Are 90% of All Animals Invertebrates?

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1 Are 90% of All Animals Invertebrates? During our study of classification, we have been defining living and nonliving things and dividing all life into its five kingdoms. Now that we have observed vertebrates and invertebrates and defined which animals would fall in which category, it is time to explore an ecosystem and answer the question, Are 90% of all animals invertebrates? We will be using the local ecosystem of our brook to investigate our question. First, think about your hypothesis and write the procedures you will use to collect data. You will spend 1 to 2 class periods observing macroscopic animals in the ecosystem and collecting some invertebrates to observe more closely. Be sure to record, with drawings, the different species observed by your group. We will also collect water samples to bring back to the classroom. Using a microscope, you can then observe and record any microscopic life in the water. You will then review all of your data to write your conclusions. 1 of 22

2 Suggested Grade Span 6 8 Task During our study of classification, we have been defining living and nonliving things and dividing all life into its five kingdoms. Now that we have observed vertebrates and invertebrates and defined which animals would fall in which category, it is time to explore an ecosystem and answer the question, Are 90% of all animals invertebrates? We will be using the local ecosystem of our brook to investigate our question. First, think about your hypothesis and write the procedures you will use to collect data. You will spend 1 to 2 class periods observing macroscopic animals in the ecosystem and collecting some invertebrates to observe more closely. Be sure to record, with drawings, the different species observed by your group. We will also collect water samples to bring back to the classroom. Using a microscope, you can then observe and record any microscopic life in the water. You will then review all of your data to write your conclusions. Big Ideas and Unifying Concepts Interdependence Order and organization Systems Life Science Concepts Populations and ecosystems Structure and function Design Technology Concept Use of tools (microscopes) Mathematics Concepts Data collection, organization and analysis Percents Statistics 2 of 22

3 Time Required for the Task Three to four 45-minute class periods. Context We had been studying classification in our science class. First, we defined living things and nonliving things. Next, we divided all life into its five kingdoms. Then we began to classify the kingdom that most students believed they knew the most about: animals. The first categories I introduced were vertebrates and invertebrates. We spent some class time observing vertebrates and invertebrates and defined which animals would fall in which category. In our textbooks, there was the statement, Of all animals, 90% are invertebrates. During our discussion, I asked the students what that statement meant to them. Some said that they thought it was that 90% of the kinds (species) of animals were invertebrates. Some said that 90% of the numbers of animals were invertebrates. Some said that the statement was false. I suggested that we try to determine how true the statement was in one ecosystem. We chose the brook that runs by our school for our investigation. This task could be accomplished by exploring other ecosystems (depending on what s available in your area) when taking a field trip or when studying different biomes. What This Task Accomplishes Students reinforce and expand their knowledge of vertebrates and invertebrates. They will also reinforce their knowledge of the different phyla and classes of animals. By designing an experiment to prove or disprove the statement in question, students will apply the scientific method during a field study. Students will use microscopes to observe microscopic animals (or to observe animals too difficult to see without the aid of a microscope). How the Student Will Investigate First, discuss the statement with the students. Then, ask them to hypothesize the results and write the procedures they will use. Students will spend one to two class periods observing macroscopic animals in a specific area in the chosen ecosystem. If appropriate, students will collect these animals (particularly invertebrates and, in the stream, amphibians and fish) to observe more closely. Students will record, with drawings, the different species they observed with their classmates. With the help of parent volunteers, I divided my class into two groups. With a larger class, I recommend three groups. With smaller groups, students are able to record all of the species found within that group. We collected for three-fifths of the time in the field and recorded results for two-fifths of the time. We collected water samples to observe with the aid of a microscope. We spent two class periods observing microscopic life. 3 of 22

