Key Idea: Similarities and differences in inherited characteristics of organisms alive today or in the past can be used to infer the relatedness of any two species, changes in species over time, and lines of evolutionary descent.

Students are expected to know that:

  1. The fact that organisms retain some of the inherited characteristics of their ancestors from many generations ago makes it possible for scientists to identify both recent and past ancestors of those organisms.
  2. Inherited characteristics (both internal and external) of species alive today can be compared to determine how similar the species are. Organisms with more similarities are usually more closely related to each other than organisms with fewer similarities, i.e., organisms that have more similarities tend to have a more recent common ancestor than those with fewer similarities.
  3. Inherited characteristics (both internal and external) of species alive today can be compared to the characteristics of species that lived in the past to determine how similar they are. Organisms with more similarities are usually more closely related to each other than organisms with fewer similarities, i.e., organisms that have more similarities tend to have a more recent common ancestor than those with fewer similarities.
  4. Some structures which do not seem similar in gross structure and function (e.g. the hand of a human and the front flipper of a whale) may after closer analysis of the detailed anatomy be shown to have the same origin.
  5. The relative ages of fossils can be used to help infer lines of evolutionary descent. Relative ages of fossils are determined by their relative positions in the earth's rock layers.
  6. Evidence for common ancestry across a wide variety of species provides support for the idea that all multi-cellular organisms (including humans) share a common ancestor. Evidence also indicates that life began as single-celled organisms and that complex multi-cellular organisms evolved from them.

Boundaries:

  1. Students are not expected to know about convergent evolution.
  2. Students are not expected to know about analogy and homology.
  3. Students are not expected to know about Archae bacteria and the possible multiple origins of life.
  4. Students are not expected to know methods of dating.
  5. Students are not expected to know the approximate date of the origin of life or when any particular species or type of organism originated.
Frequency of selecting a misconception

Misconception
ID Number

Student Misconception

Grades
6–8

Grades
9–12

ENM041

Species that are similar can share a common ancestor, but species that have no apparent, obvious, or superficial similarities cannot share a common ancestor (Poling & Evans, 2004; Stern & Hagay, 2005).

47%

44%

ENM039

Plants and animals cannot share a common ancestor (Bizzo, 1994; Ha & Cha, 2008).

40%

33%

ENM038

Humans do not share a common ancestor with other living organisms (Ha & Cha, 2008; Stern & Hagay, 2005).

35%

25%

ENM054

Members of different species do not share a common ancestor (Poling & Evans, 2004; Shtulman, 2006).

24%

21%

Frequency of selecting a misconception was calculated by dividing the total number of times a misconception was chosen by the number of times it could have been chosen, averaged over the number of students answering the questions within this particular idea.