Key Idea: When inherited traits are favorable to individual organisms, the proportion of individuals in a population that have those traits will tend to increase over successive generations.

Students are expected to know that:

  1. There is variation in the inherited traits of organisms of the same species, including traits that affect their ability to find food, avoid predators, and attract mates.
  2. Some inherited traits (e.g. bacterial resistance to antibiotics, skin pigmentation in some organisms) may give individuals of a species an advantage in surviving and reproducing in their environment compared to other individuals of the same species (e.g. increased ability to find food or nesting sites, avoid predators, attract mates, resist diseases). Conversely, the individuals that do not have advantageous trait(s) are more likely to be unable to survive and reproduce.
  3. An organism’s survival influences its reproductive success. Usually, the longer an organism lives (during its reproductive years), the more chances it has to reproduce; therefore traits that improve chances of survival (such as finding food or avoiding predators) also increase chances of success in reproduction.
  4. Changes in environmental conditions (such as the appearance of a new predator, a slight change in temperature, or changes due to the eruption of a volcano) can change which traits are more advantageous (or less detrimental) in the new environment.
  5. Because more of the individuals with favorable inherited traits survive and reproduce than those that do not have them, and because the favorable traits are passed on to the offspring, the proportion of individuals with the favorable inherited traits increases in each subsequent generation. This process is called natural selection.
  6. There is no guarantee that any members of a population will be able to survive and reproduce in a changed environment. Sometimes changes in environmental conditions may cause an entire population of organisms to die, or even an entire species to become extinct.
  7. The process of natural selection does not lead to changes in the characteristics of individual organisms. It only changes the characteristics of populations (i.e. the proportion of individuals in the population having certain inherited traits) over time.
  8. After natural selection has operated on many successive generations of a population, the descendants can be very different from their original ancestors.
  9. Even though organisms can be very different in both appearance and behavior from their ancestors of many generations ago, they retain some of the inherited traits of those early ancestors.

Boundaries:

  1. Students are not expected to know the many ways speciation can occur in a population.
  2. Students are not expected to know the origin of variation among individuals in a population (i.e. how genetic mutations happen).
Percent of students answering correctly (click on the item ID number to view the item and additional data)
Item ID
Number
Knowledge Being Assessed Grades
6–8
Grades
9–12
Select This Item for My Item Bank

EN034003

Some organisms survive and others die as the environment changes; this changes the proportion of organisms with certain traits in that population.

100%

77%

EN043002

Over thousands of years, there will be changes to the environment that could lead to changes in the traits of species.

67%

75%

EN033002

If members of a species were moved to a new environment, many generations later their offspring would have both differences and similarities compared to the original population, because different traits are favorable in different environments.

60%

68%

EN029002

In a population of light and dark moths, if the number of dark trees for the moths to hide in suddenly increases, the number of dark moths will increase in each generation because more dark moths will survive and reproduce than light moths.

57%

68%

EN023001

When a new predator is introduced into a population of lizards, the individual lizards with the traits that best help them avoid the predator are more likely to survive and reproduce than the others.

100%

58%

EN041002

Individual members of a species can vary in their ability to find food and to avoid predators.

55%

66%

EN039002

Individual members of a species can vary in their ability to find food and to reproduce.

54%

58%

EN028002

If only large seeds are available, only the birds with large enough beaks will get enough food to survive and reproduce, and they will pass the trait of large beaks to the next generation.

51%

60%

EN034002

Some organisms survive and others die as the environment changes; this changes the percent of organisms with certain traits in that population.

41%

54%

EN045002

Individuals of the same species may differ in their inherited traits, and these differences may affect their relative success in survival and reproduction.

37%

46%

EN038002

Traits must be inherited from one generation to the next in order for natural selection to occur.

35%

45%

EN021002

When a change occurs in the environment, the individuals that have traits that are better suited for the changed environment would be more likely to survive and reproduce.

29%

53%

EN022002

If the type of seed available to a population of birds changes, the individual birds with the beak best equipped for eating the new type of seed are more likely to survive and reproduce than the others.

32%

45%

EN026002

A population can differ from its ancestors because an environmental change can affect which inherited traits are most helpful and, therefore, which individuals are more likely to survive and reproduce.

29%

44%

EN038003

Traits must be inherited from one generation to the next in order for natural selection to occur.

35%

33%

EN030002

Bacteria become resistant to antibiotics when a few individual resistant bacteria survive and reproduce, passing their resistance on to the next generation.

21%

35%

EN032002

Species can change over generations because individuals with traits that are helpful in the current environment are more likely to survive and pass those traits on to their offspring.

20%

29%

Frequency of selecting a misconception

Misconception
ID Number

Student Misconception

Grades
6–8

Grades
9–12

ENM031

Individual organisms can deliberately develop new heritable traits because they need them for survival (Bishop & Anderson 1990; Passmore et al., 2002; Stern & Roseman, 2004).

34%

28%

ENM046

Sudden environmental change is required for evolution to occur (Nehm & Reilly, 2007).

32%

30%

ENM037

Changes in a population occur through a gradual change in all members of a population, not from the survival of a few individuals that preferentially reproduce (Brumby, 1979; Bishop & Anderson, 1990; Anderson et al., 2002; Stern & Roseman, 2004).

26%

28%

ENM047

Evolution happens when individual organisms acclimate or "get used to" new conditions gradually (Bishop & Anderson, 1990).

25%

27%

ENM034

Change occurs in the inherited characteristics of a population of organisms over time because of the use or disuse of a particular characteristic (Bishop & Anderson, 1990).

22%

18%

ENM033

Change to the characteristics of populations (i.e. the proportion of individuals in the population having certain traits) of organisms is always random, and is not influenced by the favorability of that change in a given environment (AAAS Project 2061, n.d.).

21%

14%

ENM029

Except for differences between males and females, and between young and old, all organisms of the same species look and act the same (AAAS Project 2061, n.d.).

17%

11%

ENM028

All individuals within a population of organisms are the same. Differences among them are trivial and unimportant. All members of a population are nearly identical (Greene, 1990; Passmore & Stewart 2004; Anderson et al. 2002; Shtulman, 2006).

17%

11%

ENM030

The internal chemistry, appearance, and behavior of a species do not change, even over long periods of time (AAAS Project 2061, n.d.).

13%

10%

ENM052

Changes to the environment cannot lead to changes in the traits of species living in that environment.

12%

9%

ENM035

Change occurs in the inherited characteristics of populations of organisms over time because organisms observe other more successful organisms and model their appearance or habits (AAAS Project 2061, n.d.).

10%

8%

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.