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Genetic diversity - A Level AQA powerpoint

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Genetic diversity
Genetic diversity
Genetic diversity –
Genetic diversity
Genetic diversity – the number of alleles in a species or population
Genetic diversity
Genetic diversity – the number of alleles in a species or population
Natural selection acts to increase the number and proportion of
advantageous alleles within a population.
Genetic diversity
Allele –
Genetic diversity
Allele – different versions of the same gene
Genetic diversity
Allele – different versions of the same gene
Species –
Genetic diversity
Allele – different versions of the same gene
Species – a group of organisms with similar morphological and
physiological characteristics that are able to breed together to produce
fertile offspring
Genetic diversity
Allele – different versions of the same gene
Species – a group of organisms with similar morphological and
physiological characteristics that are able to breed together to produce
fertile offspring
Population –
Genetic diversity
Allele – different versions of the same gene
Species – a group of organisms with similar morphological and
physiological characteristics that are able to breed together to produce
fertile offspring
Population – a group of organisms of one species living in the same
place at the same time
Genetic diversity
In which two ways can the genetic diversity of a population be
increased?
Genetic diversity
In which two ways can the genetic diversity of a population be
increased?
• Mutations in DNA to form new alleles
• Different alleles being introduced into the population due to
migration and reproduction – known as gene flow.
Genetic diversity
Genetic diversity is what drives natural selection. There are three key
stages to natural selection:
Genetic diversity
Genetic diversity is what drives natural selection. There are three key
stages to natural selection:
1. Individuals with more advantageous characteristics that make them
more adapted to the environment/ecosystem are more likely to
survive.
Genetic diversity
Genetic diversity is what drives natural selection. There are three key
stages to natural selection:
1. Individuals with more advantageous characteristics that make them
more adapted to the environment/ecosystem are more likely to
survive.
2. These individuals are therefore more likely to reproduce.
Genetic diversity
Genetic diversity is what drives natural selection. There are three key
stages to natural selection:
1. Individuals with more advantageous characteristics that make them
more adapted to the environment/ecosystem are more likely to
survive.
2. These individuals are therefore more likely to reproduce.
3. The next generation of the population is therefore more likely to
have a higher proportion of their alleles coding for those
advantageous characteristics.
Genetic diversity
Over generations, the population will have a much higher proportion of
the advantageous allele, meaning it will lead to it becoming more
common. This is what evolution is.
Genetic diversity
Over generations, the population will have a much higher proportion of
the advantageous allele, meaning it will lead to it becoming more
common. This is what evolution is.
Evolution –
Genetic diversity
Over generations, the population will have a much higher proportion of
the advantageous allele, meaning it will lead to it becoming more
common. This is what evolution is.
Evolution – gradual changes to a species overtime.
Genetic diversity
Over generations, the population will have a much higher proportion of
the advantageous allele, meaning it will lead to it becoming more
common. This is what evolution is.
Evolution – gradual changes to a species overtime.
Adaptation and selection are key factors to evolution.
Evolution can lead to huge diversity within species and between
species.
Bottlenecking
Genetic bottlenecking can reduce genetic diversity, and therefore
reduce the amount of natural selection taking place.
Bottlenecking
Genetic bottlenecking can reduce genetic diversity, and therefore
reduce the amount of natural selection taking place.
Genetic bottlenecking –
Bottlenecking
Genetic bottlenecking can reduce genetic diversity, and therefore
reduce the amount of natural selection taking place.
Genetic bottlenecking – an event that cause a big reduction in a
population, causing the genetic diversity to decrease
Bottlenecking
Genetic bottlenecking can reduce genetic diversity, and therefore
reduce the amount of natural selection taking place.
Genetic bottlenecking – an event that cause a big reduction in a
population, causing the genetic diversity to decrease
When the individuals in the species die, the number of different alleles
in the gene pool of the species decreases, so genetic diversity
decreases too.
Bottlenecking
This leaves a small population with a small gene pool.
These individuals will reproduce and form a larger population
(providing they are suitable adapted to the environment).
Bottlenecking
One example of bottlenecking is that off moths.
In the industrial revolution, many of the trees were polluted with soot,
meaning white moths were more likely to be seen by predators.
Bottlenecking
This gave an advantage to the darker coloured moths, meaning the
gene pool was vastly decreased. Now, most of this species of moth are
darker in colour due to this event.
Bottlenecking
Genetic bottlenecking can be described by the Founder effect.
Bottlenecking
Genetic bottlenecking can be described by the Founder effect.
What is the Founder effect?
Bottlenecking
Genetic bottlenecking can be described by the Founder effect.
What is the Founder effect?
The Founder effect describes what happens when a few individuals of a
species start a new population from a small gene pool.
Bottlenecking
The frequency of alleles in the new population may be vastly different
to the frequency of alleles in the original population.
Bottlenecking
The frequency of alleles in the new population may be vastly different
to the frequency of alleles in the original population.
The most common example, is that a rare allele in the original
population is now more frequent in the new population. This can lead
to a higher incidence of genetic disease.
Bottlenecking
The Amish population descended rom a small number of Swiss
individuals who migrated to North America. Their population has a
small gene pool, so there was little genetic diversity.
