The living world

• Ecosystems vary in size and scale
• Small ecosystem


  Garden pond
• Large scale ecosystem


  All tropical rainforests - this is known as a biome
• Biodiversity


  The variety of plant and animal species within an ecosystem
• Interdependence


  Changes in one component can have significant impacts on other parts of the ecosystem
• Components of a food chain

  • Producers
  • Primary consumers
  • Secondary consumers
  • Tertiary consumers
• Decomposers


  Fungi and bacteria that help to return energy/nutrients back to the soil, break down dead organic matter, and release energy from organic matter so it can be recycled
• Food chains show the feeding interactions and transfer of energy from one organism to the next
• Food webs show the complex variety of plants and animals which feed on each other
• Deciduous woodland is an example of a small-scale ecosystem in the UK
• Components of a deciduous woodland ecosystem

  • Producers: Tree species, other plants, lichens, mosses
  • Primary consumers: Insects, rabbits, deer, squirrel
  • Secondary consumers: Frogs, voles, fox, badgers
  • Tertiary consumers: Foxes, birds of prey
• Animals can be in more than one trophic level
• Deciduous trees lose their leaves covering the ground with a thick layer which then decomposes adding nutrients to the soil
• Ash dieback has impacted over 1000 species dependent on ash trees in the UK
• Ecosystem balance


  A stable ecosystem is one where all the biotic and abiotic components are in balance so that the populations remain constant
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• Factors affecting ecosystem balance

  • Natural events: Wildfires, climate change, spread of invasive species, disease, extreme weather
  • Human activities: Deforestation, hunting, introduction of invasive species, hedgerow removal, changes to water supply/drainage, addition of chemicals
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• Biome


  A large-scale ecosystem
• AQA GCSE Geography
• Factors affecting biome distribution

  • Latitude
  • Precipitation
  • Altitude
  • Continentality
  • Ocean currents
• 2.2 Tropical Rainforests
• Contents


  • 2.2.1 Tropical Rainforest Ecosystem
  • 2.2.2 Deforestation
  • 2.2.3 Causes & Impacts of Deforestation
  • 2.2.4 Management of Tropical Rainforests
• Characteristics of biomes


  • Tropical rainforests
  • Tropical monsoon forests
  • Mediterranean
  • Deciduous forests
  • Coniferous forests
  • Savannas
  • Temperate grasslands
  • Deserts
  • Polar/tundra
• Hot Desert Ecosystem


  • Characteristics of Hot Desert Regions
• Location of hot desert climates

  • 15°- 30°north and south of the equator (tropical and sub-tropical)
  • North Africa - Sahara, Southern Africa - Kalahari and Namib, Australia. Middle East
• Annual Precipitation


  • Below 250mm
  • When rainfall does occur, it is often short torrential downpours
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• Temperature Range


  • Daytime temperatures can reach 50°C but average around 25°C
  • Night-time temperatures below 0°C
  • Diurnal range is large up to 45°C
  • Annual range is around 15°C
• Seasons


  Summer and winter
• Humidity


  Low often between 10−30%
• Soils


  • Tend to be saline - evaporation draws salts to the surface (salinisation)
  • Thin, sandy, grey and rocky
  • Contain little organic matter
  • Not very fertile
• Biodiversity


  • Low biodiversity - 5000−6000 plant species, many invertebrates and up to 20 species of bird
  • Plants include cacti, yucca
  • Animals include spiders, scorpions, camels, lizards
• Tropical Rainforest Ecosystem


  Characteristics of a Tropical Rainforest
• An example of a climate graph for a typical hot desert region
• Factors influencing the hot desert climate

  • High pressure all year which means the air is descending and warming so precipitation does not occur because the air is not rising
  • Prevailing winds are often from over land masses which means they contain little moisture
  • Some deserts are in a rain shadow so there is little rainfall
  • Cold ocean currents on the west side of continents may reduce summer temperatures due to the cooling effect of the ocean
• Influence of pressure systems

  1. Air rises at the equator and when it reaches the upper atmosphere it moves north and south

  2. The air cools and starts to sink

  3. This creates a zone of high pressure at about 30° north and south of the equator

  4. Due to the sinking air, warm air cannot rise, condense and form clouds, resulting in high aridity
• Distribution of the equatorial climate

  • The tropical rainforest (TRF) biome is mainly found in a band between 15°north and 15°south of the equator within the equatorial climate zone
  • Covering only 6% of the Earth's surface the main areas of tropical rainforest ecosystem are in the following countries: Amazon which is the largest remaining rainforest on Earth usually associated with Brazil but covers parts of seven other countries
  • Central America including parts of Belize, Costa Rica, El Salvador, Guatemala, Honduras, Nicaragua, and Panama
  • Central Africa including Cameroon, the Central African Republic, the Republic of Congo, the Democratic Republic of Congo (DRC), Equatorial Guinea and Gabon
  • Indo-Malaysia, including Malaysia, Indonesia and a number of other countries in South-East Asia
• Humans


  • The edges of the desert are used for livestock herding
  • Communities such as the Bedouin are nomadic
  • Live in large open tents made from fabric woven from camel hair and vegetable fibres
  • Food sources are mainly from the animals that the Bedouin herd - goats and cattle
  • Headwear is worn to protect against the heat of the sun and sand
  • Restrictions on movements due to international borders have affected the Bedouin lifestyle
  • Many Bedouin are no longer nomadic and live in permanent settlements