Biological resources

Agroecosystem

The community of living organisms, the abiotic environment and the interactions between them in an agricultural area of land and cover around half of all habitable land on earth

Subsistence agriculture

A crop which is grown to feed the family or local community

The main inputs of agroecosystems

Technology available to cultivate, the abiotic environment determining which soecies are suitable to grow, human inputs such as heat/fertiliser/light

Environmental factors influencing selection of species

Light intensity and day length, water availability, temperature, soil fertility, relief, pest problems, topography

Cash crops

A crop which is grown to sell for a profit

Heterotroph

An organism that needs to eat other organisms for nutrients

Autotroph

An organism which can produce its own nutrients such as plants using photosynthesis

Examples of pest species

Livestock predators, crop and livestock pathogens, herbivores that eat crops, crop/livestock competitors

Wind velocity and direction may impact…

Seed dispersal, soil erosion, crop damage

define topography

The shape of the lands physical features

Define relief

The measure of the variation in elevation including height and slopes across a landscape

Social factors of farming

Human related factors that can include market demand for a certain product considering consumer choice

Political/economic factors

Factors such as how the price of product will sell on the market and government grants/subsidies for sustainable farming

free range farming methods

Where organisms are kept in as close to natural conditions as possible

Organic products

Are cultivated using all natural processes with no artificial chemicals such as fertilisers or pesticides

Productivity equation

Yield/unit area

Yield equation

The volume, weight, or mass of a food product

Abiotic conditions in agroecosystems

Topography, temperature, light, water, wind

Why do farmers control temperature (importance) (abiotic factors for agriculture)

enzyme’s can be denatured if temp moves outside of an organisms range of tolerance

if temps are too cold enzymes won’t be working quickly = slow growth,

keeping crops and livestock warm prevents frost formation and they waste less energy keeping warm and instead the energy goes into growth

How do farmers control temperature (abiotic factors for agriculture)

topography of the land eg farmers may choose fields rather than valleys because of the dense cold air that collects there,

south facing slopes in the northern hemisphere receive greater amounts of sunlight and are warmer,

greenhouses can be used to maintain temps because of the transparent material that allows light penetration

Farmers can place a transparent woven cloth over fields to act as an insulator which traps a layer of warm air close to the soil keeping seedlings warmer

Keeping livestock inside thermostatically controlled buildings so they are at optimum temp

Evaluating farmers control of temperature (abiotic factors for agriculture)

higher temps will lead to higher evapotranspiration rates meaning crops will require more water from irrigation leading to depletion of water sources

Energy used to heat barns and keep livestock warm most often comes from combustion of fossil fuels which releases greenhouse gases into the atmosphere

Building farm buildings/greenhouses have a high embodied energy meaning they require a lot of energy to construct and maintain

Why do farmers control light intensity (importance) (abiotic factors for agriculture)

Intensity of light affects rate of photosynthesis, brighter light producing more rapid photosynthesis.

Day lengths affects growth and crop development, oats for example require longer day lengths and more light while maize requires less,

Day length can also affect the reproductive function of some livestock species eg long day length increases milk production, egg production is greatest when days are long

How do farmers control light intensity (abiotic factors for agriculture)

Greenhouses made from transparent materials allow light penetration and increase photosynthesis rate

crops and livestock can be grown inside barns with artificial lighting that can control intensity and day length and mimic different seasonal lighting which can increase the amount of mating seasons

Choosing a field that is south facing in northern hemisphere and vice versa receives more day light

Evaluation of farmers control of light intensity

Energy required to power artificial lighting most likely released from combustion of fossil fuels which releases greenhouse gases

Building greenhouses/barns have a high embodied energy in extracting the materials construction and maintenance

Why farmers control water availability (importance) (abiotic factors for agriculture)

Water is a universal solvent meaning it is excellent at dissolving minerals, plants absorb nutrients such as nitrates through the roots only if they are dissolved in water.

