Biological Resources Flashcards
Lactobacillus in yoghurt making
- Equipment sterilised to kill any unwanted bacteria
- Milk is pasteurised (heated) at 85 degrees Celsius to kill any natural bacteria the milk contains
- Milk is homogenised - dispersed fat into globules (makes smaller)
- Milk is cooled to 30-40 degrees to stop bacteria being killed. It is mixed with lactobacillus - this digests milk proteins and ferments lactose, producing lactic acid
- Milk is incubated at this temperature
- During fermentation, the proteins in the milk denature - not the bacteria due to a drop in pH - this results in the mixture thickening. Thickened yoghurt is stirred and cooled to 5 degrees. This halts the action of bacteria
- Flavourings, colourings and fruit can be added before packaging
What affects crop yield
the rate of photosynthesis, which is affected by water, light, carbon dioxide and temperature
method to create ideal conditions for photosynthesis
using a greenhouse
how do greenhouses help create ideal conditions for photosynthesis
- keeping plants enclosed makes it easier to keep them free from pests and disease
- helps farmers control water supplied to crops
- commercial farmers often supply artificial light even after the sun goes down to give plants more time to photosynthesis
- greenhouses trap the suns heat to keep plants warm
- in winter, a heater can be used to keep temperature at an ideal level
- can increase amount of CO2 available (e.g. paraffin heater to heat the place which released CO2 as a by product)
what is used on plants to ensure crops have enough minerals
fertilisers:
plants need certain minerals (e.g. nitrogen, potassium and phosphorus) to make proteins to allow them to grow
sometimes there are not enough minerals available, so farmers use fertilisers to provide more and increase crop yield
how does pest control stop pests eating crops
- pests include microorganisms, insects and mammals
- pests that feed on crops are killed using various methods of pest control
- this means that less plants are damaged or destroyed, increasing crop yield
what are pesticides
form of chemical pest control
often poisonous to humans, so must be used carefully to keep amount of pesticide in food below a safe level
some pesticides also harm wildlife
biological control
alternative to using pesticides
means using other organisms to reduce the number of pests, either by encouraging wild organisms or adding new ones
the helpful organisms could be predators, parasites or disease-causing
pesticides vs biological control
- biological control can often have a longer lasing effect than pesticides and be less harmful to wildlife
- however introducing new organisms can cause problems (e.g. cane toads were introduced to Australia to eat beetles, but they are now a major pest themselves as they poison native species that eat them)
what do fermenters do
can provide optimum conditions for microorganisms
how do fermenters work - pH monitoring
pH monitored and kept at optimum level for enzymes to work efficiently
this keeps the rate of reaction and product yield as high as possible
how do fermenters work - nutrients
nutrients needed by the microorganisms for growth are provided in the liquid culture medium
how do fermenters work - paddles
microorganisms are kept in contact with fresh medium by paddles that circulate the medium around the vessel
this increases product yield as the microorganisms can always access the nutrients needed for growth
how do fermenters work - temperature
temperature is monitored and kept at an optimum level
a water-cooled jacket makes sure it doesn’t get too hot so that the enzymes do not denature
how do fermenters work - sterilised
vessels are sterilised between uses with superheated steam to kill unwanted microbes
having aseptic conditions increases the product yield because the microorganisms aren’t competing
it also means that the product doesn’t get contaminated
how do fermenters work - oxygen
if the microorganisms need oxygen for respiration, its added by pumping in sterile air
this increases the product yield because the microorganisms can always respire to provide the energy for growth
key features of fermenters
water-cooled jacket
paddles
superheated steam
pumped sterile air
culture medium
yeast in breadmaking
- initially, yeast will respire aerobically, producing carbon dioxide and water
- when air runs out, conditions become anaerobic, releasing carbon dioxide and ethanol - known as fermentation
- the yeast produces enzymes that break down the starch, releasing sugars that can be used for anaerobic resp.
- the carbon dioxide is trapped in bubbles in the dough, as the pockets of gas expand, the dough begins to rise
- the dough is then baked in an oven where the yeast continues to ferment until the temperature of the dough rises enough to kill the yeast
- any ethanol produced is evaporated away
- the yeast dies meaning the bread stops rising, but pockets are left in the break where the CO2 was trapped
selective breeding
the process by which humans breed plants/animals with desired characteristics
they want to obtain bigger food yields from crops and stock animals to increase food supply
process of selective breeding
- humans select desired characteristics
- cross breeding of male and female with desired characteristics
- selection of offspring showing desired characteristics
- repeat the process over many generations until allele for desired characteristic increases in frequency
fish farming key features
- fish are kept in cages in the sea - less energy from swimming used
- cage also protects them from interspecific predation
- fed a diet of pellets that are controlled to maximise the energy they get so the fish grow more
- young fish are put in special tanks to survive
- younger fish are separated from older fish to prevent intraspecific predation
- fish in cages are more prone to diseases and parasites - biological pest control can be used
- fish can be selectively bred to produce faster growing, less aggressive fish
what are fish farms designed for
to produce as many fish as possible
fish being farmed in tanks
conditions can be controlled:
- water monitored to ensure temp, pH and O2 level is ok
- easy to control the amount and type of food supply
- water can be removed and filtered to get rid of waste food and faeces - keeps water clean for fish and avoids pollution
what can enzymes do to DNA
cut up DNA or join DNA pieces together
