People and the Biosphere

• The Malthusian Theory states that population growth will eventually outstrip food supply, resulting in famine and societal collapse.
• an ecosystem is a grouping of plants and animals that interact with each other and their local environment
• the biosphere is the layer of living things on earth, including animals and plants
• what is a biome? 


  a large ecosystem - plants and animals over a large area
• taiga biomes are at higher latitudes where the sun's rays are weak. trees are adapted to the cold with needle-like leaves. soil is thin and acidic as needles take a long time to decompose. animal diversity is low as it's difficult to adapt.
• temperate forests have 4 seasons, 1000-1500mm of annual rainfall, nutrient rich soil, deciduous trees, moderate animal populations
• deserts have hot days and cool nights, little precipitation (less than 250 mm/year), sandy soils, sparse vegetation, few animals
• rainforests have high humidity, high temperature, dense canopy, lots of plant species, diverse fauna, slow decomposition rate due to lack of oxygen
• grasslands have warm summers and mild winters, high temperatures during summer, moderate rainfall, grasses dominate
• biotic factors are living - fauna and flora
• abiotic factors are non-living - soils, rocks, water, the atmosphere
• tropical rainforests have no seasons, temperature stays between 21-30 degrees celsius, high rainfall (2000mm anually in the amazon rainforest), nutrient poor soil due to rainfall, infertile soil, interdependence between plants (epiphytes), high biodiversity
• abiotic and biotic factors impact each other - biological weathering, water availability impacts what plants can grow and where, soil type impacts plant growth, dense vegetation means nutrient rich soil which means biodiversity
• the tundra biome is found in the northern hemisphere and is characterized by cold temperatures and low precipitation
• the desert biome is found near the equator and is hot and dry
• local factors - altitude (higher altitude = lower temperature), rock and soil type can affect what plants grow, drainage (bad drainage means more flooding, plants have to adapt)
• food from the biosphere - fish and meat, sustainable harvesting of fruit and nuts, natural vegetation can be replaced with crops
• medicine from the biosphere - periwinkle plant used to treat leukaemia, aloe plant has soothing properties, poppies are the source of painkiller morphine
• fuel resources from the biosphere - animal dung is burnt as fuel, wood, biofuels convert plant products into fuel (bioethanol made from fermenting crops like sugarcane)
• building materials from the biosphere - straw used for roofing, animal dung mixed with clay and straw to make bricks, timber comes from trees
• biosphere services - regulates gases that make up the atmosphere (plants absorb carbon dioxide and produce oxygen), keeps soil healthy (new nutrients provided by rotting plant material), regulates water cycle (plants slow flow of rivers and filter water)
• resource demand - the amount of resources required to satisfy the needs of a population
• reasons for resource demand - urbanisation, food production, water shortages, affluence
• Boserup population theory - humans will develop over time and create new methods of harvesting food to satisfy the growing population