HOW DOES YOUR GARDEN GROW?

Lesson 3:  Plant reproduction with seeds

Aim: What do all living things need to survive?

Do Now: Plants need water, light, proper temperatures, air and special chemicals to grow.   

Motivation: Display two potted geranium plants, Label each geranium plant A and B. Coat one leaf on plant labeled “B” top and bottom, with petroleum jelly.  Ask the class “What will happen to this leaf if I leave the petroleum jelly on it?” answer: The leaf will eventually die.  The children can estimate how many days it will take for the leaf to fall off. This lesson will explain control vs. variable in experimentation.

Discussion:

1.        The plants need to take in carbon dioxide and release oxygen.  Plants also need to release water, through its pores, during a process known as transpiration.  When the stomata  (The openings or tiny pores on the surface of the leaf) are blocked, the exchange of water and  gases cannot take place.  The leaf on the plant will die when its needs are not met.

The scientific method should be reviewed with the class (see below).  A plant that has already been treated with petroleum jelly five to seven days prior to the class could be shown to the students so that they can see the end result of this experiment.   

2.        Explain to the students how experiments can be conducted using one plant as a control and another plant as a variable. The control always stays the same.  Usually only one variable is tested during an experiment. Elicit from the class:  “What is the control in the geranium plant experiment? What is the variable?” answer: The control is the plant that remains unchanged (plant A) and the variable is the plant with the leaf that has the petroleum jelly on it, (plant B).  “If you wanted to try a different experiment on a plant, using some form of stimuli, what could you try?” Answer: You could place one plant in sunlight (control) and one plant in a closet  (variable). You could water the control plant and not the variable.  You could water the control plant and add water with fertilizer to the variable.  Any reasonable suggestions should be accepted.  Stress the importance of good record keeping during experimentation, using charts and journals to record all changes over a predetermined period of time. A wall chart for the classroom can be made using ClarisWorks, spreadsheet and graphs.  Daily observations of the variable should be recorded for seven days.

3.        All seed plants have vascular tissue (true roots, stems and leaves) and use seeds to reproduce. Examples of seed plants are oak trees used for lumber and making furniture and cotton plants used for making thread, material and clothing. Many fruits and vegetables contain seeds that are often eaten such as tomato and cucumbers.  Elicit from the class, “What are the names of other seed plants? ans. beans and eggplant, .  Name a fruit that has seeds that we do not eat.” Ans. watermelon, plums, oranges, pears, cherries and peppers.   Angiosperms are flowering plants that produce seeds within fruits. In a bean plant seeds are produced inside the bean pod. Avocados, cherries, plums, apples and peaches have pits in their centers. Gymnosperms have exposed or “naked” seeds. Most gymnosperms grow cones, pinecones are good examples of gymnosperms. Show the class examples of different fruits, cut open to expose the seeds.  Students can use a magnifying glass to examine the seeds closely. Break off some of the scales on the pinecones to expose the seeds and record findings.

Demonstration: Germination is the early growth of a plant from a seed.  There are three conditions needed for the growth of a plant from a seed, moisture, warmth and food. The children will practice thinking like a scientist by writing out the experiment in the scientific method, using a sequence of steps, (stating the problem, gathering information, developing a hypothesis, designing an experiment, controlling variables, interpreting data and stating a conclusion).  They can use a software writing program such as Microsoft word, when reporting the results of the scientific investigation.

 Students will work in a group and conduct an experiment with corn kernels.  Each team member will obtain a paper cup and write their name, the team name and the date.  Each person will place three cotton balls in each cup and three corn kernels on top of the cotton.  The cotton needs to stay wet at all times.  Water can be measured and then added to the cup for accuracy in control.   Two students will place their cup on the windowsill and water when necessary (the control) and two students will keep their cups away from sunlight (the variable). Other variables may be incorporated into the experiment but only one variable, per student in the group.  The team should form a hypothesis as to what will happen to the corn kernels.  For example will one corn kernel grow taller then the rest?  Will all kernels develop?  How many days will it take for some kind of change to occur? What factors will affect the development of the plant?   What will the students find at the end of the experiment?  The corn kernel will take about one week to germinate.  The group will compare their findings with each other to see if their hypothesis is correct.  After deciding which kernel (out of the three) demonstrated the most growth, they can make a chart comparing each of the four tallest plants in their group and/or the plant with the longest root to see which student had the tallest plant or longest root.  The data can be recorded on a graph using ClarisWorks.  Using the scientific method, each group will work together to write out all the steps of their experiment.  Note: This exercise is a good way to prepare for the annual event, The School Science Fair.

Summary:  Germination is the processes of growing plants from seed.  Seeds need three conditions for germination: food, water and correct temperature.

 Evaluation: Each group will communicate their results to the class, under the guidance of the teacher.  Their peers can question and challenge all aspects of the experiment and conclusion. The group will have the opportunity to defend their work. Peer assessment is a critical component of the new science standards.  It is an excellent evaluation tool for assessing achievement.

Performance standards: For reference see The Board of Education City of New York, Performance Standards in Science, first edition.  This lesson follows the new standards for learning in science.

Life Sciences Concepts: The students will ask questions about natural phenomena, objects and organisms, events and discoveries.  They will work individually and in teams to collect and share information and ideas. They will identify plant responses to environmental factors. The student will demonstrate scientific competence by completing a systematic observation and by using tools to gather data. They will share results with their peers. 

Homework: This assignment will help develop library and computer skills.  Using the internet, a current science magazine, the New York Times or any other resource write a one page report on “Frankenfoods” or genetically engineered food.

Materials: Paper cups, cotton balls, corn kernels, water, potted geranium plants, assorted fruit and pinecones and magnifying glasses, petroleum jelly.

Additional Links:

http://factmonster.com/spot/frankenfoods1.html, for background information about Bioengineered foods.  Please note that this information can be printed out if the Internet is not available for all students.

www.kids.infoplease.com, click on the following: (1)Homework Center 2)Writing Skills  3)Research Paper), this site will give you tips on writing reports.

Software: Microsoft Word, or any writing program can be used for recording the Scientific Method

ClarisWorks, for spreadsheet, charts and graphs.