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Concepts/Objectives | Vocabulary/Background | Activity | Extension
T: How many trees ( or bushes or .....) are around our school (your neighborhood, park, etc.)?
T: If there are too many to count easily, how else could we find the answer?
T: Would we need to use some math?
Today we are going to talk about some of the tools that scientists use to study organisms. One of the most important tools that a scientist uses is Math. So today's activity will involve some addition and multiplication. Another tool that scientists use a lot is identification, finding out what something is, and categorization or putting things into similar groups. A third tool that a scientist might have to use is estimation. Let's say that you have a very large community area and you want to find out how many of a certain kind of organism live within the community. You could count all of the organisms in that area, but that would probably take a very long time (say the trees in our school area, park, or neighborhood). Or you could count the organisms in a smaller area within the community and then estimate (roughly figure) the total number in the whole community from that. (Teacher can do a simple diagram on board, draw large square with lots of 'x's for the trees. Then outline a smaller square within the big one. Have the students count the 'trees' in the small square and decide how many of those small squares it would take to fill up the big square and multiply by that number. Early elementary grades could use smaller quantities and practice addition.)
Next introduce the quadrat (a real one if available, or the coat hangar shaped into a square). This is one more tool that a scientist would use for this kind of study. It is a square of a known size or area (the area is the amount of space that is covered by the quadrat). This area can be calculated by multiplying the length of the quadrat by the width. A scientist would put this over an area of the community and count the organisms in it. Then she would estimate the number of these quadrats that would fit in the total community. Then, using multiplication (or larger groups of numbers and addition for pre-multiplication grades), we multiply the number of each organism by the number of quadrats.
So today we are going to study a make-believe community that has many different kinds of organisms.
What is a community? (Answers will vary: a neighborhood, ....Real answer: a group of living things that live in a certain area)
What is an organism? (Answers: a body with organs, .... Real answer: a term for any living thing)
(If grade appropriate:) What is a population? (Answers: a group of people, many animals...... Real answer: the group of a single species in a community)
We are going to identify some of the organisms in this community and then estimate their total number within the community.
- Divide into pairs or groups of 3.
- T: Pass out a plastic bag which contain a mixture of 12 bean soup and macaroni (be sure to have at least 8 different things in each bag) to each group. Also hand out Quadrat Craze Data Sheet. [Choose Data Sheet I (students not yet introduced to fractions) or II (students understand fractions).]
- Students spread the "community" of beans and pasta on a table or desk top. Two teams can work independently on the same 'community'.
- Students are to identify 8 categories of "organisms." It is up to the teams how they want to categorize the organisms; it can be done by: color, shape, pasta, beans or a combination of those. They can decide on real or made up names.
- Write this on the Quadrat Craze sheet. It has 4 columns: one for the name of the category, one for a description of what it is, the third column is for the number within the quadrat. (Ex: BB, black beans, 12)
- Estimate the total number within the community. Do this by counting how many quadrats would fit into the whole community (table top) and multiply that number by the number of 'organisms' in the category. Place this number in the last column of the sheet. This can be simplified for younger students by using a smaller number of categories, and a smaller area (desk top) for the total community (so it takes only 2 or 3 quadrats to cover the whole 'community') and then use addition.
- Have each team report on their 'findings'.
- Why are there differences between estimates of teams at same table? Different objects may have clustered together due to weight, texture, etc.
- How is this similar to differences in the natural world/wild? Animals and plants may group together because of better food sources, temperature, and other conditions.
- What are the problems of estimation? It is a rough 'guess' and not completely accurate.
- What are some of the problems using quadrats? You are only covering a certain area and the next area might be very different.
- Would scientists use just one quadrat count? No, (With older students discuss how) scientists would normally count several quadrats in an area and then calculate an average (appropriate to grade level: discuss averages)