Invasive Species and Population Growth-Activity #1


Activity Description: 

Students listen to a 50-minute presentation on how invasive species can affect the population growth of a native species through disease (or disease transmission), competition, and predation.

They then set up a hands-on experiment examining factors affecting carrying capacity.


Students will understand that population growth of native species can be positive or negative, is affected by many different biotic and abiotic factors, and is often affected negatively by invasive species.  In the experiment, students gain understanding of limiting environmental factors and their effects on carrying capacity.

Educational Standards: 

National Science Education Life Science Standards

Grades 5-8: The number of organisms an ecosystem can support depends on the resources available and abiotic factors, such as quantity of light and water, range of temperatures, and soil composition. Given adequate biotic and abiotic resources and no disease or predators, populations (including humans) increase at rapid rates. Lack of resources and other factors, such as predation and climate, limit the growth of populations in specific niches in the ecosystem. 

National Science Education Inquiry Standards

Grades 5-8: Different kinds of questions suggest different kinds of scientific investigations. 

Some investigations involve observing and describing objects, organisms, or events; some involve collecting specimens; some involve experiments; some involve seeking more information; some involve discovery of new objects and phenomena; and some involve making models. 

Mathematics is important in all aspects of scientific inquiry. 

Science advances through legitimate skepticism. Asking questions and querying other scientists' explanations is part of scientific inquiry. Scientists evaluate the explanations proposed by other scientists by examining evidence, comparing evidence, identifying faulty reasoning, pointing out statements that go beyond the evidence, and suggesting alternative explanations for the same observations. 

Sunshine state standards

SC.7.L.17.3: Describe and investigate various limiting factors in the local ecosystem and their impact on native populations, including food, shelter, water, space, disease, parasitism, predation, and nesting sites. 

SC.7.N.1.1: Define a problem from the seventh grade curriculum, use appropriate reference materials to support scientific understanding, plan and carry out scientific investigation of various types, such as systematic observations or experiments, identify variables, collect and organize data, interpret data in charts, tables, and graphics, analyze information, make predictions, and defend conclusions. 

SC.7.N.1.2: Differentiate replication (by others) from repetition (multiple trials). 

SC.7.N.1.4: Identify test variables (independent variables) and outcome variables (dependent variables) in an experiment. 

Pre-Activity Prep: 

Download from 

Be sure to go over the text ahead of time, tweaking it as you need to for your audience. In addition, all three activities are included in the presentation, so be sure to remove the ones you do not wish to do. 

Download and make copies of the student handout “Manipulating the Carrying Capacity” from 

Doing the Activity: 

The activity can be found on Page 2 of the PDF linked below.

  • Fifteen 10oz. plastic colored cups (not clear), ten sandwich containers, five petri dish lids, construction paper, lab tape (or masking tape), markers, fertilizer mix, access to a window or a light source with a bulb made for growing plants, three gallons of spring water, magnifying glasses, rulers, and duckweed (Lemna minor). 
  • You can order Lemna minor online or you can go to an aquatic plant nursery or aquarium store and see if they will donate some to your class. You can also go to a pond and get it yourself. 
  • Mix one liter of spring water with two teaspoons of fertilizer mix to make the “nutrient water”. Be sure to label it. 
  • Build a light bank with a shop light and two grow plant bulbs. Ideas for how to build one can be found here
Approximately 4 class periods and 4 weeks for experiment