Paper 3 Section A - People and the biosphere

Define biome

A biome is a large-scale global ecosystem characterised by specific environmental conditions, vegetation and animal life

Define ecosystem

An ecosystem is the interaction of a community of living organisms (biotic) with the non-living (abiotic) parts of the environment

Define climate

Climate is the long term pattern of weather conditions in a specific area

What is the global distribution and characteristics of biomes influenced by?

Climate:

• Temperature

• Precipitation

• Sunlight hours

Describe the pattern of the distribution of biomes around the globe and explain why there is this pattern

Biomes usually occur in latitudinal belts (the specific biomes across the globe are usually present at similar latitudes)

• This is because the climate in these regions is similar due to atmospheric circulation (temperature, precipitation)

However there are some variations to this!

Why is there variation in the pattern of the global distribution of biomes occurring in latitudinal belts?

Local factors can alter the biome distribution locally

• Local factors influence environmental conditions

Explain the global distribution, climate and characteristics of the tropical forest biome

• Global distribution:

  • Along the equator (0°)

  • South America

• Climate:

  • Climate is the same all year round, no definite seasons

  • Warm, moist climate, around 26°

  • Extremely high precipitation (2000mm a year)

  • 12 sunshine hours

• Characteristics:

  • Dense forest with very tall evergreen trees

  • Layered vegetation

  • Very high biodiversity

  • Nutrient poor soil:

    • Very fast nutrient cycling, so nutrients are not stored in the ground; plants grow rapidly and shed leaves all year round (due to high temperatures, large amounts of sunlight and high precipitation) due to high temperatures there are high rates of decomposition, allow the shallow-rooted plants to reabsorb nutrients immediately, leaving little to stay in the soil

    • Heavy rainfall causes rapid leeching

Explain the global distribution and characteristics of the temperate forest biome

(UK’s biome)

• Global distribution:

  • Around 40-60° N and S of the equator

  • Eastern USA, UK

• Climate:

  • Have four distinct seasons; warm summers cold winters

  • Mild temperature

  • Moderate precipitation year round

  • Days are shorter in winter and longer in summer

• Characteristics:

  • Deciduous trees (lose their leaves in winter/ autumn to reduce water loss by transpiration — frozen ground makes it harder to absorb water)

    • Seasonal climate: colder winters

  • Moderate biodiversity

    • Moderate precipitation

  • Nutrient rich soils

    • Four distinct seasons: as deciduous trees shed their leaves, they decompose to create a thick, nutrient-rich layer

What are:

• Deciduous trees?

• Coniferous trees?

• Deciduous: trees that lose their leaves annually

• Coniferous: evergreen trees with needle-shaped leaves

Explain the global distribution and characteristics of the boreal forest biome

(Also known as the taiga forest)

• Global distribution:

  • 50-70° N and S

  • Russia, Scandinavia

• Climate:

  • Short summers and long winters

  • Very cold winters and mild summers

  • Low precipitation

  • Lots of sunlight hours in summer months, but little or none in winter

• Characteristics:

  • Coniferous trees (remain evergreen, needle-shaped leaves)

    • Retain green leaves all year to maximise photosynthesis, reduce water loss and allow snow to fall off easily

  • Low biodiversity

    • Cold temperatures and long winters make it hard for all species to survive

  • Thin, nutrient poor acidic soils

    • Cold temperature so slower rates of decomposition, so fewer nutrients are released into the soil

Explain the global distribution and characteristics of the tropical grassland biome

(Also known as the savannah)

• Global distribution:

  • 15-30° N and S

  • Eg. Kenya

• Climate:

  • Precipitation is very seasonal, but overall yearly precipitation is low

  • Short wet season, long dry season

  • High temperatures year round

  • Many sunlight hours all year round

• Characteristics:

  • Tall grasses with few scattered trees

    • Wet season allows grass to grow quickly, however the long dry season prevents many trees from growing + wildfires

  • Large grazing animals

    • Open grassland provides large areas of food for herbivores

  • Drought resistant plants

    • Plants are adapted to survive long dry periods

  • Thin and not very fertile soil

    • High temperatures cause rapid decomposition of plants, however heavy rain in the wet season causes leeching

    • Rapidly taken up by vegetation

Explain the global distribution and characteristics of the temperate grassland biome

(Also known as prairies)

• Global distribution:

