Other ways populations change: drift, gene flow and mutation
Grade 9 Science Worksheet - Building Confidence
Circle the best answer.
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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?
- 40: one allele for each plant
- 80: 40 plants × 2 alleles each
- 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
- 0.35: both alleles have the same frequency
- 0.5: the two alleles split the pool evenly
- 1.35: p + q = 1, so 1 + 0.35
R alleles in a population of 10 plants (20 alleles) when no allele helps survival (model data)
generation R alleles of 20 0 10 1 9 2 6 3 3 4 0 5 0 Jun reads a model run for a population of 10 plants. No allele helps survival. What happened to allele R?
- R became fixed: 20 of 20 alleles were R from generation 4
- W was the better allele, so it replaced R
- R stayed at 10 of 20 alleles through generation 5
- Chance lost R: no R alleles remained from generation 4
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 swung widely, since 1,000 plants give chance more room
- R rose each generation, so R was the better allele
- 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 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 changed by about the same amount in both runs over 3 generations
- In the 10-plant run p moved from 0.50 to 0.85; in the other it stayed near 0.50
- p rose in both runs, since R was the better allele in both populations
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 pushes frequencies steadily toward the better allele in any population
- Drift is a chance change in allele frequency, strongest in small populations
- Drift is strongest in large populations, which have more alleles to change
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?
- Genetic drift: chance turned some R alleles into V
- Gene flow: seeds from another meadow brought V
- Natural selection: the meadow needed V, so V appeared
- Mutation: a change in a gene's DNA made a new allele
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
- Bottleneck effect: the population suddenly fell to a few plants
- Mutation: a gene changed into a new allele
- Founder effect: a few seeds started a new population
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?
- Gene flow: alleles joined a population already there
- Founder effect: a few individuals started a new population
- Mutation: a gene changed into a new allele
- Bottleneck effect: a flood cut a large population
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
- Bottleneck effect: the population suddenly fell in size
- Genetic drift: chance changed p inside one meadow