Other ways populations change: drift, gene flow and mutation
Grade 9 Science Worksheet - Building Confidence
Circle the best answer.
Read this first
One meadow and its gene pool (model data)
item number plants in the meadow 40 alleles of the gene in each plant 2 Bo lists the alleles of one gene in a meadow. Each plant holds 2 alleles. How many alleles are in the meadow's gene pool?
- 80: 40 plants × 2 alleles each
- 40: one allele for each plant
- 42: 40 plants plus 2 alleles
- 20: half the number of plants
Allele frequencies in a patch (model data)
allele frequency R (p) 0.35 W (q) ? A patch has two alleles of one gene, R and W. Esme knows p for R. What is q, the frequency of W?
- 0.65: p + q = 1, so 1 − 0.35
- 0.5: the two alleles split the pool evenly
- 1.35: p + q = 1, so 1 + 0.35
- 0.35: both alleles have the same frequency
R alleles in a population of 1,000 plants (2,000 alleles) when no allele helps survival (model data)
generation R alleles of 2,000 0 1,000 1 981 2 998 3 1,019 4 998 5 1,004 Kira reads a model run for a population of 1,000 plants (2,000 alleles). No allele helps survival. Which statement fits?
- R stayed near 1,000 of 2,000 alleles, with small ups and downs
- R was lost by generation 5, as in the 10-plant run
- R rose each generation, so R was the better allele
- R swung widely, since 1,000 plants give chance more room
R alleles in two populations when no allele helps survival (model data)
generation 10 plants (20 alleles): R alleles 1,000 plants (2,000 alleles): R alleles 0 10 1,000 1 14 989 2 17 1,014 3 17 991 Luz reads two model runs that both started with half R alleles. No allele helps survival. Which statement about p, the frequency of R, fits the table?
- p moved more in the 1,000-plant run, since its R count changed by up to 14 alleles
- p rose in both runs, since R was the better allele in both populations
- In the 10-plant run p moved from 0.50 to 0.85; in the other it stayed near 0.50
- p changed by about the same amount in both runs over 3 generations
A card from a notebook (model data)
card what it says card 1 the total of all alleles of one gene, held by all the plants of the group Milo reads a card from a notebook. Which term names what the card describes?
- Allele frequency: the share of the copies that are one allele
- Population: the plants of one kind living in one area
- Gene pool: every allele copy held by the whole population
- Genotype: the pair of alleles that one plant holds
The 2 alleles of one plant as a share of the gene pool (model data)
population alleles share of the gene pool 10 plants 20 1 in 10 1,000 plants 2,000 1 in 1,000 Noah reads about one plant in each population that leaves no seedlings, so its 2 alleles leave the gene pool. Which statement about genetic drift does the table support?
- Drift makes new alleles by changing the DNA of a gene
- Drift is strongest in large populations, which have more alleles to change
- Drift is a chance change in allele frequency, strongest in small populations
- Drift pushes frequencies steadily toward the better allele in any population
Alleles found in one meadow (model data)
generation alleles found 1 R, W 2 R, W 3 R, W, V Pia finds a new allele V in generation 3 of a meadow that no outside seeds have reached. Which process made allele V?
- Mutation: a change in a gene's DNA made a new allele
- Genetic drift: chance turned some R alleles into V
- Natural selection: the meadow needed V, so V appeared
- Gene flow: seeds from another meadow brought V
A meadow before and after a model flood (model data)
when plants before the flood 1,000 after the flood 20 A model flood left a few plants in a meadow. It favored no allele. Ren reads the counts. Which event does the table show?
- Gene flow: alleles moved in from another meadow
- Mutation: a gene changed into a new allele
- Founder effect: a few seeds started a new population
- Bottleneck effect: the population suddenly fell to a few plants
A mainland meadow and a new island population (model data)
place plants mainland meadow 1,000 first plants on the island 5 Wind carried a few seeds from a mainland meadow to an empty island, and they grew. Tala reads the counts. Which event does the table show?
- Founder effect: a few individuals started a new population
- Bottleneck effect: a flood cut a large population
- Gene flow: alleles joined a population already there
- Mutation: a gene changed into a new allele
Two meadows and the seeds carried by wind (model data)
meadow p for R seeds carried in meadow 1 0.8 0 meadow 2 0.2 50 Wind carries seeds from meadow 1 into meadow 2, and the seedlings grow there. Which process moves alleles between the meadows, Zee?
- Gene flow: alleles move between populations
- Mutation: a gene changed into a new allele
- Genetic drift: chance changed p inside one meadow
- Bottleneck effect: the population suddenly fell in size