An organism which has not changed a lot over time

An organism that has been widely studied

An organism that is difficult to study

An organism that doesn’t have much to teach scientists

Fish in the different lakes were different from one another when they arrived there after the last ice age.

The water temperatures affected how the fish develop as embryos

Some lakes had more predators, and different traits were naturally selected in each lake

In some lakes, spines caused fish to swim slower than in other lakes.

genetic drift

natural selection

reproductive isolation

survival of the fittest

The graph indicates that Bear Paw Lake has more fish than Frog Lake.

The data suggest that fish in Bear Paw Lake are bigger than those in Frog Lake.

The graph suggests that all fish in Bear Paw Lake lack pelvic spines and all fish in Frog Lake have pelvic spines.

The data suggest that the fish in Frog Lake vary widely in pelvic structures.

Frog Lake

Bear Paw Lake

Layer 1

Layer 2

Layer 3

Layer 4

The frequencies of reduced and complete pelvic phenotypes fluctuate from layer to layer, but overall, there is no trend in gain or loss of either trait in the population.

Initially, the stickleback population in the lake consisted mostly of fish with pelvic spines, but over 15,000 years the population changed to fish without pelvic spines.

Initially, very few fossil stickleback sampled had the complete pelvic phenotype, but in the following 15,000 years, the frequency of this phenotype in the population increased significantly.

The frequencies of absent and reduced pelvic phenotypes are roughly equal throughout the 15,000-year time span studied because the lake became flooded at one point, which allowed trout to enter the lake from other areas.

Over many generations, populations of fish changed in many different ways, including in their skeletons.

They acquired new characteristics by mating with fish that lived in these lakes.

Since the new environments were so similar to their old environments, their traits changed.

The new environments caused individual fish to change within their lifetime.

True

False

Legs

Arms

Tails

Wings

In sea water, pelvic spines help fish swim faster, but not in fresh water.

The pelvic spines are homologous to legs in four-legged animals. Because fish don't need hind limbs to walk, many populations of fish evolved to lack pelvic spines.

In lakes where there are no predatory fish, there is no advantage to having pelvic spines.

Pelvic spines are thought to attract mates for reproduction in the sea but not in lakes.

To have a larger number of specimens to score, increasing the accuracy of results.

To compare the trait in stickleback populations living in two potentially different environments.

Frog Lake and Bear Paw Lake are two lakes with very similar stickleback populations.

One lake represents the control population and the other population is the one we can compare to the control.

In each generation, some individuals may, just by chance, have more offspring than other individuals and their traits will become more common in that population.

More advantageous traits in a particular environment allow individuals with those traits to have more offspring; as a result their heritable traits become more common in succeeding generations of the population.

Mutations occur at random in a population causing populations to change over time as those mutations are inherited from one generation to the next.

Only traits that are advantageous in a particular environment are preserved in the fossil record.

It is the gene identified to be involved in the formation of the pelvic spines in stickleback fish; this gene is not found in any other organism.

It is the gene involved in the formation of pelvic spines in fossil stickleback populations, but scientists don't yet know whether it is involved in the formation of pelvic spines in modern fish populations.

It is the gene that regulates the formation of hind limbs in mice and other four-legged animals; scientists don't yet know whether stickleback fish have a Pitx1 gene.

It is the gene identified to be involved in the formation of the pelvic spines in stickleback fish, as well as hind limb development in other vertebrates, such as the mouse.

If in a population, pelvic vestiges are larger on either the left or right side in most fish, that suggests that the Pitx1 gene is involved in this phenotype.

Any type of asymmetry in the body indicates that the Pitx1 gene is involved.

If the pelvic vestiges are larger on the left side in most stickleback in a population, the Pitx1 gene is probably involved in pelvic reduction.

If the pelvic vestiges are larger on the right side in most stickleback in a population, that's evidence that the Pitx1 gene in stickleback fish is the same as the Pitx1 gene in mice.

Random sampling increases the probability that the specimens selected for the research study are representative of the population as a whole.

Random sampling ensures that every fish in the population is sampled.

Random sampling ensures that the fish that are selected for the research study are most like one another.

Random sampling is the only way to collect fish when using traps