  • 30-40° N and S

  • Eg. central USA

• Climate:

  • Hot summers and cold winters

  • Low precipitation

  • Varying sunlight hours throughout the year

• Characteristics:

  • Grasses dominate, very few trees

    • Rainfall is not high enough for trees to grow

  • Fertile soils

    • High temperatures in the summer cause high rates of decomposition, so soils are nutrient rich

  • Large open landscape

    • Limited rainfall prevent dense vegetation from forming

Explain the global distribution and characteristics of the desert biome

• Global distribution:

  • 30° N and S of the equator

  • Eg. north Africa

• Climate:

  • Very low rainfall

  • Very hot temperatures in the day and very cold at night

  • Many sunlight hours during the day (due to low cloud cover)

• Characteristics:

  • Very sparse vegetation

    • Very low precipitation

  • Plants have very small leaves/ spines

    • To reduce water loss

  • Very low biodiversity

  • Nutrient poor soil

    • Sparse vegetation means that there is little leaf litter to decompose; dry climate means organic matter is slow to decompose

Explain the global distribution and characteristics of the tundra biome

• Global distribution:

  • Far north arctic circle 60°-70° N and S

  • Canada, Northern Russia, Norway (sunlight hours)

• Climate:

  • Two main seasons: long very cold winter, short cool summer (layer of soil thaws and plants grow rapidly)

  • Overall very low temperatures

  • Low precipitation

  • Near-continuous daylight in the summer and little during winter

• Characteristics:

  • Permafrost

    • Due to very cold temperatures; limits root growth so reduces biodiversity

  • Low-growing vegetation (shrubs, grasses, mosses)

    • Roots cannot grow deep in the soil (permafrost)

  • Nutrient poor soil due to cold, dry climate,

    • Organic matter decomposes slowly

Explain how and why the climates of different biomes varies

• Sunlight hours

  • Depends on proximity to equator

  • Depends on precipitation levels (atmospheric circulation cells - 0° and 60°), and thus cloud cover

• Temperature

  • Proximity to equator

• Precipitation

  • Atmospheric circulation cells

Describe the influence of climate on biomes

• Precipitation

  • High precipitation allows forests, low only allows grasses and deserts

  • Can cause leaching, reducing nutrients in soil

• Temperature

  • Increases photosynthesis and thus plant growth — more vegetation and biodiversity

  • Increases rates of decomposition: nutrients in soil

• Sunlight hours

  • Less sunlight hours reduce plant growth and shorten growing season

Explain the local factors that can limit biome distribution locally (4)

• Altitude

  • At higher altitudes it is colder, so fewer plants grow there which also limits the number of animal species

  • Precipitation increases with altitude

• Rock type

  • Some rocks are easily weathered, which releases nutrients and chemicals into soil - nutrient rich soil

  • Different rock types contain different nutrients and chemicals

  • Permeability of rocks affects how wet or dry the surface of the land is, which affects the distribution of organisms as they need to be by water sources to survive; some plants prefer wet soil, some prefer dry

• Soil type

  • Soils can be neutral, acidic or alkaline which affects the types of plants that can grow there

• Drainage (+ water availability): drainage is how fast water enters and leaves the soil

  • Some plants prefer wet soil, others dry soil

  • If soil becomes waterlogged, marshes can form where there is very little vegetation

Define biotic and abiotic

• Biotic: the living parts of the ecosystem (eg. fauna (animals) and flora (plants))

• Abiotic: the non-living parts of an ecosystem (eg. soil, water, rock atmosphere)

Give examples of how biotic and abiotic components of biomes interact

Define the biosphere

The biosphere is the layer of the Earth occupied by living organisms, between the atmosphere and the lithosphere where all plants, animals etc. are found

Name some of the resources that the biosphere provides for indigenous and other local people

• Food

  • Fruits, vegetables, hunting, catching fish

• Medicine

  • Lots of plants have medicinal properties

• Building materials

  • Wood

• Fuel

  • Wood, dried grass, dried animal dung

What is the biosphere increasingly exploited commercially for?

