Teaching the Local Water Cycle

Teaching about the water cycle can be made more realistic and valuable for students by incorporating what they know about water-where it comes from, what happens to it after they use it, and what problems are associated with its use. These materials, part of a unit called "The Broken Water Cycle", will help teachers facilitate place-based learning about water for upper elementary and middle school students.

Day 3: Biodiversity and Evolution

Objectives

Students will delineate how biodiversity relates to evolution

Lesson Overview

Students will discuss the importance of biodiversity, relate their knowledge of biodiversity to their background knowledge on evolution, and evaluate the role of invasive species on biodiversity.

Time: 
1 class period
Setting: 
Classroom
Materials

Images of endangered mammals (from below)

Procedure

Assignments: Students should read the appropriate textbook pages on Darwinian evolution and natural selection.

 

Engage: 5 minutes. Engage the students by showing them images of threatened or endangered mammals that represent global challenges to biodiversity: cheetah, polar bear, and Yangtze River dolphin.

Animal Info - Endangered Species website

 

Explore: 5 minutes. Question the students about why these animals might be going extinct. Once it is clear that habitat destruction leads to loss of animal diversity, ask why plant diversity and ecological diversity are important. Once it is clear that these concepts are all intricately related, ask why it matters that we retain animal and plant diversity.

Here is a list of the benefits of biodiversity

 

Explain: 20 minutes. Define evolution as change over time among populations. Continue to emphasize that individuals do not evolve, they adapt. Introduce the following concepts of evolution: natural selection and its dependence on the principles of variation, heritability, overproduction and reproductive advantage.

5 minutes. Have students think of one example of how trees meet the principles. Write student answers on the board. Have them then consider how each of these principles could be quantified. Then, lead them to understand that trees have tremendous variation, the phenotypes they pass on are heritable, they overproduce by making many seeds, and only some trees survive.

5 minutes. Answer questions or provide additional examples for the specific trees of the number of seeds they produce, the different species of each genus. There are more than 16 cultivars of red maple alone, and dozens of maple species.


Evaluate: 5 minutes. Perform a wrap-around activity where students discuss the relationship between biodiversity and evolution.  A wrap-around is a technique where one student is called on to answer a question, then another student supports or refutes her answer, and a third student summarizes. The third student then asks a question of another student to begin a subsequent wrap around. At random intervals, choose a new student to continue the discussion from where the other student left off.

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