Manipulation of food species (agroecosystems) Flashcards
name the 4 types of genetic manipulation
- selective breeding
- crossbreeding
- asexual reproduction
- genetic engineering/transgenics
describe selective breeding + example
choosing parents with desirable characteristics together = offspring with more desirable characteristics
i.e. belgian blue = more meat
give 2 advantages of selective breeding
- remove undesirable characteristics
2. enhance desirable characteristics
give 2 disadvantages of selective breeding
- risk of inbreeding (small gene pool)
2. reduce genetic diversity
describe crossbreeding + example
mating parents of 2 different breeds/varieties
i.e. Zebu with Ayrshire cattle = high milk yield + tolerate heat
give 2 advantages of crossbreeding
- lower risk of inbreeding
2. leads to hybrid vigour or heterosis (increased function of hybrid offspring)
give 2 disadvantages of crossbreeding
- could lead to serious genetic issues
2. characteristics sometimes not predictable
describe asexual reproduction in plants
vegetative propagation: new plant produced from sections of plant i.e. stem
describe asexual reproduction in animals
cloning:
1. egg cell nucleus taken out
2. replaced with donor nucleus (fused)
3. embryo formed
4. embryo placed in mother
5 cloned organism genetically identical to the donor who gave nucleus
give 4 advantages to asexual reproduction (both plants/animals)
- genetically identical to parent
- characteristics predictable
- high survival rate
- can replace valuable organisms with identical ones
give 2 disadvantages to asexual reproduction for both plants/animals
- no opportunity to improve genetic qualities
2. more susceptible to infection/disease
give 1 disadvantage to asexual reproduction for plants
fewer offspring produced than by sexual reproduction
define transgenics
transfer of genes (of desirable characteristics) from species where they are naturally found to another species where they are not
give 4 advantages of GM/transgenics
- genes introduced that could’ve never been gained via selective breeding
- increase resistance to pests (reduce pesticides)
- increase yield
- a single characteristic introduced
give successful example of GM/transgenics
golden rice: genes from daffodile + a soil bacterium = increased vit. A in rice
give the 5 disadvantages of GM/transgenics
- pollen transfer to non GM crops
- transfer of resistant gene to bacteria
- reduction in native crop diversity
- link to food allergies
- increased costs for farmers
give an unsuccessful example of GM/transgenics
Bt crops: genes transferred from soil bacterium into corn crops (toxin produced to kill insects) = killed non-target species i.e. monarch butterfly
definition of yield
amount of crop per hectare
define energy subsidies
any input that increases productivity but requires the use of energy from fossil fuels
give 3 examples of energy subsidies
- pumping of irrigation H2O
- fuel for machinery
- manufacture of nitrate fertilisers/pesticides
T or F organic and subsistence farming are not labour intensive
false: very labour intensive!!
explain intensive farming
large amounts of inputs over a small area of land yield high per unit area
labour: low, Capital: high, Artificial fertilisers: high
which type of farming has the highest output?
intensive farming
which type of farming has the lowest productivity?
extensive
explain extensive farming
maximise yield by spreading available inputs over a large area of land
labour + capital + artificial fertilisers = low
what is the law of diminishing returns?
- increase the inputs, extra yield increase gets smaller
shows the link between efficiency + productivity
what are energy ratios?
measure of efficiency showing no. of food energy produced per unit of energy input
a system with high yields per unit energy has a higher….
energy ratio
a system with high productivity normally has high subsidies and so has low….
energy ratio
what is the formula to calculate energy ratio?
outputs/inputs
what is the formula to calculate energy efficiency (%)?
outputs/inputs x 100
name the 3 reasons why monocultures can increase productivity
- easy planting/weeding/harvesting etc.
- favours mechanisation (low labour)
- offers economies of scale (saving gained by increase level of production)
name the 4 disadvantages of monoculture
- reduces biodiversity (less niches)
- increase risk of soil erosion
- may lead to exhaustion of particular soil nutrients
- worst pest epidemics
if you have a high stocking/crop density________ is increased although can cause stress + _____ have greater effect
productivity, disease
definition of an autotroph
an organism which makes own nutrition from simple, inorganic substances i.e. producers
definition of an heterotroph
an organism which gains energy from eating other organisms
name the 3 ways to reduce food chain losses
- control movement
- temp control
- species selection
how does control of movement reduce food chain losses? + how is this done?
reduce movement, reduce respiration = more energy converted to growth i.e. place in cages
how does temp control reduce food chain losses?
keep organism warm, reduce energy lost as heat = more energy converted to growth
definition of food conversion ratio
measure of mass of food needed to produce a given mass of livestock growth
why is species selection important in reducing food chain losses?
- different species have different food conversion ratios
- lower the FCR = better conversion of food into biomass
