degrees Celsius by 2100
  • Greater warming at higher latitudes
  • More warming in winter than summer
  • Some areas are becoming drier, others warmer
  • Stronger storms
• State what a hotspot is

  • Areas predicted to have high turnover of species due to climate change
• State 5 examples of how climate change is impacting biomes

  • Himalayas- species can move no higher than the land mass
  • Equatorial eastern Africa- with very drought sensitive climate
  • Mediterranean regions- drought, high temperature
  • Madagascar- more extreme weather events
  • The north American great plains & great lakes

   
•  

  State what a hotspot is

  • Areas predicted to have high turnover of species due to climate change
•  

  State 5 examples of how climate change is impacting biomes

  • Himalayas- species can move no higher than the land mass
  • Equatorial eastern Africa- with very drought sensitive climate
  • Mediterranean regions- drought, high temperature
  • Madagascar- more extreme weather events
  • The north American great plains & great lakes
•  

  Define zonation

  • Change in vegetation community along environmental gradient
  • Appears in layers; diff zones have diff appearance
  • Can occur due to gradual change of abiotic factors

   
• State the reasons for zonation

  • Occurs due to changes in altitude, depth of water, tidal level, distance from shore etc
• •  

   

   

  Provide 5 examples of zonation

  • Spatial change
  • Environmental gradient
  • Horizontal bands/zones of animals & organisms
  • Vertical layers in rainforest
  • Differing plant communities as you go up a mountain
• State the 5 different factors which can characterise a niche

  • Temperature
  • Precipitation
  • Solar insolation
  • Soil type
  • Species interaction
•  

   

  Outline what succession is

  • Process of change over time in ecosystem
  • Predictable change  in vegetation community
  • Starts with pioneer community, then vegetation transitions through various intermediate communities to final climax community

   
•  

  Define primary succession

  • Occurs in areas with no life or soil
  • Colonisation of newly created land by organisms

   
•  

  Define secondary succession

  • Occurs when established ecosystem is destroyed
  • Faster because soil already present

   
• Outline the stages of succession

  Stage 1- Colonisation

  1. Bare inorganic surface
  2. Colonisation by pioneer species
  3. Typically r-selected species showing small size, short life cycles, rapid growth & production of many offspring/seeds
  4. Soil is shallow, nutrient poor & has erratic water supply
• Outline the stages of succession

  Stage 2- Establishment

  1. Species diversity increases
  2. Invertebrates increase humus (organic material) content & water-holding capacity
  3. Weathering of rock enriches soil with nutrients
• Outline the stages of succession

  Stage 3- Competition:

  1. Microclimate continues to change
  2. Larger plants increase cover & provide shelter, enabling K-selected species to become established
  3. Temperature, sun & wind are less extreme
  4. Earlier pioneer r-species can't compete with K-species for space, nutrients, or light  lost from community
• Stage 4- Stabilisation

  1. Fewer species colonise as late colonisers become established shading out early colonisers
  2. Complex food webs develop. K-selected species are specialist with narrower niches
• Stage 5- Climax community

  1. Stable & self-perpetuating. It exists in steady-state equilibrium
  2. Maximum possible development that a community can reach
•  

  Provide an example of succession: Hydrosphere

  • Succession in body of freshwater
  • Small lakes may disappear & and be replaced by plant communities
• Provide an example of succession: Halosphere

  Succession in saltwater marshes
•  

  Provide an example of succession: Psammosere

  • Succession along sand dunes
  • Stabilizes dunes & stops them shifting
• Provide an example of succession: Lithosere

  • Succession starting from bare rock
  • Seen on lava flows or after glacial movement
• Explain how productivity changes throughout succession

  • GP increase through pioneer stages
  • Decreases as climax community reaches maturity
  • Increase in productivity linked to growth & biomass
• Explain what different values of productivity: respiration ratio mean in relation to the stages of succession

  • P:R=1  means steady state (climax community)
  • P:R>1 biomass accumulates- middle stages, trees
  • P:R<1 biomass lost - early stages