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 SP009004: The best evidence that organisms from two populations (Cichlid fish) are from the same species is the presence of allele mixing in their offspring.
Cichlids are a group of fish that live in freshwater lakes. Scientists wanted to determine whether two populations of cichlids that live at different depths of a lake interbreed. They knew that cichlids must be able to see potential mates in order to reproduce with them. They also knew that cichlids with particular genotypes see better at different water depths. Information about three different genotypes is summarized in the table below:
|
Genotype |
Ability to see potential mates in deep water | Ability to see potential mates in shallow water |
|---|---|---|
| LL | Excellent | Poor |
| HH | Poor | Excellent |
| LH | Moderate | Moderate |
If scientists determined the genotypes of a representative sample of fish from both the deep and shallow water populations, what would provide the best evidence that some of the individuals in the deep and shallow water populations are reproducing with each other?
- All individuals in both deep and shallow water populations have just the LL genotype.
- Individuals with the LL, HH, and LH genotypes are present in both the deep and shallow water populations.
- Only the LL genotype is present in the deep water population and only the HH genotype is present in the shallow water population.
- Not enough information is provided.
Pre-Test
Answer Choice |
Overall |
Grades |
Gender |
Primary Language |
||||
|---|---|---|---|---|---|---|---|---|
| n = 572 |
6–8 n = 18 |
9–12 n = 502 |
Male n = 245 |
Female n = 283 |
English n = 511 |
Other n = 18 |
||
| A. | All individuals in both deep and shallow water populations have just the LL genotype. | 4% | 11% | 4% | 5% | 4% | 4% | 6% |
| B. | Individuals with the LL, HH, and LH genotypes are present in both the deep and shallow water populations. | 43% | 39% | 43% | 40% | 46% | 43% | 39% |
| C. | Only the LL genotype is present in the deep water population and only the HH genotype is present in the shallow water population. | 34% | 28% | 36% | 36% | 33% | 35% | 39% |
| D. | Not enough information is provided. | 18% | 22% | 17% | 19% | 18% | 18% | 17% |
Post-Test (Control)
Answer Choice |
Overall |
Grades |
Gender |
Primary Language |
||||
|---|---|---|---|---|---|---|---|---|
| n = 274 |
6–8 n = 14 |
9–12 n = 230 |
Male n = 119 |
Female n = 130 |
English n = 237 |
Other n = 9 |
||
| A. | All individuals in both deep and shallow water populations have just the LL genotype. | 3% | 0% | 3% | 3% | 2% | 3% | 0% |
| B. | Individuals with the LL, HH, and LH genotypes are present in both the deep and shallow water populations. | 45% | 57% | 44% | 48% | 44% | 44% | 56% |
| C. | Only the LL genotype is present in the deep water population and only the HH genotype is present in the shallow water population. | 35% | 29% | 34% | 29% | 37% | 34% | 44% |
| D. | Not enough information is provided. | 18% | 14% | 19% | 20% | 17% | 19% | 0% |
Post-Test (Treatment)
Answer Choice |
Overall |
Grades |
Gender |
Primary Language |
||||
|---|---|---|---|---|---|---|---|---|
| n = 278 |
6–8 n = 4 |
9–12 n = 248 |
Male n = 130 |
Female n = 131 |
English n = 251 |
Other n = 5 |
||
| A. | All individuals in both deep and shallow water populations have just the LL genotype. | 1% | 0% | 2% | 2% | 1% | 2% | 0% |
| B. | Individuals with the LL, HH, and LH genotypes are present in both the deep and shallow water populations. | 51% | 25% | 52% | 55% | 47% | 53% | 40% |
| C. | Only the LL genotype is present in the deep water population and only the HH genotype is present in the shallow water population. | 31% | 25% | 31% | 30% | 31% | 31% | 20% |
| D. | Not enough information is provided. | 17% | 50% | 15% | 12% | 21% | 15% | 40% |