Other ways populations change: drift, gene flow and mutation
Grade 9 Science Worksheet - Building Confidence
Circle the best answer.
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Alleles of one gene in a patch of 100 plants (model data)
allele copies allele R 60 allele W 140 all alleles in the gene pool 200 Ari counts the alleles of one gene in a patch of 100 plants. Each plant holds 2 alleles. What is p, the frequency of allele R?
- 0.6: 60 R alleles out of 100 plants
- 0.7: 140 of the 200 alleles are W
- 0.3: 60 of the 200 alleles are R
- 60: the number of R alleles counted
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
- 20: half the number of plants
- 42: 40 plants plus 2 alleles
- 40: one allele for each plant
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?
- 0.35: both alleles have the same frequency
- 0.5: the two alleles split the pool evenly
- 1.35: p + q = 1, so 1 + 0.35
- 0.65: 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
- Chance lost R: no R alleles remained from generation 4
- W was the better allele, so it replaced R
- R stayed at 10 of 20 alleles through generation 5
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 was lost by generation 5, as in the 10-plant run
- R rose each generation, so R was the better allele
- R stayed near 1,000 of 2,000 alleles, with small ups and downs
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?
- Gene pool: every allele copy held by the whole population
- Genotype: the pair of alleles that one plant holds
- Population: the plants of one kind living in one area
- Allele frequency: the share of the copies that are one allele
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 pushes frequencies steadily toward the better allele in any population
- Drift is a chance change in allele frequency, strongest in small populations
- Drift makes new alleles by changing the DNA of a gene
- 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?
- Gene flow: seeds from another meadow brought V
- Genetic drift: chance turned some R alleles into V
- Mutation: a change in a gene's DNA made a new allele
- Natural selection: the meadow needed V, so V appeared
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?
- 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
- Gene flow: alleles moved in from another meadow
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?
- Mutation: a gene changed into a new allele
- Genetic drift: chance changed p inside one meadow
- Gene flow: alleles move between populations
- Bottleneck effect: the population suddenly fell in size