Science Assessment ~ Topics ~ Common Ancestry ~ Item CA009004 ~ Student Performance

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If the DNA of lizards and dogs is more similar than the DNA of lizards and toads, what is a reasonable conclusion about the common ancestors of these three groups?

Lizards and dogs have a common ancestor, but lizards and toads do not.
Lizards and dogs have a more recent common ancestor than lizards and toads.
Lizards and toads have a more recent common ancestor than lizards and dogs.
Similarities in DNA cannot provide information about the common ancestors of lizards, dogs, and toads because lizards, dogs, and toads do not have a common ancestor.

Pre-Test

Distribution of responses (prior to studying evolution in high school)
Answer Choice		Overall	Grades		Gender		Primary Language
		n = 558	6–8 n = 25	9–12 n = 498	Male n = 243	Female n = 274	English n = 502	Other n = 19
A.	Lizards and dogs have a common ancestor, but lizards and toads do not.	18%	24%	18%	21%	16%	19%	11%
B.	Lizards and dogs have a more recent common ancestor than lizards and toads.	45%	40%	45%	42%	48%	45%	37%
C.	Lizards and toads have a more recent common ancestor than lizards and dogs.	19%	24%	18%	21%	16%	18%	26%
D.	Similarities in DNA cannot provide information about the common ancestors of lizards, dogs, and toads because lizards, dogs, and toads do not have a common ancestor.	19%	12%	18%	16%	20%	18%	26%

Post-Test (Control)

Distribution of responses (following typical high school instruction on evolution)
Answer Choice		Overall	Grades		Gender		Primary Language
		n = 294	6–8 n = 23	9–12 n = 247	Male n = 109	Female n = 171	English n = 264	Other n = 9
A.	Lizards and dogs have a common ancestor, but lizards and toads do not.	14%	39%	12%	17%	12%	15%	11%
B.	Lizards and dogs have a more recent common ancestor than lizards and toads.	62%	39%	64%	61%	63%	61%	67%
C.	Lizards and toads have a more recent common ancestor than lizards and dogs.	14%	13%	14%	14%	16%	14%	22%
D.	Similarities in DNA cannot provide information about the common ancestors of lizards, dogs, and toads because lizards, dogs, and toads do not have a common ancestor.	9%	9%	10%	9%	9%	10%	0%

Post-Test (Treatment)

Distribution of responses (following completion of an evolution curriculum module)
Answer Choice		Overall	Grades		Gender		Primary Language
		n = 281	6–8 n = 3	9–12 n = 257	Male n = 132	Female n = 140	English n = 254	Other n = 11
A.	Lizards and dogs have a common ancestor, but lizards and toads do not.	8%	0%	9%	12%	5%	9%	0%
B.	Lizards and dogs have a more recent common ancestor than lizards and toads.	73%	100%	74%	68%	79%	75%	64%
C.	Lizards and toads have a more recent common ancestor than lizards and dogs.	12%	0%	12%	13%	9%	11%	18%
D.	Similarities in DNA cannot provide information about the common ancestors of lizards, dogs, and toads because lizards, dogs, and toads do not have a common ancestor.	7%	0%	6%	7%	7%	5%	18%