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Summary CCEA AS2 biology
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In-depth set of revision notes for CCEA AS-biology Made using CCEA textbook and revision guide produced through good notes. Received a high A AS biology grade with notes.
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rHUMAN IMPACT ON diversity
human
DIVERSITY
impact on
Intensive agricultural practices- methods to maximise productivity and profit
This causes a reduction in biodiversity as a result of habitat loss and change
Increased use of monoculture Polyculture
-reduce biodiversity due to only one crop produced -growing a range of crops at one time or sequentially
-economically beneficial- ground preparation and (year about)
harvesting -provides a wide range of food and habitats
-build up of pests specific to crop being grown -crop rotation- plant different crops in same field
-growing the same crop year after year can lead -conserves soil fertility as each crop
to reduction of particular minerals in soil requires different nutrients and supports diversity
(as plants are harvested minerals are lost) soil -improves soil fertility when nitrogen fixing
becomes depleted of particular ions so necessary crops so less likely to be depleted of minerals
to apply fertiliser -reduces likelihood of pest build up
Leguminous plants have root nodules that contain
Depletion of soil minerals caused by crop nitrogen fixing bacteria that carry out nitrogen fixation
harvesting before decay and decomposition (nitrogen gas -> nitrates- create AA for protein growth)
returning soil minerals
Pest- in agriculture - any organism
that causes at loss in crop yields
Nutrient enrichment of soils exceeding a 5-10% of total yield
-nutrient enrichment of soil to maximise crop yield
(Nitrate is useful for making AA for protein
growth)
-artificial fertiliser (high nitrate) encourage fast Increased use of organic fertiliser (FYM)
growth on a particular crop so that it outcompetes -promote soil fertility and preserve soil crumb structure
and eliminates slow growing species -farmyard manure releases nutrients at a slower rate
-maintain high stocking rates but loss in soil crumb with less mineral loss due to leaching
structure so increased soil erosion -organic fertiliser more difficult to store and spread and
variable nutrient content
Hedgerow conservation and maintenance
-encourage biodiversity when containing range of
species of tree and hedge as provide habitats and food.
-allowing hedgerow trees to grow to maturity at
intervals in the hedge.
Loss of hedgerow
-loss of biodiversity through habitat loss and food -only trimming on a 2-3 year rotation. (shrubs to
for many species so impacts the food chain flower and produce berries, food for birds)
-act as wildlife corridors which facilitate the
movement and dispersal of species -trimming during late winter (January-February) to
-hedgerows are removed to increase land avoid the destruction of bird nests during the spring
availability for agriculture and summer
-hedgerow loss leads to soil erosion as land is more A shape hedge
exposed and reduction of the soil binding role of -maintaining a range of hedge heights and widths by
tree and shrub roots staggering trimming regimes. This maintains a wide
range of habitats. For example, different
bird species have different preferences for hedgerow
heights and width
When establishing a new hedgerow it is important to
protect the hedgerow from grazing. Planting the
hedge bet ween a double fence, protects the young
hedge and forms an effective boundary in the interim.
Plant a mixture of woody species in a new hedge with
associated biodiversity benefits, ie avoid a
monoculture of hawthorn.
, Broad-spectrum pesticides More integrated pest management (IPM)
-killing organisms of species other than intended approaches are now being encouraged, which include the use
target of narrow-spectrum pesticides that only affect the target
pest species.
-kill soil organisms involves in decomposition and soil
structure Strategies such as crop rotation help prevent the build-up of
large pest populations, as the absence of a specific crop for a
-pesticides can elimanate natural predators and can few years may prevent the pest being able to complete its life
cause pest resurgence so it can return in larger cycle.
numbers
-herbicides- (pesticides used to remove weeds/
competitor species) reduces plant diversity and Increased use of pesticides
reduces variety of food available. -maximise crop production by eliminating pests
Pest-species that damages a valuable crop species
-some species are resistant to pesticides and cause causing economic damage above threshold level
bioaccumulation- build-up of concentrations in
tissues of organisms of higher trophic levels. So use
biodegradable
Biological control - reduces the need for any chemical pesticide No chemical damage to environment
by introducing a predator species that target the pest. No bioaccumulation in food chains
Only targets pest species
In time, likely pests would mutate Pest resistance unlikely
and become resistant to chemical Pest resurgence unlikely.
pesticide /insecticide IPM-integrated Saver money on continuous use of pesticid
pest management Needs little additional action
yt
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Biological control agen
NO Of " Pest
f- Natural predator
←
.
"'t "" " "
Pest "" "
Ñ¥
pestana f "
ecosystem
" "" " " " "
predators
numbertnanbetore number aut.addn.to
%edator
Pest isn't eliminated
but pest
No of predators density
.
reduced below threshold
falls dramatically for economic damage .
Time Time
Predator strips (wildlife corridors)
Small areas of rough grass left undisturbed encourages
increase in number of natural predators.
Carabid beetles and ladybirds thrive in wildlife corridors
and feed on crop damaging aphids
Extend wildlife corridors so that species can move
bet ween habitats
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