Living World

• An ecosystem is a natural system of interdependent and interrelated living and non-living components
• Living features of an ecosystem (BIOTIC) include the flora (plants) and fauna (animals / fish etc.). Non Living (ABIOTIC) include sunlight, temperature, rainfall, soil, rock, light & water
• Producers are plants and trees that use sunlight to produce their own food (autotrophs) through the process of photosynthesis
• Consumers are those that eat other plants and organisms to get energy
• Decomposers are fungi and bacteria that will break down plant and animal matter releasing nutrients into the soil
• Nutrient Cycle is the transfer of nutrients within an ecosystem. The nutrients released by decomposers return to the soil & are taken back up by plants which are eaten by consumers. Whenplants or consumers die, decomposers release nutrients back to the soil
• Herbivores are plant eating animals; carnivores are animals feeding on other animals and omnivores eat plants and other animals.
• The exchange of energy in an ecosystem is shown through a food chain which shows what eats what - e.g. grass - grasshopper - shrew - owl
• Energy is lost at each stage of a food chain / food web as not all parts of an organism are consumed (e.g. bones, feathers) and at each stage some energy is being used by individuals for life processes such as growth and respiration
• There are three nutrients stores within an ecosystem (i) soil (ii) litter and (iii) biomass and nutrients are cycled between them.
• The abiotic and biotic factors in an ecosystem are linked - for example soil provides the moisture and nutrients for plants to grow and provides a habitat for insects and micro-organisms. When these die they decompose and release nutrients back into the soil
• Parts of an ecosystem are interdependent and therefore a change in one part of an ecosystem can have a knock on impact on other parts - changes can occur naturally or due to human activity, occur at different scales and have short or long term impacts
• When grey wolves were re-introduced, this led to reduced grazing pressure due to wolf kills. Aspen trees regenerated (fewer herbivores) & beavers returned to the area stabilising river banks & less soil erosion and more tree cover - more habitat for songbirds
• Large scale ecosystems are known as biomes, each with a dominant type of vegetation and distinctive climates and characteristics
• Variations in biomes across the world are due to factors such as ocean currents, winds, distribution of land and sea, latitude and altitude all of which cause differences in temperatures and water availability which affects vegetation
• Tropical Rainforests are found near the equator because of the intense heat from the sun & the low pressure system with rising air leading to high levels of rainfall. All year round heat & moisture results in large amounts of plant growth & high biodiversity.
• Deserts are found at 30oN/S of equator because these are areas of high pressure - cooler air sinks resulting in a lack of cloud cover - enables ground to be intensely heated during the day but temperatures fall at night. High pressure results in dry conditions
• Tropical Rainforests are located around the equator and in between the Tropics of Cancer and Capricorn - e.g. Amazon Rainforest (Brazil) and Congo (Central Africa)
• Rainforests lack seasons with year round high temperatures (20-29oC). Rainfall totals are high all year (often over 2500mm/yr)
• All year round growth means trees are evergreen. Trees grow very tall with distinct layers - forest floor, shrub layer, under canopy, canopy and emergent trees
• Rainforests soils are heavily leached due to high rainfall. These are known as latosols which are acidic and poor in nutrients. Most nutrients are found in the litter layer on the surface, (thin layer due to rapid decomposition in the warm & wet conditions).
• Warm wet climate of the rainforest, enables rapid growth and means that decomposition is rapid, putting nutrients back into the soil quickly to be taken up by further growth
• Climate, plants and soil are all tightly linked through water and nutrient cycles. Changes to the ecosystem have a significant knock on impact on both
• Rainforests have a very high biodiversity (50% of all world's animal, plant and inset species are found in the rainforest)
• High biodiversity results from high levels of solar energy and rainfall (all year growth), a wide range of local habitats providing homes for many different species. It has been a stable isolated biome with a long evolution with species becoming highly adapted
• Drip tips allow heavy rain to drip off leaves, coping with heavy rainfall; leaves have flexible bases enabling them to turn towards the sun; wide buttress roots, support the base of tall trees; shallow roots quickly absorb nutrients from decomposition
• Lianas (woody creepers) are rooted to the ground, but use trees to grow up to the canopy to get sunlight and epiphytes live on branches high in the canopy to get sunlight and get nutrients and water from the air rather than soil
• Howler monkeys live in the canopy which is rich in fruit and berries and they have prehensile tails which enable them to grip and swing from branch to branch in the canopy.
• The Amazon rainforest in South America is the world's largest rainforest and can be found in a number of countries but 2/3 of the Amazon is in Brazil
• 17% of the Amazon has been lost in the last 50 years alone through deforestation (the cutting down of trees)
• Causes of deforestation include: Logging - trees cut and sold as timber - mahogany is a popular hard wood; Mineral extraction - e.g. iron-ore mine in Carajas, Brazil; energy production (HEP) - Belo Monte dam involved flooding thousands of acres of rainforest
• Road building - Trans-Amazonian highway runs through the rainforest, opening the rainforest to more exploitation; Commercial farming - cattle and soy bean has led to large levels of deforestation
• Rapid urbanisation in cities such as Sao Paulo has also seen resettlement schemes set up offering land to move to move from the city to the rainforest
• Global warming


  • Reduction in carbon sink
  • Release of carbon dioxide from burning for forest clearance
  • Increase in greenhouse gases contributing to climate change
• Loss of biodiversity


  • Destruction of habitats
• Reduced local rainfall levels


  • Reduction in evapotranspiration
• River pollution


  • Gold mining uses mercury which is poisonous and gets into the river ecosystem
• Soil erosion


  • Deforestation breaks the nutrient cycle
  • Lack of trees and roots to bind the soil
• Deforestation


  Conflict between developers and the indigenous people
• Rainforests are incredibly important for people & the environment. For the environment they act as a carbon sink, helping to regulate climate, cycling water and nutrients to maintain the local ecosystem and provide many habitats supporting a high biodiversity