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Geography - Sustaining Ecosystems, Tropical Rainforests, Polar…

- - - - Producers - organisms that use sunlight energy to produe food
      - Consumers - organisms that gets its energy by eating other organisms (producers or other consumers)
      - Decomposer - organism that gets its energy by breaking down dead material, e.g. dead producers, dead consumers or fallen leaves
        e.g. Bacteria, fungi
        Returns nutrients to soil where they can be used by plants
    - - Small-scale ecosystem; Hedgerow ecosystem
        
        Bushes with berries are eaten by: Greenfly, sparrow, thrush
        
        Greenflies are eaten by ladybirds, spiders, sparrows and thrushes
        
        Ladybirds and spiders are eaten by sparrows and thrushes
        
        Thrushes and sparrows are eaten by Sparrowhawks
  - - - Reduced plant growth
        
        Fewer berries for birds in the winter
        
        Number of sparrows and thrushes fall
        
        Fewer birds for sparrowhawks to hunt, so number of sparrowhawks falls
    - - Fewer habitats for ladybirds, greenfly and spiders, so numbers fall
        
        Sparrows and thrushes have less to eat, so numbers fall
        
        Fewer birds for sparrowhawks to hunt, so number of sparrowhawks falls
- - - - Mammals tend to be small, e.g. kangaroo rats
      - Many birds leave during the hottest weather
- - - - Climate
        
        Temperature - Very cold
        Temperatures are usually below 10 deg C.
        Winters are normally below -40 deg C and can reach almost 90 deg C
        
        Rainfall and snowfall is low - no more than 500mm a year, which is mainly in the summer
        
        Clearly defined seasons: cold summers, even colder winters
      - Plants
        
        Types of plants
        Lichens and mosses - found on rocks, only plants that can survive closer to the poles
        Grasses - found on the coast where it is warmer. Most common.
        There are a few grasses and flowering plants on the coast where it's warmer
        Small, short trees and stubs - grow in warmer, sheltered areas
        
        Growth - Very few plants. Plants grow slowly and don't grow very tall.
      - Animals
        
        There are relatively few different species of animals compared with other ecosystems
        
        Examples of animals found in polar regions:
        Polar bears
        Penguins
        Marine mammals such as:
        Whales
        Seals
        walruses
- - - - Low rainfall - 800-900mm per year
      - Distinct wet and dry seasons
      - Temperatures are highest (around 35 deg C) just before the wet season and lowest (about 15 deg C) just after it
    - - Hot summers (up to 40C) and cold winters (down to -40C)
      - Receive 250-500mm precipitation each year, mostly in the late spring and early summer
  - - - Mostly grass, scrub and small plants, with a few scattered trees, e.g. acacia trees
      - Plants adapted to cope with low levels of rainfall
        
        Many have long roots to reach deep water or small, waxy leaves to reduce water loss
    - - Dominated by grasses and small plants. They have very few trees. Grasses often have roots that spread out wide to absorb as much water as possible
  - - - Home to lots of insects, including many species of grasshopper, beetles and termites.
        Larger animals include lions, elephants, giraffes, zebras and antelope
    - - Home to fewer animal species than savannah grasslands. Mammals include bison and wild horses, and rodents such as mole rats
- - - - Some species create a hard outer coating for protection
    - - Many fish have small bodies so that they can easily swim through and hide in small gaps in the coral
- - - - Mammals - foxes, squirrels
      - Birds - woodpeckers, cuckoos
      - Insects - beetles, moths
      - Fish - trout, salmon
  - - - Deciduous forests - have broad-leaved trees that drop their leaves in autumn (e.g. oak), shrubs (e.g. brambles) and undergrowth (e.g. ferns)
      - Forest-floor plants (e.g. bluebells) often flower in the spring before the trees grow leaves and block out the light
      - Coniferous forests - have evergreen trees (e.g. pine, fir) and an understory of grasses and low-growing plants. Trees are evergreen so they can make use of available sunlight all year round
- - - - Very little light covers forest floor
        
        epiphytes - plants that grow on other living plants and take nutrients and moisture from the air
      - Lots of epiphytes e.g. orchids and ferns
- - - - The water vapour condenses to form clouds, and then falls as rain
        
        Water flows from one place to another in various ways, and is also stored on land. It may be:
        
        Stored (and flows) in small channels
        
        Stored in ponds and lakes
        
        Intercepted and stored by plants
        
        Surface run-off
        
        Soaking into the ground and stored as groundwater
        
        Flowing through soil and rock
        
        Water eventually ends up back in the river or sea, and the cycle begins again
- - - - Many products, including rubber, coffee, chocolate and medicines, are sourced from the rainforest. Undiscovered species might give us new medicines and other new products
      - Hardwoods e.g. mahogany are widely used from furniture and building, and logging of hardwoods can contribute a huge amount to a country's economy
      - Rainforests provide opportunities for farming and mining if the vegetation is cleared
    - - Home to the highest diversity of animal and plant species on the planet
      - Rainforest plants absorb 0.7 billion tonnes of carbon dioxide from the atmosphere each year, which helps to reduce climate change
      - Rainfall is intercepted by the high density of vegetation - this reduces the risk of local flooding because the movement of water to rivers is slowed down
      - Reduces risk of drought/flooding in areas a long way away - this is done by storing water and releasing it slowly into the atmosphere; this helps to regulate the global water cycle
  - - - Greenhouse effect
        Land is often cleared using the slash-and-burn technique.
        Burning vegetation produces CO2
      - Reduction in soil fertility
        Without trees to intercept rainfall, more water reaches the soil.
        Nutrients are washed away so soil fertility is reduced
        Typically lose fertility in 3-5 years
      - Threat to wildlife
        Artificial fertilisers are added to improve soil fertility
        This is washed into streams, threatening wildlife
    - - Water pollution
        Mining of precious metals, e.g. gold, often requires heavy machinery and removal of trees.
        Toxic chemicals used to extract and purify the trees are washed into streams and rivers
        This kills wildlife and pollutes people's drinking water
    - - Soil Erosion
        With no trees to hold the soil together, heavy rain washes away the soil
        Eroded soil can enter rivers
        This silts up habitats that fish use for breeding
      - Natural disasters
        The removal of trees interrupts the water cycle
        Areas as a result can become very dry
        The risk of wildfires increases
        Risk of flooding in other areas also increases
      - Further development of rainforests
        This is as logging requires the building of new roads
    - - Tourists may scare wildlife
        e.g. causing nesting birds to abandon their young
      - They may also damage vegetation and leave behind lots of litter
      - If tourism is unregulated, a lack of infrastructure e.g. sewers can lead to pollution of waterways.
        In order to build infrastructure (e.g. roads and airports), vegetation must be cleared
- - - - Trees drop leaves all year round - constant supply of dead leaves and twigs falling onto the soil surface, forming a thick leaf layer
        
        This is quickly broken down to form humus which then gets mixed with the soil
        
        Layer of humus is thin because the high density, fast-growing plants quickly absorb the nutrients
        
        Nutrients are also leached - washed downwards - through the soil by heavy rainfall, making the soil nutrient poor
        
        Trees and other vegetation have roots close to the surface, where the nutrients are - there are lots of roots in the humus layer
- - - - For example, Agouti (a rodent) are one of the only animals who can crack open the hard seed pod of the Brazil nut to eat the nut inside. Sometimes, the agouti bury the nuts - these can sprout into new seedlings. If the agouti became extinct, the Brazil nut trees would decline, and so could all the other animals who live in or feed on the Brazil nut trees. People who sell Brazil nuts to make a living may also be affected