Evolution
Evolution and Natural Selection
New species can arise when barriers to reproduction within a population lead to two populations that over time e…
Item SP008002: The best evidence that two organisms (red monkeyflower plants and pink monkeyflower plants) do not reproduce with each other is the absence of allele mixing in their offspring.
There are two kinds of monkeyflower plants in a field: one has pink flowers and one has red flowers. Scientists wondered if the pink and red monkeyflower plants were different species. They knew that a particular genotype in the monkeyflower plants determines what each plant reproduces with. Descriptions of the three possible genotypes are shown below:
| Monkeyflower Genotype | |
| CC | Reproduces with red monkeyflower plants |
| LL | Reproduces with pink monkeyflower plants |
| LC | Reproduces with pink monkeyflower plants and red monkeyflower plants |
If scientists determined the genotypes of a representative sample of monkeyflower plants in the field, what would provide the best evidence that the red monkeyflower plants and the pink monkeyflower plants do not reproduce with each other?
- All of the plants in the sample have the LC genotype.
- All of the plants in the sample have either the LL or CC genotypes.
- Equal numbers of plants in the sample have the LL genotype, LC, and CC genotypes.
- Most of the plants in the sample have the LC genotype, a few have the LL genotype, and a few have the CC genotype.
The scenario presented here is based on an actual scientific study (Bradshaw and Schemske, 2003); however, it has been simplified for testing purposes.
Pre-Test
Answer Choice |
Overall |
Grades |
Gender |
Primary Language |
||||
|---|---|---|---|---|---|---|---|---|
| n = 580 |
6–8 n = 25 |
9–12 n = 514 |
Male n = 254 |
Female n = 286 |
English n = 526 |
Other n = 13 |
||
| A. | All of the plants in the sample have the LC genotype. | 9% | 20% | 9% | 9% | 9% | 10% | 8% |
| B. | All of the plants in the sample have either the LL or CC genotypes. | 45% | 40% | 45% | 48% | 44% | 46% | 31% |
| C. | Equal numbers of plants in the sample have the LL genotype, LC, and CC genotypes. | 23% | 16% | 24% | 24% | 22% | 23% | 31% |
| D. | Most of the plants in the sample have the LC genotype, a few have the LL genotype, and a few have the CC genotype. | 22% | 24% | 22% | 19% | 24% | 21% | 31% |
Post-Test (Control)
Answer Choice |
Overall |
Grades |
Gender |
Primary Language |
||||
|---|---|---|---|---|---|---|---|---|
| n = 255 |
6–8 n = 15 |
9–12 n = 195 |
Male n = 97 |
Female n = 119 |
English n = 205 |
Other n = 6 |
||
| A. | All of the plants in the sample have the LC genotype. | 7% | 7% | 8% | 7% | 8% | 7% | 0% |
| B. | All of the plants in the sample have either the LL or CC genotypes. | 50% | 33% | 51% | 54% | 47% | 50% | 33% |
| C. | Equal numbers of plants in the sample have the LL genotype, LC, and CC genotypes. | 19% | 13% | 19% | 16% | 18% | 18% | 17% |
| D. | Most of the plants in the sample have the LC genotype, a few have the LL genotype, and a few have the CC genotype. | 24% | 47% | 23% | 23% | 27% | 25% | 50% |
Post-Test (Treatment)
Answer Choice |
Overall |
Grades |
Gender |
Primary Language |
||||
|---|---|---|---|---|---|---|---|---|
| n = 301 |
6–8 n = 8 |
9–12 n = 274 |
Male n = 134 |
Female n = 150 |
English n = 274 |
Other n = 9 |
||
| A. | All of the plants in the sample have the LC genotype. | 4% | 0% | 4% | 6% | 2% | 4% | 0% |
| B. | All of the plants in the sample have either the LL or CC genotypes. | 55% | 75% | 55% | 47% | 63% | 55% | 78% |
| C. | Equal numbers of plants in the sample have the LL genotype, LC, and CC genotypes. | 16% | 13% | 16% | 19% | 11% | 16% | 11% |
| D. | Most of the plants in the sample have the LC genotype, a few have the LL genotype, and a few have the CC genotype. | 25% | 13% | 25% | 28% | 24% | 26% | 11% |