• Energy

  • Large areas of land are deforested to make space to grow crops to use as biofuels, or for coal mines or for power stations

  • Drilling for oil and gas in the tundra is damaging the biosphere

    • Oil spills

    • Pipelines can act as obstacles and disrupt animals’ movements to feeding and nesting grounds

    • Heat from pipelines melt permafrost; this is bad as as permafrost thaws it decomposes, releasing greenhouse gases (permafrost acts as a massive carbon sink)

• Water

  • Aquifers (groundwater stores) are being depleted

  • Lakes and rivers are being depleted, destroying habitats for many

• Mineral resources

  • Eg. gold, iron, metals are being depleted at a much faster rate than their formation (for consumer goods, construction, electrical appliances)

  • Mines are responsible for large amounts of deforestation

  • Toxic chemicals from mining are washed into streams and rivers, killing wildlife

State the globally important services the biosphere provides, acting as a vital life support system (4 categories)

• Provisioning services (goods)

  • Locally: food, medicine, fuelwood, building wood

  • Global: timber construction, wood for paper, biofuels, aloe vera cosmetics

• Supporting services

  • Photosynthesis

  • Nutrient cycling

    • Biomass is broken down, releasing nutrients back into soil for future plant growth

  • Soil formation

    • Weathering processes of rock, releasing minerals to form soil

• Regulating services

  • Hydrological cycle

    • Trees purify and regulate (interception, infiltration, storage, transpiration) the flow of water throughout the cycle

  • Regulation of composition of atmospheric gases

    • Forests release oxygen

  • Carbon cycle

    • Forests are carbon sinks

• Cultural services

  • Education

  • Tourism

  • Science

  • Well-being

State the three main globally important services that the biosphere provides

• Regulation of composition of gases in the atmosphere

  • Respiration

  • Photosynt

  • Carbon sequestration/ storage

• Soil health

  • Decomposers

  • Interception

  • Roots

  • Movement of earthworms and plant roots

• Regulation of hydrological cycle

  • Infiltration

  • Transpiration

  • Interception

  • Animals storing water in bodies

Describe how the biosphere regulates the composition of the atmosphere

• Photosynthesis

  • Plants absorb carbon dioxide from the atmosphere and releases oxygen

• Respiration

  • Organisms respire by absorbing oxygen from the atmosphere and releasing carbon dioxide

• Carbon sequestration/ storage (capturing and storing atmospheric carbon)

  • Plants store carbon in biomass

  • Dead plants and animals become fossil fuels, storing carbon; or their dead biomass ends up in the soil creating a carbon sink

Describe how the biosphere maintains soil health

• Decomposers break down dead biomass, releasing nutrients into the soil

• Plants absorb nutrients from the soil; when they die or shed their leaves, the nutrients return to the soil, creating a continuous nutrient cycle

• Vegetation intercepts rainfall before it reaches the ground, preventing leaching

• The roots of vegetation hold soil together and maintain soil structure, allowing plants to grow

• Animals (eg. earthworms) spread nutrients throughout the soil, allowing them to reach plants and therefore allowing them to grow

Describe how the biosphere regulates the flow of water within the hydrological cycle

• Interception

  • Less surface run off, prevents flooding and soil erosion, allowing soil to retain water; crucial for maintaining soil moisture levels

• Transpiration

  • Releases water vapour into the atmosphere

• Living organisms store water in their bodies

• Infiltration

  • Plant roots create pathways in soil, increasing infiltration; increases groundwater supplies, reduces surface runoff

Explain why there is increase demand for food, energy and water resources

• Population growth

  • More people require more resources

• Rising affluence

  • Wealthier people have more disposable income, which increases resource consumption

  • People can afford higher level technology and cars which require large amounts of energy to manufacture and run

  • Afford showers and toilets, increases water use

• Urbanisation

  • Cities require more resources for construction

  • Requires more energy to transport food and water long distances from rural areas to meet the increased demand in cities

  • Requires energy for street lights, traffic lights

• Industrialisation

  • Increasing numbers of factories, which require energy to run

  • Manufacturing goods requires large amounts of resources and energy

Describe the optimistic theory on the relationship between population and resources

Boserup theory

• No matter how large the population grows, we will always discover more ways to sustain food and resource supplies

• If resource supplies become limited, people will come up with new ways (eg. through technological advances, new agricultural technologies) to avoid hardship

Describe the pessimistic theory on the relationship between population and resources

Malthusian theory

• Theorised that population increases exponentially, but resources only increase linearly, meaning that the population will eventually run out of food and resources

• He believed that when this happened, people would be killed by catastrophes such as famine, illness and war until the population returns to a level that could be supported by the resources available