18. populations and evolution

Question 1

What 5 assumptions are made when using the hardy-weinberg principle

Answer 1

• no mutations
• population is isolated, there is no flow of alleles into or out of population
• no selection
• population is large
• mating within the population is random

Question 2

Write down the hardy-weinberg equation.

Answer 2

p+q=1.0
p2 + 2pq + q2 = 1
(p2 and q2 = squared)

Question 3

What does the Hardy-Weinberg principle calculate?

Answer 3

Allele frequencies in a particular gene population,
Proportions of dom and rec of any gene remains the same

Question 4

Gene Pool

Answer 4

All alleles and genes of all individuals in a population.

Question 5

Allele Frequency

Answer 5

Number of times an alleles occurs in gene pool.

Question 6

What three genetic factors affect variation?

Answer 6

• mutation
• meiosis
• random fertilisation of gametes

Question 7

Why does height have a normal distribution curve?

Answer 7

• polygenes (controlled by many genes)
• environmental factors (eg diet)

Question 8

Selected Pressures.

Answer 8

Environmental factors that limit the population of a species

Question 9

What three things does natural selection depend on?

Answer 9

• There is more offspring than the environment can support
• There is genetic variety within all populations
• phenotypes to select against

Question 10

Explain the importance of selective pressures on evolution

Answer 10

Some phenotypes have selective advantages, more likely to reproduce and pass on desired alleles.
Results in a change in allele frequency (evolution)

Question 11

What are the three types of selection?

Answer 11

• stabilising
• directional
• disruptive

Question 12

Describe disruptive selection.

Answer 12

Individuals with EITHER extreme allele is more likely to survive = more frequent
‘middle’ allele becomes less frequent.

Question 13

Explain speciation.

Answer 13

Process which results in the creation of new species, occurs when species become reproductively isolated. (cannot breed)

Differences in their gene pools make them unable to make fertile offspring

Question 14

What are the two types of speciation?

Answer 14

• allopatric (geographic)
• sympatric (changes in reproductive mechanisms)

Question 15

Explain two ways sympatric speciation can occur

Answer 15

• random mutation impacts courtship ritual of some individuals
• or fertile at different times of the year
• both result in no gene flow between two groups
• each populations accumulate different mutations until they cannot interbreed

Question 16

Genetic drift.

Answer 16

Change in allele frequency within a population between generations. = evolution

Question 17

how does the size of population have on the impact of genetic drift?

Answer 17

The smaller the population the bigger the impact - allele frequency changes proportionally happen more often.

Question 18

name all the components of the hardy weinberg equation.

Answer 18

p= dominant allele
q= recessive allele
p squared = homozygous dominant
2pq = heterozygous genotype
q squared = homozygous recessive