10.8 Changing Population Characteristics

What type of process is evolution?

dynamic process

When is evolution occurring?

all the time

What are sectional pressures?

factors that affect the organism’s chance of survival or reproductive success

What is Reproductive success?

the ability to produce fertile offspring

What are exposed to selection pressures?

all organisms

What organisms are more likely to survive and reproduce?

organisms that are best adapted to their environment

What do these adaptations become more common in the population as a result of?

natural selection

What is less likely for organisms that are poorly adapted?

less likely to survive and reproduce

What won’t poorly adapted organisms be able to do due to them being less likely to survive and reproduce?

their characteristics won’t be passed on to the next generation - less of the population will display these characteristics

Natural selection 1: What do organisms within a species show?

variation in their characteristics

Natural selection 1: what is this variation in their characteristics caused by?

differences in their genes (genetic variation)

Natural selection 1: an example of genetic variation?

they may have different alleles for a particular characteristic

What can new alleles arise by?

mutation

Natural selection 2: examples of selection pressures (3)?

predation, competition (for mates and resources) or disease

Natural selection 2: who will have an increased chance of surviving and successfully reproducing?

organisms whose characteristics are best adapted

Natural selection 2: What is less well-adapted organisms dying or failing to reproduce while the best adapted survive and successfully reproduce known as?

survival of the fittest

Natural selection 3: what do the successful/best organisms pass on to their offspring?

the allele encoding the advantageous characteristic

Natural selection 3: what is the less well-adapted organism less likely to successfully pass on?

the non-advantageous allele

Natural selection 4: when is this process repeated?

for every generation

Natural selection 4: what increases over time?

the proportion of individuals with the advantageous adaptation

Natural selection 4: Therefore what does the frequency of in the gene pool increase?

the allele that codes for the particular characteristic

Natural selection 5: over what amount of time can the process of natural selection lead to the evolution of new species?

over very long periods of time, many generations and often involving multiple genes

What always occurs in a population?

genetic variation (due to sexual reproduction)

Specation?

the evolution of new species

In what circumstances can specation only occur in?

when there is isolation/separation of the populations

What are there different types of in different environments?

different selection pressures

A modern example of evolution?

Antibiotic-resistant bacteria

A bacteria that has developed resistance to many antibiotics?

Methicillin-resistant Staphylococcus aureus (MRSA)

At what pace to bacteria reproduce at?

reproduce very rapidly - evolve in a relatively short time

What can cause the bacteria to die when they replicate?

the DNA can be altered - usually results in bacteria dying

What arose in some S.aureus bacteria that provided resistance to methicillin?

a mutation

What happened when this specific bacteria was exposed to the antibiotic methicillin?

the resistant individuals survived

What did the resistant S.aureus who survived pass on to their offspring?

the allele for resistance

What bacteria died when exposed to the antibiotic (Methicillin)?

the non-resistant bacteria

Over time what type of bacteria increased?

the antibiotic (Methicillin) resistant bacteria (S.aureus)

Peppered moths scientific term?

Biston betularia

What causes changes in allele frequency in peppered moths?

dramatic changes in the moth’s environment in the 19th century

What colour were most peppered moths before the industrial revolution in Britain?

most were pale coloured

Why were most peppered moths pale coloured then?

to camouflage them against the light-coloured tree bark

Why is camouflage a desirable characteristic?

increases chance of survival - predators can’t find them and kill them

What happened to dark peppered moths before the industrial revolution?

easily spotted by birds and eaten

What are the different colourings of the moths due to?

different alleles - genetic variation

What happened to trees during the industrial revolution?

many trees became darker

Why did many trees become darker (2)?

partly due to being covered in soot and partly due to the loss of lichen cover

Why was there the loss of lichen cover on trees?

caused by increased atmospheric pollutants

Why were the dark peppered moths better adapted once the trees became darker?

they were now more highly camoflagued

What were more dark peppered moths now able to do?

survive and reproduce

What did the dark peppered moths surviving and reproducing increase the frequency of?

dark moths and the ‘dark’ allele in the population

What did the number of dark peppered moths become much higher than, after a few years?

the number of dark peppered moths close to industrial towns and cities became much higher than pale peppered moths

When have there been steps taken to do since The Clean Air Act?

steps to improve air quality in towns and cities and to reduce the levels of pollution released from factories

When was The Clean Air Act?

