Biology- Section 9
- Created by: emmaaaaa
- Created on: 18-05-13 09:59
Increasing Crop Yield
You can artificially create ideal conditions for photosynthesis for a better crop yield:
- Keeping plants in glasshouses to keep free from pests and diseases
- Give artificial light after Sun goes down so plants have more time to photosynthesise
- Glasshouses trap Sun's heat keep warm, in winter also use heater keep temperature ideal
- increase level carbon dioxide using paraffin heater, as carbon dioxide a by-product
Fertilisers can be used to ensure the crops have enough nutrients:
- Plants need some elements to make compounts like proteins
- If not enough available, their growth and life processes are affected
- Sometimes elements not in soil as been used by previous crop
- Fertilisers replace missing elements or provide more to increase crop yield
Pest control can stop pests eating crops:
- Pesticides- often poisonous to humans, used carefully on food can harm other wildlife
- Biological control- use other organisms reduce number of pests can have longer lasting effects
Yeast and Making Beer
Yeast respires aerobically (with oxygen) to turn sugar into carbon dioxide.
Yeast respires anaerobically (without oxygen) to turn sugar into carbon dioxide and alcohol.
- Beer usually made from grail- e.g. barley
- Grains allowed germinate and starch broken into sugar and enzymes
- Dried in a kiln, called malting then mashed and water added make sugary solution
- Solution sieved and hops added give bitter flavour
- Yeast added and mixture incubated, ferments sugar into alcohol
- Rise concentration of alcohol starts kill yeast so fermentation slow down
- Different yeast tolerate different levels alcohol make stronger/weaker beer
- Beer drawn off, sometimes clarifying agent added make it clearer
- Beer pasteurised- heated kill any yeast left then ready to sell
Selective Breeding
Organisms are selectively bred to develop the best features:
- Maximum yield of meat, milk, grain etc.
- Good health and disease resistance
- In animals: temperament, speed, fertility, mothering skills
- In plants: pretty flowers, nice smell
Increase productivity of cows:
- Cows selectively bred produce offspring higher yield in meat
- Animal characteristics increase meat yield selected and bred together
- The offspring best characteristics then bred, continued several generations
Increase crop yield:
- Combine 2 desired characteristics
- Tall wheat good grain but easily damaged, dwarf wheat resist damage lower grain yield
- Plants cross-bred and best resulting cross-bred again, new variety wheat good characteristics
Fish Farming
Fish Farming cages in the sea like in Scotland:
- Fish in cages in sea stop using energy swimming
- Also protects from interspecific predation- being eaten by birds and seals
- Fed on food pellets carefully controlled maximise amount energy get
- Better quality food, quicker and bigger fish will grow
- Young fish reared special tanks ensure many as possible survive
- Keep younger fish separate big fish so not eat small fish
- Fish kept in cages more prone to disease and parasites e.g. sea lice
- Can use pesticides but avoid pollution biological control used instead e.g. wrasse fish eat lice
- Fish can be selectively bred, produce less agressive, faster growing fish
Fish can be farmed in tanks:
- Fresh water fish e.g. carp farmed in ponds/ tanks so conditions controlled
- Water monitored check temperature and pH and oxygen levels good
- Easy control how much food supplied and give exactly right sort food
- Water can be removed or filtered to get rid of waste to keep clean and to avoid pollution
Genetic Engineering
Enzymes often used to cut DNA and join it back together:
- Restriction enzymes recognise certain sequences of DNA and cut the DNA there
- Ligase enzymes join the DNA together
- When 2 different parts of DNA are joined together it is known as recombinant DNA
Vectors are used to insert DNA to other organisms:
- Vector used transfer DNA into a cell- plasmids and viruses
- DNA want to insert cut out with restriction enzyme, vector DNA cut open using same enzyme
- Vector DNA and DNA inserting mixed with ligase enzyme- joins to form recombinant DNA
- Recombinant DNA inserted other cells
- Cells can use gene inserted to make protein you want e.g. bacteria contain gene human insulin be grown in fermenter produce insulin people with diabetes
Genetic Engineering
Plants can be genetically modified to improve food production:
- Insect resistant- spray less pesticides so less wildlife harmed
- Herbicide resistant- spray herbicides kill weeds not affect crop itself
- Concerns over GM food- transplanted genes may get into environment- weed pick up herbicide resistant gene and make new 'superweed'
- Transplanted genes could affect food chains or human health also
- Changing genes could cause unforseen problems which are passed on to future generations
Cloning
Tissue culture (micropropagation) is used to clone plants
- Plant with desirable characteristics selected to be cloned, small pieces taken from tips of stems and side shoots of plant
- The explants are sterelised to kill microorganisms
- They are then grown in vitro- placed in petri dish with nutrients and growth hormones
- Cells divide and grow into small plants, if large quantity needed further explants can be taken from spall plants until enough produced
- Small plants planted in soil and put into glasshouses and develop genetically identical to orginal plant
Cloning adult mammals can be done by transplanting a cell nucleus like Dolly the sheep:
- Nucleus of sheep egg cell removed making enucleated cell
- Diploid nucleus inserted in its place- nucleus mature udder cell different sheep
- Cell stimulated to start dividing via mitosis as if normal fertilized cell
- Dividing cell implanted into uterus of another sheep to develop until ready to be born
- Result was dolly, clone of sheep- other animals can be cloned similar method.
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