Toxins can build up in a food chain by chemicals used by farmers, two common ones inclue PCB (chemicals used inslating electrical equipment) and DDT (powerful insectacide) - these two pollutants enter food chain by plankton - microscopic plants and animals. They cannot be digested properly and are stored as fat in the body, they can kill the bigger consumers as toxic. Restriction (cuts) enzymes and ligase (glues) enzymes are used when handling DNA . Assaying - transgenic organisms (new genes put in it) get the new gene and therfore to seperate the GE organisms, a marker gene (antibiotic resistant) gane is also put in so the ones that have taken up the gene shall survive when put on an antibiotic agar plate. GE in plants/foods means that plants can be modified to be resistant to diseases and the effects of herbicides - weedkillers- and also can grow with bigger yeilds etc. An advantage of this would be we can make plants that produce certain vitamn helping people survive and also means we can grow crops in famine soil conditions. But cons ; may not be safe to eat in long term; the plants may crossbread with there new genes creating unexpected results could be dangerous messing with nature; GM seeds are expensive and have to be bought yearly. Amoeba and salmon both find it hard to maintian there water concentration, Amoba lives in freshwater (dilute) their cytoplasm is more concetrated so they absorb lots of water by osomosis, to prevent bursting they pump water into small vacuoles by active transport and small vacuoles fuse into a larger contrractile vacule which empties water. Salmon live in sea/salt water and freshwater during life, in salt water, too concentrated than their cytoplasm so lose a lot of water so they do concentrated urine, they drink lot of seawater and excrete salt from gills. Adult salmon breed upstream in freshwater and lay eggs their, they absorb a lot more water so they do very dilut urine to maintain water levels.
pathogens spread very quickly as right conditions in human body and they can feed on food and poisin it as they make toxins as feed. Disese spreads quick after disasters as sewage systems mix -so dirty water, electric supply limited so cant heat food up properly, fridge and freezers rationed supply so food decays, hospital may be destroyed or roads so disease passed airbourne. have to use aseptic techniqques when handling bacteria, heat equipment in autoclave to kill bacteria, surface disinfectant, wash hands, wear gloves, destroy bacteria after experiment, dont open lids of dishes. Yeast is a single celled organism and budding is asexual and identicle as nucleus copied, they need sugar, removal of waste lioke alcohol as can poisen yeast, temp of 40 is opt.