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Massachusetts Comprehensive Assessment System

2016, High School Biology

  Question 45: Open-Response  
The western snowy plover is a small bird that makes its nest in the sand on ocean and river shores. The snowy plover’s breeding season is from March to September. A plover typically lays three eggs each year. If disturbed, it will often abandon its nest. A snowy plover and its nest are shown below.
The diagram shows a small bird standing next to a nest containing three eggs in the sand.
  1. Compare the birth rate (number of eggs hatched) to the death rate in a population of snowy plovers that is increasing in size.
In an initial population of 100 snowy plovers, there were 30 births and 20 deaths in one year.
  1. Based only on the birth and death rates, identify the expected size of the snowy plover population at the end of the year.
At the end of the year, there were actually 80 snowy plovers in the population.
  1. Assuming there were no additional births or deaths, explain why the actual population size differed from the expected population size.
Current efforts to conserve plover populations include building wire fences around their nests and making certain beaches off-limits to people during plover breeding season.
  1. Explain why making certain beaches off-limits during plover breeding season is a more effective conservation method than building fences around plover nests.

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

ScoreDescription
4 The response demonstrates a thorough understanding of how birth, death, immigration, and emigration influence population size and of how population sizes can be affected by human activity. The response correctly compares the birth rate and death rate in a population of snowy plovers that is increasing in size, correctly identifies the expected size of the population, and clearly explains why the actual population size differed. The response also clearly explains why making beaches off-limits during plover breeding season is a more effective conservation method than building fences around nests.
4
3 The response demonstrates a general understanding of how birth, death, immigration and emigration influence population size and of how population sizes can be affected by human activity.
2 The response demonstrates a limited understanding of how birth, death, immigration and emigration influence population size and of how population sizes can be affected by human activity.
1 The response demonstrates a minimal understanding of how birth, death, immigration and emigration influence population size and of how population sizes can be affected by human activity.
0 The response is incorrect or contains some correct work that is irrelevant to the skill or concept being measured.

Note: There are 2 sample student responses for Score Point 4.

High School Biology

Question 12: Anatomy and Physiology
Question 23: Evolution and Biodiversity
Question 32: Biochemistry and Cell Biology
Question 44: Genetics
Question 45: Ecology

Return to the MCAS 2016 Student Work Directory



Last Updated: September 23, 2003
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