1956

Due to the cleaning of the air causing the majority of trees in the UK being lighter coloured again, what has the frequency of increased?

the frequency of the pale allele in the moth gene pool has increased

Scientific term for Sheep bowflies?

Lucilia cuprina

Where do Sheep bowflies lay their eggs?

in faecal matter around a sheep’s tail

What do the larvae cause when they hatch?

cause sores

What is condition when the larvae hatches in the faecal matter around a sheep’s tail and causes sores on the sheep?

flystrike

What does ‘flystrike’ normally become if left untreated?

normally becomes fatal

What was used to kill the bow flies and prevent the condition in Australia in the 1950s?

the pesticide diazinon

What kind of pesticide is the pesticide diazinon?

an organophosphate pesticide

Within 6 years what had bow flies developed in Australia?

a high level of resistance to diazinon

How had the bow flies developed a high level of resistance to diazinon?

individual insects with resistance survived exposure to the insecticide, and passed on this characteristic through their alleles, allowing a resistant population to evolve

What did scientists do to investigate how this evolution occurred so quickly?

they extracted DNA from a sample of 70-year-old bowflies

Where was the sample of 70-year-old bowflies kept at?

the Australian National Insect Collection

The two Australian bowflies that were studied?

Lucilia cuprina and the closely related Lucilia sericata

What did the researchers compare when studying these Australian bowflies?

the bowflies’ resistance genes before and after the introduction of the pesticide

In what bowflies did the scientists find the diazinon resistance in?

present in the DNA of the modern species - wasn’t found in the DNA of 70-year-old bowflies

What did they perform this same investigation with?

Malathion

What is Malathion?

another organophosphate pesticide

When doing the experiment with malathion and not diazinon what was found in both the old and modern blowflies?

resistant alleles

What does the Malathion resistant alleles being present in both the old and modern blowflies show?

that there was pre-existing resistance to this chemical Malathion

What did the scientists conclude contributed to the development of diazinon-resistance?

pre-adaptation

Pre-adaptation?

when an organism’s existing trait is advantageous for a new situation

What did the pre-existing resistance (to Malathion) allow the flies to do?

rapidly develop resistance to organophosphate chemicals in general - and ultimately a specific diazinon-resistance allele

What may the existence of pre-adaptation in an organism help researchers to predict?

potential insecticide resistance in the future

How does most evolution occur?

as a negative result of selection pressures

What have some organisms evolved due to, that have arisen in their environments?

due to opportunities that have arisen in their environments

An example of an organism that has evolved due to opportunities that have arisen in their environments?

Flavobacterium

Where have scientists found a strain of Flavobacterium living?

waste water from factories that produce nylon 6

What is nylon 6 used to make (2)?

objects like toothbrushes and violin strings

What has this strain of Flavobacterium evolved to do?

to digest nylon

How is the bacteria digesting nylon beneficial to humans?

they help to clear up factory waste

What does the Flavobacterium use to digest nylon?

enzymes known as nylonases

What are nylonases unlike?

any enzymes found in other strains of Flavobacterium

What don’t nylonases help the Flavobacterium to digest?

any other known material

Why are nylonases beneficial to the bacteria?

it provides them with another source of nutrients

What occurred to produce the enzymes nylonase?

a gene mutation

What do scientists believe this gene mutation that produced nylonase is a result of?

gene duplication, combined with a frameshift mutation

Frameshift mutation?

an insertion or deletion of DNA bases that causes the genetic code to be read incorrectly