the living world

• ecosystem 


  a community of plants and animals that interact with each other and their physical environment
• biomass 


  renewable organic material that comes from plants and animals
• biotic (living) examples:

  • fish
  • plants
  • frogs and toads
  • flowers
• abiotic (non-living) examples :

  • water
  • sunlight
  • oxygen
  • soil
  • rocks
• food chain 


  connections between different organism that rely upon one another as their source of food
• producer 


  an organism or plant that is able to absorb energy from the sun through photosynthesis. Also needs water, carbon dioxide and nutrients from the soil
• consumer 


  creature that eats herbivores and/or plant matter - they obtain the energy from what they eat
• decomposer 


  an organism such as bacterium/fungus that breaks down dead tissue, which effectively recycles their nutrients back to the environment
• the arrows in the food chain show the transfer of biomass from one organism to another - this is called trophic levels
• case study - Epping forest - small scale ecosystem in UK 


  20 species of dragonfly

  east London

  biodiversity in the deciduous forest remained high due to careful management
• the ecosystem at Epping

  large number of native tree species (oak, elm, ash)

  lower shrub layer at 5m, overlaying a field layer

  177 species of moss and lichen grow here

  many insect, mammal and bird species are supported here

  38 bird species

  700 species of fungi - important decomposers
• food web 


  producers - mosses, grasses, herbs, shrubs, deciduous trees

  consumers - badger, fox, small birds, insects
• how is the ecosystem interdependent

  most trees are deciduous (loose leaves in winter)

  maximise photosynthesis in summer - green leaves

  nutrient cycling - litter in autumn, gone by spring
• Epping forest nutrient cycle

  biomass large due to height of trees and dense undergrowth

  soil store large - always plenty of humus

  high flow rates between litter, soil and biomass reflect vigorous cycle of new growth that takes place yearly

  litter biggest in autumn
• managing Epping forest 


  paths for walking and riding are open for public use

  maintaining vegetation protects native deer population

  recreation controlled : car parks, visitor centre, rubbish bins, leaflets
• biomes 


  large scale ecosystems defined by abiotic factors (climate, geology, soils, vegetation)
• tropical rainforests 


  found along equator in Asia, Africa, South America - sunrays concentrated at this latitude, heating moist air which rises and leads to heavy rainfall and little seasonal variation

  creates perfect condition for evergreen rainforest
• deserts 


  found close to tropics of cancer and Capricorn

  air that rises over equator heads poleward after shedding its moisture as rain

  suns rays still heavily concentrated at this low latitude

  combined with dry air, brings arid desert conditions to places like the Sahara
• tropical grasslands 


  sandwiched between the 2 extremes of tropical grasslands and desert

  conditions are dry for half the year, due to the seasonal movement of the Hadley cell - limits growth of trees
• temperature grasslands 


  short tussock and feather grasses dominate the landscape between 40degrees and 60degrees north of equator, in drier centres of continents away from sea
• Mediterranean 


  drought-resistant small trees and evergreen shrubs grow between 30degrees and 40degrees north and south of equator, only on west coats of continents
• deciduous forests 


  grow in many places at high latitudes - sun rays are weaker so trees shed leaves in cooler darker winters
• coniferous forests 


  found at 60degrees north where winter temps are extremely cold due to lack of insolation, due to Earth's tilt, no sunlight for some months of the year at high latitudes, evolved needle leaves that reduce moisture and heat loss during cold darker winter months
• tundra (cold desert) 


  found around the Artic Circle, where suns rays have little strength, temps are below freezing for most of year, only tough short grasses can survive, often in waterlogged conditions
• tropical rainforests have an equatorial climate 


  temperature is high and constant throughout the year - concentration of sun's energy

  rainfall is high - heat from sun, creates rapid evaporation and transpiration
• convectional rainfall 


  ground warmed by sun

  air next to ground is warmed and rises

  rising air cools and condenses, forming clouds
• how plants have adapted to live in the tropical rainforest

  heat and humidity - using the circulating water as a sort of cooling system, having leaves that can cope with large amounts of water falling on them, passing water to soil or returning it to atmosphere

  competition for sunlight - most sunlight received by tops of tall trees, lowest layers rely on other ways of getting food supply - from soil or attaching themselves to a host tree or shrub
• how animals have adapted to living in the tropical rainforest

  competition for food - specialised and live off specific plant/animal that few others eat, some trees depend on animals to spread seeds of their fruit

  other survival strategies - camouflage, bright colours = poisonous
• physical characteristics of rainforest

  climate - equatorial, annual rainfall usually exceeds 2,500mm

  vegetation - renowned for rich vegetation, particularly trees (30-45m)

  soils - mainly thin and poor but so much vegetation because of rapid recycling of nutrients
• animals adaptions - tropical rainforest

  spider monkey - long, strong limbs to help it climb through the rainforest trees

  flying frog - fully webbed hands and feet, flap of loose skin that stretches between its limbs which allows it to glide from plant to plant
• deforestation 


  a process where natural forest or removing of trees - usually for the resource of wood
• effects of deforestation

  • reduce biodiversity
  • release greenhouse gas emissions
  • increase soil erosion
  • disrupts water cycle
• case study - the amazon

  • south America, covering countries mostly in the north - between the equator and tropic of capricorn
  • covers 2.1million square miles
  • 2nd longest river in the world
  • 1 in 10 species in the world lives within the Amazon rainforest
• causes of deforestation - commercial farming : cattle

  80% of tropical rainforest destruction in Brazil

  land cannot be used for long (quality of the pasture declines quickly) - cattle farmers have to move them on and destroy more land
• causes of deforestation - commercial farming : crops

  cleared to make way for vast plantation (e.g bananas, palm oil)

  soil will not sustain crops for long

  sugar cane used for biofuel is beginning to become a major crop
• causes of deforestation - road building 


  needed roads to bring in equipment and transport products to markets

  also makes it accessible to other exploiters of the rainforest

  the Trans-Amazonian highway began construction in 1972 and is 4000km - played important part in opening remote areas of rainforest
• causes of deforestation - settlement and population growth 


  all activities need workers, these workers and their families need homes and services - clear forests to build settlements for people to live
• causes of deforestation - logging

  timber companies interested in trees such as mahogany and teak - sell them to other countries to make furniture

  smaller trees often used as wood for fuel or made into pulp or charcoal

  vast areas cleared in one go - estimated 50% of deforestation is illegal - ignores environmental laws
• impacts of deforestation - global : global warming

  releases CO2 - tree canopy absorbs in atmosphere but is released when cut down

  fire often used in clearing rainforests - carbon stored in wood returns to atmosphere

  deforestation is a main contributor to greenhouse gas emissions - cause global warming
• impacts of deforestation - global : loss of biodiversity 


  individual species will become endangered and possibly extinct

  estimated 137 plant, animal and insect species are being lost daily due to rainforest deforestation - possible cures for diseases

  by 2030 Amazon could loose between 30-45% of main species