The Amish typically have remined isolated since their migration due to
religious beliefs, so few new alleles have been introduced into the
population. This has lead to the population having a high incidence of
genetic disorders such as dwarfism and Angelman syndrome
Bottlenecking
Typically, an allele will only become the most common in a population,
providing it is not disadvantageous to the livelihood of the individuals
(meaning they can reproduce and pass on their alleles before being
killed/dying).
Natural selection
What are the three key stages to natural selection?
Natural selection
What are the three key stages to natural selection?
1. Individuals with characteristics that make them more adapted to
the environment/ecosystem are more likely to survive.
2. These individuals are more likely to reproduce.
3. The next generation of the population is more likely to have a
higher proportion of their alleles coding for those advantageous
characteristics.
Natural selection
Natural selection leads to a population becoming better adapted to the
environment/ecosystem.
There are three main adaptations you need to be aware of:
1. Behavioural adaptations –
Natural selection
Natural selection leads to a population becoming better adapted to the
environment/ecosystem.
There are three main adaptations you need to be aware of:
1. Behavioural adaptations – the ways in which organisms act to
increase their chances of survival and reproduction –
Natural selection
Natural selection leads to a population becoming better adapted to the
environment/ecosystem.
There are three main adaptations you need to be aware of:
1. Behavioural adaptations – the ways in which organisms act to
increase their chances of survival and reproduction – such as a
mating ritual.
Natural selection
2. Physiological adaptations –
Natural selection
2. Physiological adaptations – biochemical changes within an
organism’s body to increase its chance of survival –
Natural selection
2. Physiological adaptations – biochemical changes within an
organism’s body to increase its chance of survival – such as some
animals hibernating over winter. This decreases their metabolic
rate, meaning energy can be conserved so they don’t have a high
demand for energy from food when food is in short supply.
Natural selection
3. Anatomical adaptations –
Natural selection
3. Anatomical adaptations – structure changes within an organism’s
body that increase its chance of survival –
Natural selection
3. Anatomical adaptations – structure changes within an organism’s
body that increase its chance of survival – wolves evolved to have
‘puppy dog eyes’, meaning they were more likely to be given scraps
of food by humans, and therefore more likely to survive.
Natural selection
There are different types of natural selection that can lead to different
allele frequencies in a population.
Natural selection
There are different types of natural selection that can lead to different
allele frequencies in a population.
What are the two main types of selection you need to know?
Natural selection
There are different types of natural selection that can lead to different
allele frequencies in a population.
What are the two main types of selection you need to know?
• Directional selection
• Stabilising selection
Directional selection
Directional selection –
Directional selection
Directional selection – where individuals with alleles for an extreme
type of characteristic are more likely to survive and reproduce.
Directional selection
Directional selection – where individuals with alleles for an extreme
type of characteristic are more likely to survive and reproduce.
This typically is a response due to environmental change.
Directional selection
Directional selection – where individuals with alleles for an extreme
type of characteristic are more likely to survive and reproduce.
This typically is a response due to environmental change.
The most common example is bacteria evolving antibiotic resistance.
Directional selection
It happens over four stages:
Directional selection
It happens over four stages:
1. Individuals in the population have alleles coding for resistance to an
antibiotic.
Directional selection
It happens over four stages:
1. Individuals in the population have alleles coding for resistance to an
antibiotic.
2. These individuals are more likely to survive if the population is
exposed to the antibiotic than those without the allele.
Directional selection
It happens over four stages:
1. Individuals in the population have alleles coding for resistance to an
antibiotic.
2. These individuals are more likely to survive if the population is
exposed to the antibiotic than those without the allele.
3. The resistance bacteria survive and reproduce, passing the resistant
allele on to the new generation so it increases in frequency.
Directional selection
It happens over four stages:
1. Individuals in the population have alleles coding for resistance to an
antibiotic.
2. These individuals are more likely to survive if the population is
exposed to the antibiotic than those without the allele.
3. The resistance bacteria survive and reproduce, passing the resistant
allele on to the new generation so it increases in frequency.
4. After many generations, the antibiotic resistant allele is the most
common allele in the population.
Directional selection
Number of individuals
Offspring (over generations)
Number of individuals
Parents
low
Antibiotic resistance
high
low
Antibiotic resistance
high
Stabilising selection
Stabilising selection –
Stabilising selection
Stabilising selection – individuals with alleles for characteristic in the
middle of a range are more likely to survive and reproduce.
Stabilising selection
Stabilising selection – individuals with alleles for characteristic in the
middle of a range are more likely to survive and reproduce.
This occurs when the environment is table, reducing the range of
possible characteristics.
The most common example is human birth weight.
Stabilising selection
Humans typically have a range of birth weights, but there can be issues
at the extremes:
• Small babies are less likely to survive, typically they find it difficult to
maintain their body temperature.
• Large babies can be difficult to birth, meaning there can be
complications, and large babies are also less likely to survive.
This means medium sized babies are most favourable, so the weight of
human babies shifts to the middle of the range.
Stabilising selection
Number of individuals
Offspring (many generations)
Number of individuals
Parents
light
Weight of baby (oz)
heavy
light
Weight of baby (oz)
heavy
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