Plant cells are filled with water to make them turgid allowing the structure of young stems to be strong so they don’t wilt

If plants are dehydrated they’ll stop taking in gases such as c02 meaning photosynthesis slows down decreasing growth and yield rate

Drainage of soils is very important in preventing water logging which leads to anaerobic conditions where denitrification occurs removing nitrates from the soil and reducing fertility, but rapid drainage can cause excessive leaching of nutrients which can then pollute nearby bodies

How farmers control water availability (abiotic factors for agriculture)

Irrigation of the soil involves applying large volumes of water, drainage ditches or pipes built into the soil to allow water to drain away and prevent water logging of the soil

Ploughing helps to aerate the soil so that it is less likely to become compacted and waterlogged allowing for better drainage, encouraging worm populations as they tunnel through soil also aerates it

Adding mulch materials to the surface of the soil such as wood chipping s reduces evaporation of water from the soil surface

Evaluation of how farmers control water availability (abiotic factors for agriculture)

Irrigation uses huge volumes of water, a large proportion of which is leached from the soil into waterbodies, drip irrigation is a more sustainable alternative

Overploughing can lead to destruction of soil peds which makes eroding more likely

Mulching has other benefits such as preventing growth of weeds, of those that are biodegradable nutrients can be released into the soil by break down

Why do farmers control soil fertility (importance) (abiotic factors for agriculture)

Crops absorb nutrients that are dissolved in water from the soil via their roots, these nutrients such as nitrates and phosphates are used for a range of metabolic processes eg growth and making proteins

How farmers control soil fertility (abiotic factors for agriculture)

Applying organic fertiliser such as manure has low solubility in water so is less likely to leach, manure is decomposed by soil biota to release nutrients slowly into the soil

Applying inorganic fertilisers such as NPK which contain nitrates, phosphorous and potassium. This releases huge volumes of nutrients into the soil at once which are very soluble and often leach into water bodies

Planting legumes which have nitrogen fixing bacteria in their root nodules reduces the need to apply nitrogen fertilisers to the soil

Keeping soil aerated ensures there is a large population of aerobic nitrifying bacteria which releases nitrates and increases soil fertility

Adding mycorrhizal fungi to the soil which forms a symbiotic relationship with crop roots, the fungi are very efficient at absorbing phosphates from sugar made in photosynthesis

Evaluation of how farmers control soil fertility

Leaching of nutrients in water bodies can cause cultural eutrophication which deoxygenates the wster body, leading to the death of aerobic species

Inorganic fertilisers are made during the haber process and which uses the combustion of fossil fuels to produce the high temps required releasing greenhouse gases into the atmosphere

Hydroponic systems are an intensive agriculture method where a large number of inputs are required, usually indoors using energy intensive systems to power artificial lighting and pumps for the nutrient solution, having no soil means no pathogens or weeds that could reduce yield

Why do farmers control aeration (importance) (abiotic factors for agriculture)

Aerated soils have higher rates of aerobic decomposition nitrification both of which increases soil fertility.

Aerated soils have larger populations of worms which burrow through the soil increasing drainage and reducing chance of water logging.

Aerated soils are easier for roots to penetrate through pore spaces in the soil allowing the plant to absorb water and nutrients

How do farmers control soil aeration (abiotic factors for agriculture)

Ploughing turns over the soil to aerate the surface layers

Adding organic matter provides food for soil organisms such as worms which burrow through the soil creating tunnels aerating it

Having low livestock density will prevent compaction of the soil which would lead to anaerobic conditions

Reducing use of heavy machinery would prevent compaction

Control of other abiotic factors

Soil salinity- leads to osmotic dehydration, controlled by testing irrigation water to ensure small concentration of salt, desalination is an energy intensive process

Soil pH- high pH reduces nutrient solubility, low pH increases nutrient solubility = more likely to leach, controlled by monitoring pH, methods such as crushed lime must be extracted from the lithosphere

Wind velocity- high winds increase soil erosion and increase evapotranspiration meaning more water needed to replace it, controlled by planting hedgerows 1m height = 40m protection, tree growth takes a long time before trees are big enough to protect organisms

Topography- steep topography not suitable for growing crops as it increases soil erosion, controlled by contour ploughing or terracing to reduce sooo gradient and rain splash erosion, ploughing uses fossil fuels

What is farm diversification

Finding other ways to make money using the farm eg. Tractor rides

Limiting factor

The factor in shortest supply and is therefore limiting the rate of a named process eg photosynthesis

Embodied energy

Total energy consumed in material production and construction

The haber process

A method to produce inorganic fertiliser that releases greenhouse gases into the atmosphere

Pests

Any organism that negatively impacts a farmed species eg predator of livestock, competitor of crops, pathogens of crops, parasites, herbivores eating crops

