Name: ______Date: ______Class: ______

MCAS Biology GUIDED WRITING PRACTICE PROBLEMS

Question 23: Ecology (2008)
The diagram below shows a food web for an ecosystem.

a.Identify the producers and the consumers in this food web.
b.In this ecosystem, is more energy available to the field mouse population from eating spiders or
from eating oats? Explain your answer.

Scoring Guide and Sample Student WorkSelect a score point in the table below to view the sample student response.

Score / Description
4 / The response demonstrates a thorough understanding of energy transfer and trophic levels in a food web. The response correctly identifies the producers and consumers from the food web. The response explains why either the oats or spiders provide more available energy to the mouse population.
4
3 / The response demonstrates a general understanding of energy transfer and trophic levels in a food web.
2 / The response demonstrates a limited understanding of energy transfer and trophic levels in a food web.
1 / The response demonstrates a minimal understanding of energy transfer and trophic levels in a food web.
0 / The response is incorrect or contains some correct work that is irrelevant to the skill or concept being measured.
Question 32: Genetics (2008)
Corn snakes show variety in their skin color pattern. While the complete genetics of corn snake color are complex, the most common colors on normal corn snakes—red and black— are each coded by one gene.
For the red gene, the allele for the presence of red pigment (R) is dominant and the allele for the absence of red pigment (r) is recessive. Likewise, for the black gene, the allele for the presence of black pigment (B) is dominant and the allele for the absence of black pigment (b) is recessive.
  1. Draw the Punnett square for the cross of a snake that is homozygous dominant for the red color with a snake that is heterozygous for the red color. What percentage of the offspring is expected to have red pigment in their skin?
  2. Draw the Punnett square for the cross of two snakes that are heterozygous for the black color. What percentage of the offspring are expected to have black pigment in their skin?
  3. The parent snakes in part (b) that are heterozygous for black color are both homozygous recessive for the red gene. Each parent has genotype rr for the red gene. Based on this information, what percentage of their offspring are expected to lack both the red and black pigments in their skin? Explain your reasoning.

Scoring Guide and Sample Student WorkSelect a score point in the table below to view the sample student response.

Score / Description
4 / The response demonstrates a thorough understanding of how to use a Punnett square to determine the probabilities for genotype and phenotype combinations in crosses. The response correctly draws the Punnett squares for the red gene cross and the black gene cross and identifies the correct percent of offspring in each case. The response also identifies and explains the percent of offspring lacking both red and black pigments in the final cross.
4
3 / The response demonstrates a general understanding of how to use a Punnett square to determine the probabilities for genotype and phenotype combinations in crosses.
2 / The response demonstrates a limited understanding of how to use a Punnett square to determine the probabilities for genotype and phenotype combinations in crosses.
1 / The response demonstrates a minimal understanding of how to use a Punnett square to determine the probabilities for genotype and phenotype combinations in crosses.
0 / The response is incorrect or contains some correct work that is irrelevant to the skill or concept being measured.

Question 45: Evolution and Biodiversity (2008)

The graph below relates the number of gray squirrels in a small population to their coat colors.

This squirrel population has been separated from other squirrel populations by a new highway
and several construction sites. The main predators of these squirrels are cats and hawks.

a.Assume that dark gray squirrels are very visible in this new environment. What is likely tohappen to the distribution of coat color in this squirrel population over several generations?Sketch a graph in your Student Answer Booklet to show the predicted distribution, and explainyour answer.

b.Assume that dark gray squirrels are very visible on the ground, and light gray squirrels arevery visible in the trees. Explain what is likely to happen to the distribution of coat color in the squirrel population over several generations. You may sketch a graph in your Student Answer Booklet as part of your explanation.

QUESTION 45 (2008 MCAS) Scoring Guide and Sample Student WorkSelect a score point in the table below to view the sample student response.

Score / Description
4 / The response demonstrates a thorough understanding of natural selection. The response includes an appropriate graph and explains the resulting coat color distribution if dark gray squirrels are very visible in the environment. The response explains what is likely to happen to the coat color distribution if dark gray squirrels are more visible on the ground and light gray squirrels are more visible in trees.
4
3 / The response demonstrates a general understanding of natural selection.
2 / The response demonstrates a limited understanding of natural selection.
1 / The response demonstrates a minimal understanding of natural selection.
0 / The response is incorrect or contains some correct work that is irrelevant to the skill or concept being measured.
Question 44: Biochemistry and Cell Biology (2008)
The diagram below shows a cross section of part of a cell membrane.

a.Describe the basic structure of the cell membrane.
b.Describe two primary functions of the cell membrane.
c.Explain how the structure of the cell membrane allows it to perform the functions
described in part (b).

Scoring Guide and Sample Student WorkSelect a score point in the table below to view the sample student response.

Score / Description
4 / The response demonstrates a thorough understanding of the relationship between the structure and function of the cell membrane. The response correctly describes the basic structure of the cell membrane. The response describes two primary functions of the cell membrane and explains how the structure of the cell membrane allows these functions to be performed.
4
3 / The response demonstrates a general understanding of the relationship between the structure and function of the cell membrane.
2 / The response demonstrates a limited understanding of the relationship between the structure and function of the cell membrane.
1 / The response demonstrates a minimal understanding of the relationship between the structure and function of the cell membrane.
0 / The response is incorrect or contains some correct work that is irrelevant to the skill or concept being measured.

Question 12: Evolution and Biodiversity (2009)

The following section focuses on different lemur species of Madagascar.

Read the information below and use it to answer the four multiple-choice questions and one
open-response question that follow.

Madagascar is an island located off the east coast of Africa, as shown on the map below.

Madagascar has a unique animal community. Lemurs are one of the animal groups that have diversified
extensively on Madagascar. Lemurs are primates, which is an order of mammals that also includes monkeys
and apes. Lemur species vary widely in habitat, diet, size, and color. Lemurs only live on the island of Madagascar. However, fossil evidence shows that lemur ancestors existed on Africa’s mainland. Scientists hypothesize that lemur ancestors reached Madagascar by floating across the Mozambique Channel on matted clumps of vegetation.

Four different lemur species are shown in figures 1–4 below.

The lemurs shown in figures 1–4 all have prominent body features, such as eyes, fingers, legs, tails, and coats.

  1. Choose three of the lemurs in the figures. Using the figures, identify one prominent, visible feature for each of the lemur species you chose. Then describe a likely scenario in which natural selection favored the evolution of this feature. Be sure to discuss a different feature for each lemur.

See the next page for the scoring guide

Question 12 (2009) Scoring Guide and Sample Student WorkSelect a score point in the table below to view the sample student response.

Score / Description
4 / The response demonstrates a thorough understanding of evolution through natural selection. The response correctly identifies a prominent feature for three of the four lemurs and describes a likely scenario in which natural selection favored the evolution of each feature.
4
3 / The response demonstrates a general understanding of evolution through natural selection.
2 / The response demonstrates a limited understanding of evolution through natural selection.
1 / The response demonstrates a minimal understanding of evolution through natural selection.
0 / The response is incorrect or contains some correct work that is irrelevant to the skill or concept being measured.

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