Resistance to many things can be caused in other animals due to the actions of humans for example there is now a dominant gene in rats which is causing them to be resistant to the warfarin. Homozygoes dominant indviuals have a massive requirement for vitamin K so it is better to be a hetrozygote and have resistance but less need for vitamin K.
Resistance to antibiotics is also a major problem with bacteria such as MRSA becoming resistant to antibiotics. Another concern is that these genes are carried in plasmids and can be transfered to other bacteria of the same species even if they have never been exposed to the antibiotic. This is why is is very important that antibiotics are not over used and that if you are on a course of antibiotics that they are compeleted so that none of the bacteria can suvive and pass on resistance to others. This occurs in farm animals as well as humans.
humans have been able to alter the milk yeild by breeding animals which produce the highest milk yeilds in a community.This maybe done by in breeding, which is breeding animals that are quite closly related, this is in breeding and outbreeding is where you breed animals together which are not related.In breeding means that you risk bring together 2 recessive alleles which may not be favourable.Where as out breeding creates hybrid vigour.
Extinction is where a species is lost for ever and this has been increasing in recent years due to loss of habitats/food sources hunting and competiton from introduced animals an example is the cane toad in australia.It is now considered that all animals and plant could be of help to us as a food source or as a source for chemicals and disease resistant genes…