Mercedes Diez

Mott Hall School

Summer Research Program at Columbia University - 1997

Investigating Space Requirement of Seed Plants

Background information

Seed plant, like all living things, have specific needs to survive and function properly, These needs include sunlight, water, minerals, living space, and carbon dioxide. [5-8 Content Standard C- Populations and ecosystems]

In this investigation you will study the effect limited living space has on the growth rate of individuals of a seed plant population.

Problem:

What is the effect of overpopulation on plants in a limited area? [5-8 Content Standard A- Identify questions that can be answered through scientific investigation]

Materials (per group)

16 bean seeds

3 flowerpots, each 5 cm in diameter

potting soil

graduated cylinder

metric ruler

labels

Procedure ( Have students write their procedure. [5-8 Content Standard A- Design and conduct scientific investigations] Make sure that they keep in mind the scientific method and that there is only one variable. Students will have different procedure but in a way very similar. an example of a procedure could be:

Fill each flowerpot with soil to within 2 cm of the top. Label each flowerpot with your name and the number 1, 2, or 3.

In container 1, plant one bean seed by pressing the seed into the soil about I cm deep.

In container 2, plant five seeds in set pattern.

In container 3, plant ten seeds in a set pattern.

Place all three containers in a well -lit area of the classroom. Water each container of seeds with 60 mL of water.

For the next two weeks, give each container 60 mL of water every two days. [Teaching Standard D- Structure time for extended investigations] Each day, measure the average height of the plants in each container. Record this information in the Data Table. Be sure to record your measurements to the nearest millimeter. You can calculate the average height of the plant for each container by adding the height of all the plants in the container and dividing this number by the number of the plants in the container. If a seed fails to germinate, or grow, give it a height of 0 for each reading. [Content Standard Unifying Concepts- Change, constancy, and measurement]

At the end of two weeks, plot the average height data from the Data Table on the Graph showing average height versus time. Use a different color of pencil or pen for each container’s graph. [5-8 Content Standard A- Use mathematics]

Observations:

Data Table

In which container do the plants show the greatest growth?

In which container the plant show the second greatest growth?

Analysis and Conclusions

Since all three containers contained approximately the same amount of soil and water, why was there a different in the growth of the plants in each container? [5-8 Content Standard A- Evidence and explanation]

If the plant in containers 2 and 3 were given enough water and nutrients for growth, do you think they would all grow up healthy in their container? Explain.

What is the variable in this investigation?

Why were the containers place in a well-lit area of the classroom?

Critical Thinking and Application

Why is it necessary to observe the plants a two - week period?

Suppose you repeated the investigation but this time you placed the bean into three 20.3 cm X 20.3 cm X 7 cm plant trays. What would happen?

Do you think animals have similar space requirement? If so, how might overcrowding affect animals? [Teaching Standard B- Orchestrate scientific discourse]

Assignment:

Observe how the amount of sunlight on plant leaves affects growth. Obtain three plants that are approximately 7 cm tall. Record their heights. Carefully clip off the necessary number of leaves on each plant so that each plant has the same number of leaves. On the first plant, cover half the leaves with aluminum foil. Cover all the leaves of the second plant with aluminum foil. On both plants, be sure to leave the stem and stalks exposed. The third plant will be the control. Each day record the height of each plant and the number of new leaves on each plant in a chart. At the end of the two weeks, graph the growth rate of each plant. [Content Standard Unifying Concepts- Change, constancy, and measurement] Explain your findings.

At the end of this experience "Investigating Space Requirement of Seed Plants" students will be able to understand density - dependent limiting factors. Another interesting experiment is the growth of duckweed in different conditions. These experiments, will help students understand that the density of the population is dependent on the limiting factors. The growths of many populations decrease as the density increases. The greater the density becomes, the more vigorously the limiting factors slows down population growth and then gradually the density approaches the carrying capacity of the environment. After density reaches the carrying capacity, birth and death rates become about equal; population growth levels off. [Content Standand Unifying Concepts- Equilibrium]

Another aspect that is important to population is density - independent limiting factors. The factor limiting the growth of a population is not related to population density. For example, temperature and oxygen supply are often related to physical aspects of the environment. Temperature frequently limits the size of the insect population. Throughout the summer the population size grows rapidly but in the fall, population size declines rapidly as adults die, thus the population declined before it reached the carrying capacity.

Population density is closely related to the spread of certain diseases. [5-8 Content Standard F- Populations, resources, and environments] For example, Malaria is a density - dependent factor because the denser the human population, the greater the chance of the disease being passed to others. The spread of Malaria is also dependent on the density of the mosquito population. In a dense population, disease can spread rapidly and kill many organisms in a matter of days.

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