Flashcards in 10.8 : Changing Population Characteristics Deck (7):
Define selection pressures
Factors that affect the organisms chance of survival or reproductive success.
List and explain the steps in natural selection
1. There is variation in a population caused by differences in their genes due to different alleles caused by mutations.
2. Organisms whose characteristics are best adapted to selection pressure have an increased chance of surviving and successfully reproducing. Less well-adapted organisms die or fail to reproduce ( survival of the fittest )
3. Successful organisms pass the allele encoding the advantageous characteristic into their offspring.
4. This process is repeated for every generation. Over time, the proportion of individuals with the advantageous allele increases.
5. Overtime, this process can lead to the evolution of a new species.
List examples of evolution
Antibiotic - resistant bacteria
Explain how MRSA gained resistance.
When bacteria replicate, their DNA can be altered
A mutation arose that provided resistance to methicillin
When exposed to it, resistant individuals survived and reproduced, passing the allele for resistance on to their offspring
Describe and explain how peppered moths adapted and survived
Before industrial revolution = moths were pale coloured. Dark moths got eaten.
This was camouflage against light coloured tree bark.
During IR = trees become darker ( due to spot and loss of lichen cover caused by atmospheric pollutants )
Dark moths now better adapted as better camouflaged.
Dark moths reproduced and survived, increasing their population.
Due to cleaner air now, tree bark is lighter so pale moths survive more now
Describe how sheep blowflies developed resistance
They lay their eggs in faecal matter around a sheeps tail and cause sores ( can be fatal )
Pesticide diazinon used to kill them.
6 years later blowflies developed high level of resistance to it.
After investigation to blowflies with and without resistance, they discovered resistance allele in both, therefore, there was pre - existing resistance.