
Description: 
In prior grades students learned to apply key concepts about ecosystems to understand the interactions among organisms and the nonliving environment. In grades 911 students learn about the factors that foster or limit growth of populations within ecosystems and that help to maintain the health of the ecosystem overall. Organisms participate in the cycles of matter and flow of energy to survive and reproduce. Given abundant resources, populations can increase at rapid rates. But living and nonliving factors limit growth, resulting in ecosystems that can remain stable for long periods of time. Understanding the factors that affect populations is important for many societal issues, from decisions about protecting endangered species to questions about how to meet the resource needs of civilization while maintaining the health and sustainability of Earth's ecosystems. 



Students are expected to:    Evaluate the conditions necessary for rapid population growth (e.g., given adequate living and nonliving resources and no disease or predators, populations of an organism increase at rapid rates).    Given ecosystem data, calculate the population density of an organism.*a  Mathematics Connections    *a A1.8.A Analyze a problem situation and represent it mathematically.    7.2.E Represent proportional relationships using graphs, tables, and equations, and make connections among the representations.    A1.3.B Represent a function with a symbolic expression, as a graph, in a table, and using words, and make connections among these representations.    A1.2.B Recognize the multiple uses of variables, determine all possible values of variables that satisfy prescribed conditions, and evaluate algebraic expressions that involve variables. 



