Harnessing biology Flashcards
Advantages of organic fertilisers
Improves soil structure
Greater range of minerals
Releases minerals over a longer period of time.
Less costly for farmer (already available on farm)
Disadvantages of organic fertilisers
Slow acting - has to decompose first
Bulkier, harder to apply to soil than inorganic
May contain pests
Advantages of inorganic fertilisers
Fast acting - mineral ions release immediately
Contents known
Easy to apply
Disadvantages of inorganic fertilisers
Can lead to eurtophication as fertiliser is soluble
Requires regular reapplication
Advantages of pesticides
Easily accessible and relatively cheap
Have an immediate effect
Kills the entire population of pests
Disadvantages of pesticides
Pests can develop resistance to them.
Non specific chemicals so can often kill other beneficial organisms (pollinating insects)
Chemicals can concentrate and accumulate at the top of the food chain, harming top predators.
Need for regular application so costly.
What pesticide kills insect pests?
Insecticides
What pesticide kills plant pests?
Herbicides
What pesticide kills fungal pests?
Fungicides
Give a brief description of how biological control happens
A species is introduced specifically to prey on the pest species. They never completely remove a pest, but keep it at lower levels. This can happen naturally.
Advantages of biological control
Pest will not become resistant.
Can target specific species, will only kill the pest.
Does not need to be repeatedly applied as organism will reproduce.
Long lasting.
Natural method - no pollution.
Disadvantages of biological control
Takes a long time to reduce pest population.
Cannot kill an entire population, some pests will always be present.
May not adapt to new environment.
Benefits of fish farming
Ability to selectively breed fish to ensure high-quality, fast-growing fish.
Can protect against predators.
Ability to control water quality.
Ability to control feeding to ensure rapid growth.
Explain how water quality is managed in fish farming
Water is filtered to remove waste and harmful bacteria to prevent diseases. Water is also cleaned to maintain high levels of oxygen for aerobic respiration.
Explain how diseases are controlled during fish farming
Antibiotics are given to fish to prevent spread of diseases which could otherwise spread quickly due to their close confinement. Kept in small numbers to minimise spread of disease. Higher chances of survival.
Explain how removal of waste products is used in fish farming
Water can be filtered to remove waste products such as faeces and sewage. Fences, nets, tanks are cleaned or location of fish is changed to ensure clean water.
Explain how quality and frequency of feeding is used in fish farming
Food is high in nutrients to ensure fast growth.
Fed frequently but in small amounts so they don’t overeat or start eating each other.
Explain how selective breeding is used in fish farming
Fish are separated by gender so farmers can choose to only allow fish with desired characteristic to reproduce (selective breeding). Ensures that the stock of fish is fast growing as these genes get passed on more frequently.
Define interspecific predation
Predation between different species.
Explain how interspecific predation is controlled in fish farming
Different species of fish are separated by fences, nets and tanks to prevent fighting.
Define intraspecific predation
Predation within the same species
Explain how intraspecific predation is controlled in fish farming
Fish are separated by size and age so they don’t eat each other or fight.
Explain how deforestation leads to leaching
Water is no longer taken up by plants and so begins to ‘run off’ from the soil into rivers and lakes. This water contains dissolved mineral ions (otherwise absorbed by the plant). Mineral ions are removed from the soil (loss of nutrients) and some cause eutrophication
Explain how deforestation leads to soil erosion
Water running off deforested areas may carry away topsoil leading to erosion. Due to deforestation, less roots in soil so topsoil is not held in place. Topsoil is most fertile, mineral ion rich so when it is lost, land is difficult to use for crop growth and reduces chances of plants re-growing.
Explain how deforestation can lead to droughts
Plants carry out transpiration. The evaporated water from transpiration moves into atmosphere and eventually makes rain. Deforestation breaks this cycle so water doesn’t end up in the atmosphere so rain doesn’t occur. Leads to droughts.
Explain eutrophication
Nitrates are absorbed by the green algae in the water.
They multiply rapidly and may cover surface of water. This is called algal bloom.
This blocks out the sunlight for other plants in the lake/river.
The plants can’t photosynthesise so they die.
The algae on top eventually die.
The dead remains provide food for bacteria. The bacteria multiply rapidly.
Large population of bacteria respire increasing biological oxygen demand (B.O.M), using up oxygen in the water.
Decreases level of oxygen in the water and results in the death of other organisms in the water as they cannot respire aerobically.
Explain how sewage pollutes water
Sewage provides a good source of food for the bacteria. The bacteria multiply rapidly. Large population of sewage respire increasing B.O.D, using up oxygen in the water. This decreases the level of oxygen and results in the death of other organisms in the water, as they cannot respire aerobically.
Explain how greenhouses and polythene tunnels provide enhanced conditions for plants to grow
Transparent material allows natural light in for sufficient photosynthesis.
Greenhouse effect raises temperature.
Burning fossil fuels or wood increases temperature when external temperature is too low, also provides carbon dioxide and water vapour.
Water vapour maintains a moist atmosphere so reduces water loss by transpiration.
This increases rate of photosynthesis so increases the yield.
Benefits of selective breeding
Desirable characteristics emerge faster.
Humans can choose desirable characteristics.
Problems with selective breeding
Population is more susceptible to disease.
Reduces variation.