2 main categories of pest control

Chemical pesticides and cultural pest control

Endemic pests

Usually present in an area but in smaller numbers

Epidemic pests

Not normally present in an area but may appear in large rapid outbreaks

Cultural pest control

Methods to control pests that do not involve chemical pesticides

Cultural pest control methods

These are non pesticides methods where crops or livestock are cultivated to reduce risk of pest damage:

Crop rotation,

planting companion crops,

creating predator habitats to encourage colonisation by predators of common pest species

Sterile male technique where because females only mate once in a lot of insects, sterilised males’ sperm cant fertilise eggs during mating leading to population decline

Pharamone traps that release an artificial scent which attract a species, once trapped they can be relocated or killed, can also be used as a sampling technique, work best in enclosed area because higher concentrations of the pheromone

Endemic vs epidemic pests

Endemic are always present in small to moderate numbers, epidemic pests are not normally present but there are outbreaks where they rapidly become major problem

Indigenous vs introduced pests

Indigenous are native to the area, introduced come from other areas and are less likely to have natural predators

Crop rotation (biotic factors for agriculture)

Involves a farmer changing the crop species grown in a field every year/season so pest species can’t increase in population as their food source will be frequently removed so they’ll die out before that crop is grown again

Disadvantage- only will work on soecies specific pests that only eat one type of crop

Planting companion crops (biotic factors for agriculture)

These are other crop species that are planted alongside the harvestable crop to increase its yield eg. Planting onions that smell strongly acting as a barrier to the harvestable crop and hide them from pests, sacrificial crops are planted for pests to eat instead of the harvestable crop

Disadvantage- uses space in the field meaning fewer harvestable crops can be planted reducing yield and profit gain, also increase competition for soil nutrients, water availability and sunlight with the harvestable crops if planted close by

Biological control

When a non native predator/pathogen is introduced to reduce pest size when a non native pest species is in an area with no natural predators, yet they should be specialist feeders as to not eat other things eg. Cane toads introduced into America to control beetle pests but have ended up eating other species and have colonised a huge area

Selective breeding

Where two individuals are bred together due to desirable characteristics eg. Higher resistance to pests, increases the probability that their offspring will inherit this as well, disadvantage is that they can inherit less favourable traits as well

Genetic engineering/modification/ transgenics

Transferring genes from one species into another which code for a trait, these genes tend to come from wild crop relatives but can only introduce characteristics that exist within those gene species eg. Golden rice had a a gene for vitamin A transferred to reduce chance of blindness in low income countries

Advantages- can increase pathogen resistance, desirable characteristics can be introduced without undesirable ones

Disadvantages- transfer through the food chain where GM crops approved for animal feed have been detected in low levels at human consumption

Optimum density

Ideal population density for maximum growth

Intraspecific competition

Competition among individuals of the same species

Energy subsidies

energy intensive processes like fertilisers and irrigation

Chemical pesticides

Organochlorines- group known for environmental persistence

Organophosphates-disrupt the nervous system function in pests

Pyrethroids- synthetic pesticides modelled after natural pyrethrums

Neonicotinoids- affect insect nervous systems

When chemical pesticides are species specific they kill fewer non target species, others can be water soluble and leach into water bodies

For livestock- antibiotics administered to treat existing bacterial infections and prevent infection of high stocking densities

Hormonal pesticides- target biological processes and cause natural processes to happen earlier/later causing harm to pests

High stocking density

Large number of animals in a confined space

Contact pesticides

Sprayed over the crops and sit on plant surface

Systemic pesticides

Added to the soil to be absorbed by plant roots into the tissue, are more likely to leach and runoff and because they’re mobile kill more non target species

Inbreeding

Breeding of two closely related individuals which can lead to increased chance of offspring inheriting genetic diseases, stud books can be used to record genetic relationships of individual animals to ensure close relatives arent breeders together

Outbreeding

Opposite to inbreeding where farmers will only breed individuals not genetically related reducing risk

Crossbreeding

Where farmers take two breeds of the same species and interbreed them carried out when each breed has desirable characteristics so the offspring will have a combo of the two

Sexual reproduction

Offspring that combines the genes of two parents

Controlling the number of individuals kept in an area is called?

