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MCAS Evolution

Feb 2016 MCAS.  Scientists often compare fossils of extinct organisms with living organisms to help determine evolutionary relationships. What is the primary information that scientists use when comparing fossils with living organisms?

A. the types of minerals that formed the fossils
B. the size of the rocks that contained the fossils
C. the cause of death for the fossilized organisms
D. the physical characteristics of the fossilized organisms


Feb 2016 MCAS .

The pictures below show the shells of some species of land snails found on a Pacific island. Each species was found on a different hill on the island. Based on the snails’ shell shapes, scientists made hypotheses about the evolutionary relationships among the snails. Which of the following would be the best characteristic to compare in order to test these hypotheses?

Snail shells 16

A. the size of the snails
B. the diet of the snails
C. the DNA of the snails
D. the average age of the snails


Scientists hypothesized that several species of frogs called tiger frogs evolved from a recent common ancestor. The hypothesis was based on fossil evidence and on physical similarities among living species.

Which of the following provides the best additional support for the scientists’ hypothesis?

A. Tiger frogs have longer life spans than other frog species.
B. Tiger frogs have the same diet and all use enzymes to digest food.
C. Tiger frogs live near each other and are all preyed upon by the same predator species.
D. Tiger frogs have similarities in their mitochondrial DNA that are not shared by other frog species.


Spring 2017

Some populations of Atlantic tomcod fish have an allele that makes the fish resistant to toxic pollutants called PCBs. Tomcod populations in several rivers were analyzed for the presence of this allele. Each river had varying levels of PCB pollution. Which of the following results would best support the conclusion that natural selection is influencing the presence of this allele in the tomcod populations?

A. All of the tomcod in each of the rivers have this allele.

B. The percentage of tomcod with this allele remains the same from year to year in each river.

C. The rivers with high PCB levels have larger percentages of tomcod with this allele than the rivers without PCBs.

D. Eggs from tomcod without this allele can hatch in rivers with or without PCBs, and eggs from tomcod with this allele can only hatch in rivers without PCBs.


Spring 2017.

A researcher observed army ants, which form colonies with one queen ant and many worker ants. The researcher observed worker ants moving from place to place to hunt and collect a variety of food for the colony. The queen ant was observed mating with a male ant from another ant colony. The queen produced many eggs after this mating. Which of the following could help increase the genetic diversity in the colony of army ants?

A. the queen ant mating with the ant from a different colony
B. the worker ants collecting the food for the colony to eat
C. the worker ants moving from place to place
D. the queen ant eating a variety of food


Scientists discovered a 375-million-year old fossil in Canada. The diagram below shows the top and side views of the fossil.

Transitional form fossil amphibian
Which observation would best support the hypothesis that this organism was
a transitional form between amphibians and fish?



A. The fossil has a long body, which both modern amphibians and modern fish have.
B. The fossil is larger than most modern amphibians, but smaller than most ancient fish.
C. The fossil has some body structures that are similar to amphibians and some body structures that are similar to fish.
D. The fossil was discovered near a lake, which shows that the organism
needed water to reproduce, as do amphibians and fish.


Some plants in an area produce a toxin that protects them from being eaten by a variety of insect species. The toxin decreases reproductive rates in insects. Because of a genetic mutation, some fruit flies can detect the plant toxin and therefore avoid eating the plant.

a. Describe how the number of fruit flies in the population that can detect the toxin will most likely change over the next 25 years.

b. According to the mechanism of natural selection, explain how the change you described in part (a) will occur.

c. Based on the changes in the fruit fly population, describe what will most likely happen to the plants’ production of the toxin. Explain your answer.



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