Y1SY - Earth Systems Science - Biosphere

Key controlling extrinsic factors on biomes

• Temperature

• Moisture availability

• “Zonal factors” ( Things that change gradually – like climate, seasons)

• “Azonal factors (Sudden events in time and space)

• Net Primary Productivity = Tonnes of biomass produced per year

Tropical Rainforest: Key features

• % Land Surface: 11%

• Rainfall: 2000–4000 mm/yr

• Climate Factors:

  • Average temperature of coldest month > 17°C

  • Little seasonality

• Net Primary Productivity (NPP): 20–25 t/ha/yr

Taiga (Boreal Forest: Key features

• % Land Surface: 8%

• Rainfall: 350–1000 mm/yr

• Climate Factors:

  • Medium-length growing season

  • Snow common

• NPP: 2.5–5 t/ha/yr

• Other Comments:

  • Coniferous forests

  • Low species richness

  • Dominant species: spruce and pines

Tropical Grasslands (savannah): Key features

• % Land Surface: 10%

• Rainfall: <1200 mm/yr

• Climate Factors:

  • Seasonal drought

• NPP: 10–20 t/ha/yr

• Other Comments:

  • Fertile soils

  • Large mammals

  • Vegetation maintained by grazing and fire

Chaparral (Mediterranean): key features

• % Land Surface: 3%

• Rainfall: 250–750 mm/yr

• Climate Factors:

  • Summer drought

  • Wet winters

• NPP: 0–15 t/ha/yr

• Other Comments:

  • Evergreen thickets

  • Small oaks or eucalyptus

  • Many species are fire-dependent

Temperate Deciduous Forest: Key features

• % Land Surface: 4.5%

• Rainfall: 759–2000 mm/yr

• Climate Factors:

  • Long growing season

  • Temperatures rarely < –12°C

• NPP: 5–20 t/ha/yr

• Other Comments:

  • Broad-leaved trees (oak, maple, beech)

  • Many areas cleared for agriculture

Deserts: Key features

Deserts

• % Land Surface: 25% (largest biome in table)

• Rainfall: <250 mm/yr

• Climate Factors:

  • High temperature fluctuations

  • Low, infrequent rainfall

• NPP: 0–2.5 t/ha/yr

• Other Comments:

  • Sparse flora

  • Xerophytic plants (succulents)

  • Highly adapted fauna

Tundra - Key features

• % Land Surface: 5%

• Rainfall: <250 mm/yr

• Climate Factors:

  • Long winters

  • Short growing season

• NPP: 0–2.5 t/ha/yr

• Other Comments:

  • Mostly treeless

  • Mosses, lichens, dwarf shrubs

Temperate Grasslands: Key features

Local factors influencing the distribution of species/ individuals

• Local temperature or variations in temperature (shelter, altitude, aspect)

• Local moisture (inc. humidity, current flow)

• Soil structure and substratum

• pH of soil and water

• Nutrients & salinity

Shelford’s law tolerance (1913)

For an organism to succeed in a given environment, each of the conditions must remain within the tolerance range of that organism

if any condition exceeds the maximum or minimum tolerance of that organism, the organism will fail to thrive and be eliminated”.

lower incipient lethal level

the lowest environmental parameter, like temperature or concentration of a substance, at which organisms can survive or start to experience lethal effects

upper incipient lethal level

the highest environmental parameter, like temperature or concentration of a substance, at which organisms begin to experience lethal effects.

4 main parts of soil

·       Air, water, organic matter & mineral particles.

Anderson Ranch Reservoir, Idaho - key facts about the slopes

o   South-facing slopes: warmer, sunnier, more evaporation, less snow

§  Vegetation: grasses, low shrubs, forbs

o   North-facing slopes: cool, shady, less evaporation, deeper snowpack.

§  Vegetation: large coniferous trees (Douglas Fir, Ponderosa Pine)

Factors affecting soil formation

•        Climate - for every 10 ºC rise in temp., the speed of chemical reactions increases by 2-3 times; biological activity rates double, evaporation increases (limit: to about 30 ºC).

•        Parent material (rock type)

•        Topography (altitude, slope, aspect)

•        Organisms inc. vegetation

•        Time: 30 cm layer of soil takes 1000 – 10,000 years to form

What does ‘niche’ mean in terms of biosphere?

Places where plants and animals can exist

Two types of niche

•        Fundamental niche

–      Contains ideal conditions for the species requirements (zone of tolerance)

–      Is only realized in simple situations, with no other competitors

•        Realised niche

–      The actual area occupied following biotic and other interactions

Autotropes

Primary producers

Hetrotropes

Secondary and tertiary consumers

What is an ecosystem?

Comprises organisms, biotic(living) factors and their environment, abiotic (non-living) factors.

What shapes an ecosystem?

The interaction between biotic and abiotic factors

2 Main reasons as to why organisms live where they live

Dispersion and migration

4 types of interactions between organisms

Competition: Interaction is detrimental to both special

Predation: Interaction is beneficial to one species and detrimental to the other

Mutualism: Interaction is beneficial to both species

Mutualism: Interaction is beneficial to both species

Examples of each of the 4 types of interactions

-Competition: Interaction is detrimental to both special

Example: Lions and hyenas in the African savanna both hunt similar prey (like zebras or antelopes). Their competition reduces food availability for both groups, and conflicts can lead to injury or wasted energy.

 

-Predation: Interaction is beneficial to one species and detrimental to the other

Example: A hawk hunting and eating a mouse. The hawk gains food and energy, while the mouse loses its life.

 

-Mutualism: Interaction is beneficial to both species

Example: Bees and flowering plants. Bees collect nectar (food) from flowers, while flowers benefit from pollination, which helps them reproduce.

 

-Commensalism: One species benefits from the interaction but the other is unaffected

Example: Barnacles attaching to whales. Barnacles gain mobility and access to nutrient-rich waters, while whales are generally unaffected by their presence.

What are the two survival strategies

K-strategies and R-strategies

R-Strategies = key features

o   Organisms with a high intrinsic rate of population increase (r)

o   Colonise temporary habitats

o   Opportunistic

o   Live in unpredictable and rapidly fluctuating environments

o   Migration is important

o   Often rapid population growth followed by sudden and large decline

o   Examples: locust, dandelion, bacteria

K-Strategies = key features

o   Organisms limited in number by the environment’s carrying capacity (K)

o   Live in stable, predictable habitats

o   Slow growing

o   Intensely competitive

o   Often large in size

o   Invest time & energy in rearing offspring (resources)

o   Examples: oak tree, elephant, whale, human

What is ecological succession?

: the non-seasonal, directional and continuous pattern of colonisation and extinction on a site by species populations

-

What does ecological succession usually lead to (2 ways)?

usually leads to increased complexity of community structure and increased biodiversity

-and usually communities go from r-dominated to K-dominated species (r & K growth strategies)

2 types of ecological sucessions

·       Primary – starts from bare ground (e.g. Rakata after 1883 Krakatoa eruption)

o   E,g sand dunes

·       Secondary – takes place after a disturbance to an existing ecosystem (often allogenic)

Allogenic vs Autogenic

o   Allogenic - occurring as a result of changing geophysical forces (external forces); o   Autogenic - resulting from biological processes that modify conditions & resources (internal to ecosystem)