3.4.4 Genetic Diversity And Adaptation Flashcards
What is genetic diversity?
The total number of different alleles within a population
What is a gene pool?
The total number of all the alleles of all the individuals in a population at a set time
What is allele frequency?
The proportions of the different alleles in the gene pool
Define population.
Group of individuals of the same species that live in the same place at the same time
Define species.
Individuals that can be interbred to produce fertile offspring
How do individuals within a species differ?
In the combination of their alleles
They have the same genes
Why is genetic diversity good for survival within a population?
There is more variety and so more alleles
If the environment changes there is higher chance if there beef a gene that aids survival within the species
Define gene.
A section of DNA that codes for one polypeptide
What is natural selection?
Organisms that have certain alleles that make them better adapted to their environment survive and breed which increases the frequency of those advantageous alleles in the next generation
What can allele frequency?
Difference between the reproductive success of individuals
Changes in environment
Describe the process of natural selection.
Random mutation of an allele results in a new allele of a gene
If the gene is advantageous the individual will be more likely to survive
They obtain better resources and so live longer so have more time to breed
The individual reproduction get successfully will pass on the allele to offspring
The frequency of this allele in the population increases as those who possess it survive and reproduce
What are the key stages of natural selection?
Variation Mutation Environmental changes Some survive Reproduce Allele
What are the two types of selection?
Directional selection
Stabilising selection
What is direction selection?
Where individuals that vary in one direction from the mean of the population are favoured
Changes the characteristics of the population
What is stabilising selection?
Average individuals are favoured
Preserves the characteristics of the population
Define phenotype.
The observable physical and biochemical characteristics of an organism
How does directional selection occur?
Environment changes
Phenotypes best suited survive
Some individuals to the left or right of the mean will have a better suited phenotype
These individuals are more likely to survive, breed and pass on the phenotype to offspring
Over time the mean moves in the direction of these individuals (as they contribute more offspring than others)
How can bacteria become resistant to antibiotics?
Bacteria mutates
New strain is resistant to antibiotics
New strain reproduces more quickly until it is the majority population
How did mutated bacteria resist penicillin?
A mutation occurred in the allele of a gene in a bacterium that allowed it to make a new protein that breaks down penicillin before it can kill the bacteria
The enzyme is called penicillinase
How did the bacteria that could produce penicillinase become the majority population?
It broke down the penicillin
The penicillin killed the non resistant bacteria
The resistant bacteria reproduced by binary fission
The frequency of the allele that enabled the production of penicillinase increased as the others decreased
When does stabilising selection occur?
When environmental conditions remain constant
Individuals with protons closed to the mean are favoured
What are the three types of adaptation?
Anatomical
Physiological
Behavioural
