Students who demonstrate understanding can: Construct an explanation based on evidence that describes how genetic variations of traits in a population increase some individuals' probability of surviving and reproducing in a specific environment.
Clarification statement: Emphasis is on using simple probability statements and proportional reasoning to construct explanations.
Official wording from the Next Generation Science Standards (NGSS Lead States, 2013). NGSS is a registered trademark of WestEd. Neither WestEd nor the lead states and partners that developed the NGSS were involved in the production of this page, and they do not endorse it. View on nextgenscience.org
No two rabbits in a population are exactly alike. Some have slightly thicker fur, some run a little faster, some have coats that blend better with the ground. Much of this variation is inherited. In a particular environment, certain variations give an individual a better chance of surviving long enough to reproduce, and so a better chance of passing those traits to offspring.
Students construct explanations based on evidence using simple probability and proportional reasoning. Suppose 80 percent of light-colored mice on dark lava rock are caught by owls, but only 30 percent of dark mice are. A dark mouse there has a much higher probability of surviving to breed. The trait does not guarantee survival; it shifts the odds.
This is the core of natural selection at the level of individuals. The environment does not create the useful variations, it acts on the variety that already exists, and which trait is helpful depends on the setting: dark fur helps on dark rock but hurts on pale sand.
Individuals cannot grow new inherited traits on demand. Variation already exists in the population, and the environment favors some variants over others.
'Fittest' means best suited to a particular environment, such as being well camouflaged, not necessarily strongest or largest.
A favorable trait raises the probability of survival and reproduction, but chance events still affect which individuals live.
On dark lava rock, 100 light mice and 100 dark mice are observed for a season. Owls catch 80 light mice and 30 dark mice. Compare the survival probabilities and explain the result.
Answer: Dark mice survived at 70 percent and light mice at 20 percent, so dark fur raises the probability of survival on dark rock by 3.5 times.
A bead or paper-dot 'predation' simulation on different colored backgrounds generates survival data students can turn into percentages. Changing the background and repeating shows that the favored trait depends on the environment.
The clarification statement stresses simple probability and proportional reasoning, so ask students to express every result as a fraction or percentage and compare rates rather than raw counts.
Original questions written for this standard. Choose an option or type your answer, then press Check. Every question has a worked explanation.
Answer: B) Brown beetles are more likely to survive and reproduce
Brown beetles are better camouflaged, so they have a higher chance of surviving.
Answer: 80 (also accepted: 80%, 80 percent)
40 out of 50 is 0.8, which is 80 percent.
Answer: D) Best suited to survive and reproduce in a particular environment
Fitness is about surviving and reproducing in a given environment.
Answer: A) Inherited genetic differences
Most variation is inherited, and new variations arise from random mutations.
Answer: B) They might be less likely to survive
Whether a trait helps depends on the environment; thick fur can cause overheating in heat.
Answer: variation (also accepted: variations, genetic variation)
Variation is the difference in traits among individuals.
Construct an explanation based on evidence that the process of evolution primarily results from four factors: (1) the potential for a species to increase in number, (2) the heritable genetic variation of individuals in a species due to mutation and sexual reproduction, (3) competition for limited resources, and (4) the proliferation of those organisms that are better able to survive and reproduce in the environment.
A full lesson with slides, activities and an exit ticket on variation and survival, pitched to grades 6-8 and editable in PowerPoint or Google Slides.
Make a lesson βA printable, differentiated worksheet on MS-LS4-4 with an answer key, ready in about a minute.
Make a worksheet βTurn variation and survival into a quiz students answer online that marks itself, with a class summary for you.
Build a test βSimple probability statements and proportional reasoning, such as comparing survival percentages for individuals with different traits.
MS-LS4-4 explains why individuals with certain variations survive more often; MS-LS4-6 uses math to show how that changes trait frequencies in a population over time.