In this activity, students will:
- experience how selective predation is a form of natural selection.
- create and interpret predation data.
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Image Credit: seanmfreese
In this activity, students will unknowingly act as predators on candy. They will then discuss whether their predation was random or whether they had certain preferences. They will graph their results and determine how selective predation can impact a population and cause natural selection.
In this activity, students will:
In this (covert) activity, students will unknowingly act as predators on candy. They will then discuss whether their predation was random or whether they had certain preferences. They will graph the class results and determine how selective predation can impact a population and cause natural selection.
As you review the results as a class, consider introducing some of the scientific terms that are likely to come up in your unit on natural selection.
Selective predation is just one agent of natural selection, a process we'll be studying in this unit.
Either now or at the end of your unit, you can critique this demonstration to consider what it models well, and what it leaves out or disregards. For example, if you consider the five basic steps of natural selection using the VISTA acronym (Variation, Inheritance, Selection, Time, and Adaptation), you can see that candies demonstrate variation and are selected against, but are obviously not reproducing over subsequent generations to share genetic code, nor can they adapt. It may not be the appropriate time to dive into all of the mechanics of natural selection now, but you can set the stage.
Evolution is a two step process. First, there must be variation among individuals in a population. Secondly, natural selection acts on the phenotype, or the observable characteristics of an organism, such that individuals with favorable phenotypes are more likely to survive and reproduce than those with less favorable phenotypes. The genotype of the favorable phenotype, will increase in frequency over the following generations Some individuals are more fit in a particular environment and are thus able to pass on their genes to subsequent generations more successfully than other individuals. This process drives evolution within a population. Since it is crucial to both survive and reproduce in order to pass on genes to the next generation, natural selection results from both the differential survival and the differential reproductive abilities of individuals.
There are many forces that affect natural selection. For example, an organism’s environment can change, making some individuals more fit to survive or reproduce than others. Or, a predator can exert selective pressure on a population. Because predators do not capture their prey randomly, but often exhibit preferences, predation can change the composition of a prey’s population. Predator preference is thus an agent of natural selection.
This activity could serve as part of a much larger unit that aims to address the below standards.
Related Performance Expectations
Remember, performance expectations are not a set of instructional or assessment tasks. They are statements of what students should be able to do after instruction. This activity or unit is just one of many that could help prepare your students to perform the following hypothetical tasks that demonstrate their understanding:
MS-LS4-4.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.]
HS-LS4-3.Apply concepts of statistics and probability to support explanations that organisms with an advantageous heritable trait tend to increase in proportion to organisms lacking this trait. [Clarification Statement: Emphasis is on analyzing shifts in numerical distribution of traits and using these shifts as evidence to support explanations.] [Assessment Boundary: Assessment is limited to basic statistical and graphical analysis. Assessment does not include allele frequency calculations.]
Disciplinary Core Ideas
LS4B: Natural Selection
6-8: The traits that positively affect survival are more likely to be reproduced, and thus are more common in the population.
9-12: Natural selection leads to the predominance of certain traits in a population, and the suppression of others.
Science and Engineering Practice: Using Mathematics and Computational Thinking
6-8: Use mathematical representations to support scientific conclusions and design solutions.
Crosscutting Concept: Patterns
6-8: Graphs, charts, and images can be used to identify patterns in data.
9-12: Different patterns may be observed at each of the scales at which a system is studied and can provide evidence for causality in explanations of phenomena.
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