GCSE Geography

GCSE Geography A - The Living World


Nutrient Cycle

Ecosystem - a system of links between flora and fauna and the natural environment in which they live

Nutrient Cycle
How substances that provide energy and sustenence to living organisms circulate around an ecosystem

  • Weathered rock and soil releases nutrients stored
  • Plants absorb nutrients through their roots
  • Animals and insects gain nutrients by consuming plants or other animals
  • When plants and animals die, they are broken down by decomposers
  • This forms detreitus which goes back into the humus in the soil
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Water Cycle

Water Cycle

  • When is rains, all water is diverted to the soild by the drip tip leaves of plants
  • The water leeches the soil of its nutrients
  • Is it quickly absorbed by the roots of plants
  • In hot tempratures, water from the ground is evaporated back into the air
  • Water is also lost from leaves through transpiration via the stomata cells on the underside of green leaves
  • The water vapour in the air rises to form clouds, then condenses to form rain again, and the cycle is complete.

This is called convectional rainfall.

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Food Chains

  • Producers (plants)
    convers solar energy into glucose by photosynthesis, e.g. oak tree
  • Primary consumers (herbivores)
    eat the producers e.g. caterpillar
  • Secondary consumers (carnivores)
    eat the primary consumers e.g. blue ***
  • Tertiary consumers (carnivores)
    eat carnivores and herbivores, and are eaten by nothing e.g. fox

They all die and are decomposed back into the soil, and provide nutrients which enables new producers to grow.

  • Scavengers - organisms that consume dead animals or plant e.g. maggots
  • Decomposers - organisms that break down dead animal or plant material e.g. bacteria
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Human Modification

Human Modification - the way in which humans interfere with the balance of an ecosystem

1) The removal or introduction of a new plant or animal into an ecosystem can:

  • Decrease the population of the organism upon which this feeds
  • Increase the population of the animal which may feed on this
  • Decrease the population of competeing organisms for food, sunlight, shelter, and nutrients
  • All of these will have further implications (knock-on effect) for other components of the ecosystem as well, some positive, some negative.

2) Agriculture and Farming

  • Fertilizers are used to increase crop yield and then are terminated
  • These may harm animals that feed on the crops
  • Fertilizers in the soil get leeched to rivers by rain, causing water pollution
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Temperate Deciduous Forest

Global distribution: Located outside of the tropics, in Europe, USA, Japan, Australia and NZ.

Climate: Temperate Meritime climate, tempratures from -30 to 30dC, precipitation is distributed evenly throughout the year

Soil: Rich, fertile brown soil that supports much plant life

Vegetation: Moderately dense canopy, or tree layer (elm, oak) shrub layer (holly) plants (grass, bracken) and fungi. Plants loose their leaves in the winter.
Flora consists of 3-4 tree species per square km
Fauna consists of squirrels, rabbits, deer, fox, birds

Adaptations: Thick bark to protect trees from the cold in winter
Broad, thin leaves to capture as much sunlight as possible
Leaves are dropped in winter to minimize water loss
Plants grow on the forest floor in spring when they can get sunlight before the trees grow wide leaves

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Tropical Rainforest

Global Distribution: Found on the equator, central and south America, central Africa and south Asia.

Climate: Equatorial climate, area of low pressure, constant high tempratueres (25-30dC) and heavy daily rainfall, up to 80% humidity.

Soil: Nutrient poor and acidic. Decomposition occurs rapidly and heavy leeching.

Vegetation: Emergents (50m), dense canopy (25-35m), undercanopy, shrub layer.
Flora is highly diverse, 100 species of tree per square km.
Fauna includes bats, birds, small mammals (monkeys) and insects.

Adaptations: Tall trees have Buttress roots for stability
Leaves have a waxy coat and drip tips to prevent water from causing rotting
Trees grow very tall to reach sun and have broad leaves to catch sunlight
Lianas and Strangler Figs use other trees to grow on
Many epiphytes collect rainwater in a central resivour and do not need roots

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Global distribution: Found on the tropics, North America, North Africa, Australia, South Asia.

Climate: Area of high pressure, 30-50dC during the day, below freezing at night, little rainfall concentrated in short bursts (200mm a year) low humidity.

Soil: Rich in nutrients (nitrogen) due to lack of leeching, no humus layer

Vegetation: little vegetation, plants don't grow high or they would freeze at night
Flora includes Saguaro Cactus, Ocatillo Bush, Creosote Bush
Fauna is mainly nocturnal small animals such as reptiles and insects.

Adaptations: Saguaro cactus has long roots to reach the water table, thick stem to store as much water as possible, spikes instead of leaves to prevent water loss via transpiration, grow 10cm a year.
Creosote bush has varnished leaves and a foul smell to put off predators
Ocotillo bush blooms during rainfall then drops its leaves and hibernates.

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