T4L2: NATURAL SELECTION Flashcards
Suggest how natural selection has led to the evolution of a certain species into the condition that it is today
VMSASIAS
V= Variation
In a species there is genetic variation
M= Mutation
This variation is caused by mutations to DNA
S= Selection pressure
There was a selection pressure of (specific to q)
A= Advantage
Certain organisms had an advantage in the face of this sp
S= Survival
This made these organisms better suited to survive
I= Inheritance
This means that when these organisms reproduce their offspring would inherit these preferable alleles that best suited the environment/sp
A= Allele frequency
The frequency of the allele that codes for said-characteristic would increase within this population
S=Speciation
Speciation may occur when this group’s genes are so different to the others in the population that they can no longer breed to produce fertile offspring
Name the three types of variation
Stabilising
Directional
Disruptive
Explain what stabilising variation is
When both extremes are not favoured/intermediates ARE favoured
E.g peacock tail - too small won’t attract a mate and too big and you will be eaten
BEST OF BOTH WORLDS
also e.g baby weight
Explain directional variation
When one extreme of a range of characteristics is favoured
e.g the peppered moth
Only dark ones survived when the trees were dark so this increased the frequency of ‘dark’ alleles
Explain disruptive variatiob
Where two extreme phenotypes are both favoured
This occurs when the organism is found in different areas with completely different conditions
e.g in the rainforest GREEN and BROWN caterpillars would be found as some would camoflague in the soil and some in the leaves
THIS IS ALSO GEOGRAPHICAL ISOLAITON
What are the two Hardy-Weinburg equations and provide a key
p+q=1
p^2 + 2pq + q^2= 1
p= number of dominant alleles in a popu
q= numbe rof recessive alleles in a popu
p^2= number of AA organisms in a popu
2pq= number of Aa organisms in a popu
q^2 = number of aa organisms in a popu
How does the Hardy-Weinburg equation show evidence for natural selection
Calculations for p/q etc. Evolution has occured if tthere are changes to allele frequency
What are the confitions for HW equililibrium
No migration
Population is large
Mating is random
No inbreeding
What is the Hardy-Weinburg principle
The Hardy-Weinberg principle states that if certain conditions are met then the allele frequencies of a gene within a population will not change from one generation to the next
