Describing Populations
What Happened to the Frogs?
Frogs are found on every continent except Antarctica, and they live in a variety of habitats around the world. You might even have heard them vocalizing to each other on a summer night. What factors do you think impact how large or small their populations are? How do environmental factors influence frog populations? What effects could other organisms have on frog populations?
Teacher Note
Use this video as a way to excite the students about the factors that impact populations. Make connections between how abiotic and biotic factors differ between biomes and how frog populations may be impacted by these factors naturally.
Populationglossary term (opens in a new window) ecologists study all of the factors that impact a population of plants or animals over time. Populations naturally increase and decrease in size depending on many factors. However, some populations fluctuate greatly year to year, and others change very little. What characteristics of speciesglossary term (opens in a new window) influence how their populations change over time? Think about how human activities impact plant and animal populations living alongside people. What are some ways human activities impact species in your state? Are the impacts positive or negative? What efforts are being made by state or local agencies to try to reduce negative impacts?
Ecologists strive to obtain long-term data sets when studying populations. A long-term data set can help an ecologist determine whether a population is declining because of natural or human-based causes. Imagine how different your interpretation of a population would be if you had one week versus 10 years of data to understand it. How would the change in data availability affect your results?
Explain Question
Explain the factors that impact squirrel populations.
Teacher Note
Use this student response to evaluate students’ prior knowledge of the concept. The Model Lesson provides information on common student misconceptions. This item should be completed on an individual basis.
Before You Begin
What do I already know about describing populations?
Teacher Note
This formative assessment item is intended to provide the teacher with feedback on prior knowledge of this topic. Students should have already learned about abiotic and biotic factors in elementary and middle school. Students could work in small groups to classify the factors and discuss their answers.
Teacher Note
This formative question could be used to assess a common misconception about populations. If the student does not select C as the correct answer, a discussion can begin about the factors that affect populations. If the student selects D as the correct answer, a brainstorming session about ways in which one population can affect another can begin. It would be best to start this as a think-pair-share activity and then discuss it further as a large group.
Teacher Note
This formative activity is intended to provide the teacher with feedback on prior knowledge of this topic and common sources of confusion when a student doesn’t understand the different levels of biological organization.
If students need review of these terms, they can do it now before moving onto more complex concepts. It would work well to have students do the question individually and then discuss the answers as a group. One way to extend this activity is to have students come up with examples of each of these terms.
Find out More About...
- human impacts on populations
- graphing populations
- differences between populations, ecosystems, and communities
Lesson Questions
- What are the factors of population demographicsglossary term (opens in a new window)?
- What is the difference between density-dependent and density-independent factorsglossary term (opens in a new window)?
- What are the differences between exponential and logistic growthglossary term (opens in a new window)?
- What is carrying capacityglossary term (opens in a new window) (K)?
- How are age structures created?
- What are the differences between type I, type II, and type III survivorship curves?