Livestock- stocking density

Crops- planting density

Monocultures

Involve cultivating a single species makes cultivation easier due to same water requirement for eg but pests and diseases can spread rapidly

Poly culture

Cultivation of multiple species together

Asexual reproduction of plants

Vegetative propagation- new plant grows from part of parent plant eg strawberry runners

Micropropagation- type of vegetative propagation that happens in a lab where small tissue sample from parent plant is grown in agar gel and nutrients to form genetically identical new plant is grown

Why would farmers want to clone their plants

Genetic uniformity means they can guarantee the crops characteristics such as plants with high salt tolerance leading to a whole population like that so saltwater incursion is less of a risk

Asexual reproduction of animals

Nuclear transfer- nucleus of an organism we want to clone is transferred into an egg cell of a donor with all the genetic info, it’s planted into a surrogate mother where it divides to form a new identical organism

Energy subsidies and examples

Any input into the agriculture system that requires energy to do so

Examples:

Manufacture of fertilisers/pesticides such as the haber process which requires high temps and pressure from combustion of fossil fuels

Machinery used to spray agro chemicals, plough fields or pull trailers, tractors will most likely run on fossil fuels

Heat generated by electricity for drying grain in barns or keeping livestock warm

Intensive farming

Farms that produce high yields using high inputs on a small land area

Extensive

Farms that produce lower yields using lower inputs over a larger land area

Productivity vs efficiency

Productivity- amount of yield per unit area of land

Efficiency- amount of yield per unit energy input

Examples of energy subsidies and their extensive agriculture alternative

Manufacture of fertilisers/pesticides- organic fertilisers such as manure and cultural pest control such as predator habitats

Machinery used to spray, plough and pull trailers- tractors running off electricity that has been produced by renewable energy resources

Heat generated for electricity in barns for drying grain or keeping livestock warm- livestock heated by renewables such as geothermal energy heat pump

What is energy ratio

A measure of the efficiency of a farming system comparing the number of energy inputs to outputs, systems with high energy ratios are producing large amount of yield per unit input of energy which is efficient

Equation: Energy output/energy inputs

What is food conversion ratio?

The mass of food required to produce a specific increase in biomass of livestock, a lower ratio tells us that a lot of the food eaten goes into growth, a high ratio tells us energy is lost as heat (animals keeping warm) or respiration

Energy transfer in food chains

Energy is transferred from producers to consumers with losses occurring at each trohpic level

Habitat impacts of agriculture

Habitat destruction takes place to make space for agriculture eg. Deforesting woodland to create space for crops, or draining wetland areas meaning aquatic or semi aquatic species won’t be able to survive there

Intensive farming methods using ploughs and machinery will erode and degrade the soil = lower soil quality = death of native species

Diversity is reduced by planting mono cultures and the removal of native predators/herbivores through culling or pesticides

Diversity can increase if soecies colonise areas in agroecosystems such as hedgerows, hay meadows or grazed moorlands

Invasive species can be introduced if they’re being cultivated or used as biological control agents, they can outcompete native species

Pollution in agriculture

If a pesticide is lipid soluble it can cross cell membranes and bioaccumulate inside living organisms and biomagnify uo the food chain. If it’s water soluble it will be able to dissolve in rainwater and leach into water bodies.

Only inorganic fertilisers cause eutrophication as they are the input of large quantities of nutrients into a water body. The concentration of nutrients can also lead to weed species having access to more nutrients and outcompete other plants

Machinery used eg. Tractors often run off fossil fuels such as diesel or petrol which when combusted release c02 and carbon monoxide into the atmosphere, livestock release methane from digestion, certain crops such as rice need to grow in anaerobic waterlogged soils releasing methane

Agriculture impacts on the hydrological cycle

Irrigation of crops means large volumes of water are removed from stores like aquifers or reservoirs which can cause them to be depleted, or irrigation can cause waterlogged soil reducing infiltration rate of surface water from precipitation

Long term crops such as trees have a more constant evapotranspiration rate whereas harvestable crops like vegetables will reduce the rate when removed

Agroenvironmental schemes

Schemes placed by the government such as the environmental stewardship scheme that encourage farmers to implement sustainable practices by including methods like planting hedgerows or wildflower meadows to encourage diversity to provide habitats. Farmers can then be awarded grants and subsidies for implementing these practices. ELMS is another example where the government pays farmers for environmental benefits including water quality and carbon storage

Biomagnification

Increase in substance concentration uo the food chain

Eutrophication

Nutrient overload causing algal blooms in water