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G1B The Living World Cheat Sheet (DRAFT) by

1.2.1 Ecosystems 1.2.2 Tropical Rainforests 1.2.3 Hot Deserts

This is a draft cheat sheet. It is a work in progress and is not finished yet.

1.2.1 Ecosystems - Feature of Ecosystems

ecosystem
- a unit that includes all biotic components (e.g. plants & animals) and abiotic components (e.g. soil & climate in an area)
· the organisms in ecosystems can be classed as producers, consumers, or decomp­osers
· producer
· consumer
· decomposer
- an organism that uses sunlight energy to produce food
- an organism that gets its energy by eating other organisms - producers or other consumers
- an organism that gets its energy by breaking down material, e.g. dead producers (e.g. fallen leaves) & dead consumers
  (e.g. animal remains) ; e.g. bacteria & fungi
When dead material is decomp­osed, nutrients are released into the soil. The nutrients are then taken up from the soil by plants.
The plants may be eaten by consumers. When the plants or consumers die, the nutrients are returned to the soil.
nutrient cycle
- the interd­epe­ndence of biomass, litter, soil
  -> people & ecosystem components are interd­epe­ndent as well
Components of an ecosystem depend on others, e.g. consumers depend on producers for a source of food or habitat.
interd­epe­ndence
- the dependence of two/more components of an ecosystem on one another
->
hot dry summer > reduced plant growth > fewer berries for birds in the winter > number of sparrows & thrushes fall >
fewer birds for sparro­whawks to hunt so numbers fall
->
hedgrow trimmed > fewer habitats for ladybirds, greenfly & spiders, so numbers fall >
sparrows & thrushes have less to eat, so numbers fall > fewer birds for sparro­whawks to hunt so numbers fall
food webs
producers > primary consumers > secondary consumers > tertiary consumers

· as you move up the food web, energy is lost at each stage, which means less consumers can be supported
· each consumer in a food chain 'wastes' / 'uses' nearly all energy taken in
· around 90% of energy at each level is lost through life processes

1.2.1 Ecosystems - UK Local Ecosystem

Epping Forest

· an area of deciduous forest in London (east)
  - all that remains of a larger forest that colonised England at the end of Ice Age
· ponds & bogs have their own unique species, including 20 types of dragonfly
· for 1000 years, Epping Forest has been managed in various ways,
  e.g. royal hunting ground, timber resources, recreation nowadays
Charac­ter­istics of Epping Forest Food Web

· large number of native tree species, e.g. oak, elm, ash & beech
· lower shrub layer of holly & hazel at 5m, overlying grassesm bracken, fern & flowering plants -> 177 species of moss & lichen
  -> great diversity of producer species
· many insect, mammal & bird consumer species -> 9 amphibian & reptile species and 38 bird species
· 700 species of fungi -> important decomp­osers
How is the ecosystem interd­epe­ndent?

· most trees are deciduous -> adaptation to UK climate
  - trees grow broad green leaves in spring -> maximises photos­ynt­hesis in summer
    -> sheds leaves in autumn & conserve energy in winter
· by mid-au­tumn, forest floor covered with thick layers of leaves ; by spring, the litter all disappears (work done by decomp­osers & detriv­ores)
  -> nutrients stored in leaves now converted to humus in soil, ready to support the new season's plant growth
      [produ­ction of fruits & berries -> primary consumers]
· coppicing - cuttine back trees to encourage new growth of wood
Explan­ation of Charac­ter­istics of Epping Forest Nutrient Cycle

· the biomass store is large due to the great height of trees & dense underg­rowth
· the soil store is large due to plenty of humus
· high flow rates between litter, soil & biomass stores reflect the viogorous cycle of new growth that takes place each year
· the forests also loses a lot of nutrients each year, via leaching, during episodes of heavy rainfall

1.2.1 Ecosystems - Distri­bution of Ecosystems

How does climate influence the distri­bution of global ecosys­tems?

· the most important factor affecting the distri­bution of the world's biomes
· major influence over what plants grow and what animals live in the area
· the climate of an area is mainly influenced by its location on planet earth
  - the closer to the equator, the warmer the climate is
  - the further north / south from the equator, the colder the climate is
How does Hadley cells influence the distri­bution of global ecosys­tems?

· the circul­ation of air in Hadley cells influences climate as well
· places located on the equator tend to be wetter as air rises and condenses to form clouds ;
  - tropical rainfo­rests usually found on the equator · places located on the tropics tend to be drier as air sinks there ;
  - deserts usually found on the tropics
How does local factors influence the distri­bution of global ecosys­tems?

