Populations (A Level only) (AQA A Level Biology): Flashcards
Exam code: 7402
1/260Still learning
Know0
- FrontPopulations
Define the term species
Was this flashcard helpful?
Cards in this collection (26)
Define the term species
A group of similar organisms that can reproduce to give fertile offspring
Define the term population
A group of organisms of the same species occupying a particular space at a particular time that can potentially interbreed
What do all organisms of the same species have in common regarding their chromosomes?
They have the same number of chromosomes in their cells
How many chromosomes are found in the cells of a human?
Even if they can mate, the offspring are often infertile.
If the parents have different chromosome numbers, the chromosomes cannot pair up during meiosis, so functional gametes cannot form.
Explain why two organisms from different species cannot produce fertile offspring
They have different numbers of chromosomes
The chromosomes cannot pair up properly during meiosis
This means the offspring cannot produce gametes and is therefore infertile
True or False?
A horse and a donkey can produce fertile offspring
False.
Their offspring has an odd number of chromosomes (63), so the chromosomes cannot pair up in meiosis and the offspring is infertile
Members of a species do not live alone; instead, they live in .
Members of a species do not live alone; instead, they live in populations.
The key test of whether two organisms belong to the same species is whether they can produce offspring.
The key test of whether two organisms belong to the same species is whether they can produce fertile offspring.
Define the term gene pool
The sum of all the alleles of the genes of a population (of a single species) at a particular time
What is meant by allele frequency?
How often a particular allele occurs in the gene pool of a population
Name a process that can cause allele frequencies to change over time
Natural selection
A gene pool is the collection of genes within an population at a particular time.
A gene pool is the collection of genes within an interbreeding population at a particular time.
When the allele frequencies within a species population change sufficiently over time, this can lead to or the formation of a new species.
When the allele frequencies within a species population change sufficiently over time, this can lead to evolution or the formation of a new species.
What is meant by phenotype frequency?
The number of individuals in a population showing a particular observable trait
State the formula used to calculate phenotype frequency (as a percentage)
Phenotype frequency = (total individuals with phenotype / total individuals in population) x 100
In a population of 9 pea plants, 7 have purple flowers. Calculate the phenotype frequency of purple flowers as a percentage
Phenotype frequency = (7 / 9) x 100
= 78%
State the Hardy-Weinberg principle
Allele frequencies in a population will remain constant from one generation to the next, provided that certain conditions are met
State the conditions that must be met for the Hardy-Weinberg principle to apply
There is no mutation
There is no natural selection
The population is large
Mating is random
There is no migration (no gene flow)
In the Hardy-Weinberg equations, what do p and q represent?
p = the frequency of the dominant allele
q = the frequency of the recessive allele
State the Hardy-Weinberg equation that relates the frequencies of the two alleles of a gene
p + q = 1
State the Hardy-Weinberg equation used to calculate genotype frequencies
p2 + 2pq + q2 = 1
In the equation p2 + 2pq + q2 = 1, what does each term represent?
p^2 = frequency of the homozygous dominant genotype
2pq = frequency of the heterozygous genotype
q^2 = frequency of the homozygous recessive genotype
True or False?
The Hardy-Weinberg principle assumes that allele frequencies change between generations
False.
The principle assumes there is no change in allele frequencies between generations (i.e. genetic equilibrium)
In a population of birds, 10% show the recessive phenotype of white feathers. Calculate the frequency of the recessive allele (q)
q^2 = 0.10
q = square root of 0.10 = 0.32
If the frequency of the recessive allele q = 0.32, calculate the frequency of the dominant allele p
p = 1 - q
p = 1 - 0.32 = 0.68
In a Hardy-Weinberg calculation, you should always begin by identifying the frequency of the recessive phenotype, which is represented by .
In a Hardy-Weinberg calculation, you should always begin by identifying the frequency of the recessive phenotype, which is represented by q^2.
Sign up to unlock flashcards
or