Science Assessment ~ Ideas ~ There are similarities and differences between organisms living today, and between organisms living today and those that lived in the past, both within the same species and between species.

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.

Sub-Ideas
Items & Student Performance
Misconceptions
NGSS

Students are expected to know that:

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.
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.
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.
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.
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.
Natural selection acts on existing heritable variations that confer a reproductive advantage.
Natural selection requires variability, heritability, and reproductive advantage.
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.
Adaptation is a process by which populations become well-suited to their environments through natural selection acting on many traits over many generations.
An adaptive trait evolves when increasingly advantageous variants repeatedly arise and become more common in subsequent generations through natural selection.
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:

Students are not expected to know the many ways speciation can occur in a population.
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
EN034003	Some organisms survive and others die as the environment changes; this changes the proportion of organisms with certain traits in that population.	35%	50%
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 lizards with the traits that help them avoid the predator are more likely to survive and reproduce than the others.	32%	46%
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
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%
ENM026	Except for minor fluctuations from year to year, environmental conditions have stayed the same throughout the history of the earth (AAAS Project 2061, n.d.).	8%	7%
ENM047	Evolution happens when individual organisms acclimate or "get used to" new conditions gradually (Bishop & Anderson, 1990).	25%	27%
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%
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).	31%	27%
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%
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%
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%
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.).	16%	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).	16%	11%

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.

NGSS Statements
Code	Statement
LS4.C Grade 3	For any particular environment, some kinds of organisms survive well, some survive less well, and some cannot survive at all.
LS4.C HS	Natural selection leads to adaptation, that is, to a population dominated by organisms that are anatomically, behaviorally, and physiologically well suited to survive and reproduce in a specific environment. That is, the differential survival and reproduction of organisms in a population that have an advantageous heritable trait leads to an increase in the proportion of individuals in future generations that have the trait and to a decrease in the proportion of individuals that do not.
LS4.C MS	Adaptation by natural selection acting over generations is one important process by which species change over time in response to changes in environmental conditions. Traits that support successful survival and reproduction in the new environment become more common; those that do not become less common. Thus, the distribution of traits in a population changes.
LS4.C HS	Adaptation also means that the distribution of traits in a population can change when conditions change.
LS4.B HS	The traits that positively affect survival are more likely to be reproduced, and thus are more common in the population.
LS4.B HS	Natural selection occurs only if there is both (1) variation in the genetic information between organisms in a population and (2) variation in the expression of that genetic information--that is, trait variation--that leads to differences in performance among individuals.