Section B: The Living World

• An ecosystem is all the biotic and abiotic things in an area.
• Biotic things are living such as animals and plants.
• Abiotic things are non-living things such as rocks.
• Ecosystems are grouped as producers, consumers or decomposers.
• Producers

  • Example: Grass
  • Uses sunlight energy to produce food
• Consumers

  • Get energy from eating other organisms (producers or other consumers)
• Decomposers

  • Example: Bacteria and Fungi
  • Get their energy from breaking down dead material such as dead organisms
• The nutrient cycle shows how nutrients move through a ecosystem.
• The nutrient cycle shows how nutrients move through an ecosystem.
• The Nutrient Cycle

  1. When dead material decomposes, nutrients are released into the soil
  2. Nutrients are taken from the soil by the plants - the plant may then be eaten by consumers who will take in the nutrients
  3. When plants or consumers die, the nutrients return to the soil
  4. This transfer of nutrients is called the nutrient cycle
• Tundra

  • Found at high latitudes (above 60N) such as Northern Europe, Canada and Alaska
  • Winters are very cold, summers are brief and there is little rainfall
  • Few trees - vegetation includes mosses, grasses and low shrubs
  • Layer of permanently frozen ground called permafrost
• Boreal Forest/Taiga

  • Found between 50N and 60N
  • Winters are cold and dry, summers are mild and moist
  • Trees are coniferous - they are evergreen and have needles
• Tropical Rainforest

  • Found around the equator/between the tropics
  • Hot and wet all year round
  • Lush forest with dense canopies of vegetation forming distinct layers
• Hot Desert

  • Found between 15 and 35 north and south of the equator
  • Very little rainfall, very hot in the day and very cold at night
  • Shrubs and cacti are sparsely distributed in sandy soil
• Polar

  • Found around the north and south poles
  • Very cold, icy and dry
  • They remain dark for several months each year so growing season is very short (around two months)
• Temperate Deciduous Forest

  • Found mainly in the mid latitudes where there are four distinct seasons
  • Summers are warm, winters are relatively mild and there's rainfall all year round
  • Deciduous trees lose their leaves in winter to cope with the colder weather
• Savannah Grassland

  • Found between the tropics
  • Distinct dry and wet seasons although rainfall is still relatively low
  • Most of the vegetation includes grasses and a few scattered trees
• Temperate Grassland

  • Found at higher latitudes where there is more variation in temperature and less rainfall
  • No trees, just grasses
• Tropical Rainforest Climate

  • Same all year round with no definite seasons
  • Temperatures between 20-28C which only varies by a few degrees each year
  • High temperatures due to intense sun energy at the equator - the sun is overhead all year round
  • Rainfall around 2000mm per year as it rains every day
• Tropical Rainforest Plants

  • Most plants are evergreen to help them take advantage of the continual growing season
  • Many trees are extremely tall and dense meaning very little light reaches the forest flow
  • Lots of epiphytes ( plants that grow on other living plants, taking their nutrients and moisture from the air )
• Tropical Rainforest People

  • Many indigenous people have adapted to life in the rainforest
  • Making a living by hunting, fishing, gathering nuts and berries or farming
• Tropical Rainforest Soil

  • Soil is infertile as heavy rainfall washes the nutrients away
  • Surface nutrients from decayed leaf fall but the layer is very thing as decay occurs fast in warm, moist conditions
• Tropical rainforests are said to be home to more animal species than any other ecosystem.
• Biodiversity is the variety of organisms living in a particular area - both plants and animals.
• Biodiversity


  The variety of plant and animal life in a particular habitat
• Tropical Rainforests


  • Extremely high biodiversity
  • Contain 50% of the world's plant, animal and insect species
  • May contain half of all life on earth
• Tropical Rainforests


  • Stable and productive environments
  • Climate is constant
  • Plants and animals don't have to cope with changing conditions
  • There is always plenty to eat
• Many organisms have evolved to depend on other species for survival


  They are specific to a particular habitat or food source
• Deforestation and uncontrolled development of the rainforest


  • Likely to lead to the extinction of many species
  • Cause major loss of biodiversity
• Tropical Rainforests are independent ecosystems - all the parts of the rainforest are dependent on one another, if one changes everything is affected.
• Rainforests warm and wet conditions help fungi and bacteria grow on the forest flow where they will decompose dead plant material rapidly. This makes the surface soil high in nutrients aiding plant growth.
• In rainforests, plants pass on their nutrients when eaten by other animals. The dense vegetation provides lots of food so animal populations are high. When animals die, their nutrients are transferred back to the soil making it richer and encouraging more vegetation ( nutrient cycle) .
• Deforestation

  • Trees intercept and take up lots of water, releasing it back into the atmosphere for further rainfall.
  • Reducing tree coverage increases the risk of drought which would affect both the plants and animals in the ecosystem
• Deforestation

  • Tree roots stabilise the soil and provide nutrients when they drop their leaves
  • Fewer trees means the soil would have less protection from the heavy rainfall meaning the few nutrients left would wash away more easily. This would affect plant growth
• Layers of the rainforest

  • Forest floor/shrub layer - dark as most sunlight is blocked out + covered in a thick blanket of dead and decaying vegetation providing nutrients to surface soil + prone to flooding
  • Under canopy - shady and cool + limited sunlight so seedlings lay dormant until larger plants and trees die + lianas/vines take root int he ground and climb trees in an attempt to reach sunlight
• Layers of the rainforest

  • Canopy - continuous layer of trees averaging at 20-40 metres tall + habitat for most wildlife
  • Emergent layer - tallest trees in the rainforest growing up to 60 metres + trap more sunlight helping them make food to grow + supported by buttress roots which prevent them collapsing in high winds
• Layers of the forest: Shrub layer, Under canopy, Canopy and Emergent layer.
• A temperature of 27 degrees or above is required in the formation of tropical storms.
• Rising air means low pressure.
• Falling air means high pressure.