Micro/Macro Evolution Flashcards
In a species of fruit fly, Drosophila subobscura, DNA inversions common to high (northern) latitudes occur less frequently at low latitudes, and vice versa. In nearly all sites where the flies have recently been sampled (a span of three continents) the frequency of low-latitude inversions have crept upward. Flies in sites with a temperature increase of half a degree Celsius have the pattern of inversions that 30 years ago existed in flies 70 miles closer to the equator.
Natural selection: the change was inherited and in response to a change in the environment
Researchers found that Tibetan mothers who are able to store more oxygen in their blood have more offspring that live to maturity. In the low-oxygen group, each woman had on average 2.5 children that died during childhood. In the high-oxygen group, that average was just 0.4. It was also determined that this trait was inherited in a way that suggested the difference was due to a single gene.
Natural selection: The result strongly suggests that the high-oxygen gene confers a reproductive advantage, and is spreading through the population.
Atherosclerosis is principally a disease of the modern age, one produced by modern diets and modern life-styles. There is a community in Italy near Milan whose residents don’t get atherosclerosis because of a fortunate mutation in one of their forebearers. This mutation is particularly interesting because the person who had the original mutation has been identified.
Mutation
The US National Health and Nutrition Examination Survey, published by the National Center for Health Statistics (NCHS) on 27 October, 2004, presents trends in estimates of mean weight, height and body mass index of adults from 1960 to 2002.The main finding of the study is not contested. The weight of the average American is increasing alarmingly: the average for both men and women has increased by 11 kilograms over the past 40 years. But the NCHS also publicized a second conclusion: “Adult men and women are roughly an inch taller than they were in 1960.”
This is not an example of evolution. The changes are due to differences in health, nutrition, pollution, and access to health care, and not changes in allele frequencies. Height and weight generally increase in times of prosperity and decreases when conditions are harsher.
Andrew McAdam, at the University of Alberta, Canada, and colleagues monitored four generations of squirrels in the Yukon, Canada, over 10 years. They found that female squirrels now give birth on average 18 days earlier in the year than their great-grandmothers.
Natural selection. Although environmental cues will influence the breeding season, genetics can at least partiall account for the change (15% genetic basis)
Polydactyly – extra fingers or sometimes toes – is one symptom of Ellis-van Creveld syndrome. The syndrome is commonly found among the Old Order Amish of Pennsylvania. In the Amish, in fact, Ellis-van Creveld syndrome has been traced back to one couple, Samuel King and his wife, who came to the area in 1744. The mutated gene that causes the syndrome was passed along from the Kings and their offspring, and today it is many times more common in the Amish population than in the American population at large.
Genetic drift due to the founder effect. The gene is common in the population now because of a chance event several generations ago when the population was very small.
All of the cattle on Iceland are descended from a small group that were brought to the island more than one thousand years ago. The genetic make-up of the Icelandic cattle is now different from that of their cousins in Norway.
Genetic drift
Natural selection
Because a small group of cattle were introduced to the isolated country of Iceland, this would suggest that genetic drift was the cause of changes in the genetic make-up of the cattle. It is possible that natural selection may have also occured, especially if the environment in Iceland is different from the environment in Norway.
The Panama Canal links the Rio Chagres and Rio Grande rivers. When the Panama canal opened, the once-isolated fish communities of the two rivers were given the chance to intermingle. The Rio Grande has gained five freshwater species that previously lived only in the the Rio Chagres, and three species have spread in the opposite direction.
This is not an example of evolution: Based on the information in the question, we know that new species have been added to the rivers. Evolution is defined as a change in allele frequencies within a population or breeding group. Although the river has more diversity, there is no evidence that the gene pool of each species has changed.
Bacteria have been found that can metabolize short nylon oligomers, breaking the nylon linkages with a couple of related enzymes. Since the bonds involved aren’t found in natural products, the enzymes must have arisen since the time nylon was invented (around the 1940s).
Mutation: The information in the question indicates the appearance of a new gene. No information on fitness is provided
Although phenotypes in the premodern world were more geographically bound than they are today, race is not geographical. What is meant is that people take their genes and their cultural preferences and tendencies with them. One portable tendency is to marry someone similar to ourselves. Sociologists call this tendency homogamy. It is through the practice of homogamy that similar phenotypic traits are replicated by cultural selection.
Non-random mating: homogamy, suggests mating is not random. However, homogamy does not always occur.
In generation after generation, individuals of the fly Drosophila were selectively bred. When flies with a strong tendency to fly toward light (positive phototropism) were used as parents for the next generation, their offspring had a greater tendency to fly toward light.Which mode of selection is this?
Directional selection
In ducks and chickens, eggs of intermediate weight have the highest hatching success. Which mode of selection is this?
Stabilizing selection
Fossil evidence indicates that the average size of black bears in Europe increased with each glacial period of the ice ages. Which mode of selection is this?
Directional selection
In a population of marine snails that live among tan rocks covered with white barnacles, the animals are either white (and thus camouflaged while near the barnacles) or tan (and thus hidden while on bare rock. The snails that are neither white or tan, or that lie against the opposite-colored background, are more often seen and eaten by predatory shorebirds. Which mode of selection is this?
Disruptive selection
Human newborns who are under 5 pounds (2.27 kg) or over 10 pounds (4.54 kg) are less likely to survive than babies weighing between 5 and 10 pounds. Which mode of selection is this?
Stabilizing selection