· altitude, relief, ocean currents influence the distri­bution of global ecosystems
· the temper­ature drop is aprox. -0.5° for every 100m increase in altitude
· mountains cause relief rainfall on one side of the range & a rain shadow on the other
· colder currents create arid conditions due to less evapor­ation ;
  warmer currents increases evapor­ation and therefore moisture, resulting in the increased chances of rain

1.2.2 Tropical Rainfo­rests - Charac­ter­istics

climate
· the climate is same all year round with no definite seasons
· the temper­ature is generally between 20-28° and only varies by a few degrees over the year
· very high rainfall, around 2000m per year ; usually rains in the afternoon everyday
soil
· the soil isn't very fertile as heavy rain washes nutrients away
· there are only nutrients at surface due to decayed leaf fall, however this layer is very thin due to fast decay
  in warm, moist conditions
plants
· most trees are evergreen to take advantage of the continual growing season
· really tall trees & dense vegetation cover -> very little sunlight reaches the floor
· there are lots of epiphytes - plants that grow on other living plants to reach higher positions in order to absorb more sunlight
  e.g. orchids & ferns
animals
· rainforest ecosystems contain more animal species than any other
· e.g. gorillas, jaguars, anacondas, tree frogs & sloths
people
· many indigenous people have adapted to life in rainfo­rests, making a living by hunting, fishing, gathering nuts & berries
  and growing vegetables in small garden plots

1.2.2 Tropical Rainfo­rests - Defore­station

Causes

population pressure
mineral extraction
energy develo­pment
commercial logging
commercial farming
subsis­tence farming


- as the population in the area increases, trees are cleared to make land for new settle­ments
- minerals (e.g. gold & iron ore) are mined and sold to make money
- building dams to generate hydro-­ele­ctric power floods large area of forest
- trees are felled for profit and road building
- forest is cleared to make space for cattle grazing, palm oil & soya planta­tions
- forest is cleared so farmers can grow food to provide for themselves & families
Enviro­nmental Impacts
· no roots to bind soil -> soil erosion -> landslides & flooding
· no tree canopy to intercept rainfall & no tree roots to absorb water -> more nutrients washed away ->
  reduces soil fertility
· no trees to remove CO2 & burning vegetation releases CO2 -> more CO2 in atmosphere
  ->adds to greenhouse effect -> worsen climate change
Economic Impacts
· logging, farming, mining creates jobs -> income -> boosts local economy
· large amounts of profit made from selling timber, mining and commercial farming
· destroys resources that countries depend on, e.g. timber & reduces attrac­tiv­eness of area to tourists
· may destroy livelihood of locals - animals & plants relied on to make living may be lost
· pollution of water supplies & increasing dry climates -> water shortages
Sustai­nable Management

selective logging



replanting



ecotourism


· only some older trees are felled ; most trees are left standing
· this means the overall structure of forest is kept, so that the forest will be able to regenerate to be used in future
· helicopter logging is used in Sarawak, Malaysia, removing felled trees with helico­pters instead of trucks

· new trees are planted to replace the ones cut down
· same types of tree planted to maintain variety
· there are laws to make logging companies to replant trees

· ecotourism minimises damage to enviro­nment & benefits locals
· income in ecotourism for locals (e.g. guides, providing accomm­odation & transport) -> less employment in logging
· country's economy reliant on ecotourism -> more incentive & raise awareness for conser­vation
· e.g. ecotourism = largest source of income in Costa Rica (21%)

1.2.1 Ecosystems - Global Ecosystems

Tundra
· found at high latitudes (above 60° N) in Northern Europe, Canada and Alaska
· very cold winters ; brief summers ; little rainfall
· hardly any trees - vegeta­tions include mosses, grasses and low shrubs
· permafrost - a layer of perman­ently frozen ground
Boreal Forest
· found between 50 - 60° N ; also known as taiga
· cold & dry winters ; mild & moist summers
· coniferous trees - evergreen, with needles
Temperate Deciduous Forest
· found mainly in mid-la­titudes where there are four distinct seasons
· warm summers ; relatively mild winters ; moderate rainfall all year round
· deciduous trees lose their leaves in winter to cope with the colder weather
Hot desert
· found between 15 - 35° north & south of the equator where there is little rainfall
· very hot during day ; very cold during night
· shrubs & cacti are sparsely distri­buted in the sandy soil
Grassland
· savannah grasslands are found between the tropics
&nbsp - distinct dry & wet seasons ; relatively low rainfall ; most vegetation is grasses with few scattered trees
· temperate grasslands are found at higher latitudes
&nbsp - more variation in temper­ature ; less rainfall ; no trees - just grasses
Tropical Rainforest
· found around the equator between the tropics, where it is hot & wet all year round
· area of lush forest, with dense canopies of vegetation forming distinct layers
Polar
· found around the north and south poles
· very cold, icy and dry ; not much grows at all
· remains dark for several months each year ; very short growing season - two months