4 We determined which was plant and which was animal with our knowledge of plants and animals. (Was it moving?) We discussed what was animal and what was protozoa. (Did it have more than one cell?) With the help of stream guides, we further studied whether what we saw were animals. At the end of the final class period, we went over the experiment one last time. Students can write their conclusions either during a class period or for homework. My students wrote it for homework. Interdisciplinary Links and Extensions Science After each group records all of the species found within the assigned area for that group, class data could be created by sharing information by these groups to ensure more accurate results and to verify data. Mathematics Students could calculate percentages of each species found and represent the data with a variety of tables, charts and graphs. Students could estimate population growth over a specific period of time, given certain conditions (weather, pollution, etc.). Teaching Tips and Guiding Questions Discuss the question in depth before beginning the experiment. Review with students how to convert fractions to percents. Ask the students what they think about this statement: Does the author mean that 90% of all animals are invertebrates or that 90% of all species are invertebrates? As students begin to design their field studies, remind them that some invertebrates are microscopic and show students pictures of these invertebrates. Review collection guidelines and how to use field guides for identification. I remind students that when we are collecting specimens, we are collecting creatures from their habitats (homes). We are their guests and need to act accordingly. When in the field, model how to find and collect organisms. I have one person per site be the Keeper of the Creatures. That person s responsibility is to ensure that the animals have enough water and space to move about. The keeper soon finds out that his/her job is to also alert the other collectors when one creature is eating another! The keeper needs to make sure that either the one is not eaten or that the prey is at least recorded on someone s paper before it is eaten. Encourage students to find animals by getting out there yourself. You can model patience by showing students how to look for animals moving under the rocks. Usually the need for patience takes care of itself, as the more-patient students go to the calmer areas and find all sorts of interesting organisms. Make sure that you leave enough time at the end of a collection period for students to record the information collected. 4 of 22

5 You may find that bringing the critters inside brings more depth to the scientific drawings. I have done this lesson both ways and find that if I have the students draw outside, it eliminates the time consumed bringing the critters in and out of the building. Choose where you want to do this accordingly. While students are drawing, ask them: Which of these are vertebrates? How do you know? Can you use labels, shading and/or color to show patterns and details? If students think that the water strider, for example, is a vertebrate, ask them to list the five groups of vertebrates. After they have responded with the list of mammals, reptiles, birds, fish and amphibians, ask, Is this one a bird? a mammal? etc., until they have discovered their error. If they think it is a fish or a reptile, review with them the characteristics of that class. Once students have finished drawing the animals, remind them to return their organisms carefully. You might explain that if they had time, it would be most appropriate to return each to the exact location they found it. As this is not completely necessary, have the students respectfully return the organisms to the assigned area in which they found them. Remember to collect a sample of the water (or soil) to observe with microscopes/hand lenses. During the next class, explain to students that they are now going to observe the organisms that were less obvious in the stream. Review what an animal is and how to determine the differences between animals and plants: Does it move? Does it have chlorophyll? You can then review with the students the characteristics of microscopic animals, as well as small larvae, to ensure that students record only animals, not plants or other microscopic organisms. While students are observing these animals, remind them that they are sampling a small portion of the brook. Encourage students to view what other students have and record their results as they did out in the brook. While they record their results, remind students to be particular with their drawings providing labels and details. When they have finished observing and recording their results, return the microscopic organisms to the brook as respectfully as they did the macroscopic organisms. Then have students calculate their results. I first had students classify by labeling which organisms are vertebrates and which are not vertebrates. We shared some of these results with the class to ensure that the definitions of 5 of 22

6 vertebrates and invertebrates were understood by all students. Then, have students create the fraction of the invertebrates to the total number of animals. Have students calculate the percent that they found. (I have found that most students calculate the total number of animals in each category as opposed to the number of species. If you would like them to do otherwise, emphasize that at this point.) Encourage students to use this percentage and the results of their data to write their conclusions. Ask them: Do you think that your results could transfer to other ecosystems? Do you think this rule is true after your results? How do your results compare to another student s who observed animals in the same stream? After they have written their conclusions, I encourage students to think of other questions that they have that relate to their findings. Concepts to be Assessed (Unifying concepts/big ideas and science concepts to be assessed using the Science Exemplars Rubric under the criterion: Science Concepts and Related Content.) Design Technology Use of Tools: Students observe that tools extend the ability of people to make things, to move things, to shape materials and to examine things. Life Science Structure and Function; Populations and Ecosystems: Students identify characteristics of organisms and categorize living organisms as vertebrates and invertebrates. Students use the terms vertebrates, invertebrates, microscopic, macroscopic, organisms and animals appropriately. Scientific Method: Students describe cause-effect relationships with some justification, using data and prior knowledge. Mathematics: Students use numerical data, in describing events, answering questions, providing evidence for scientific explanations and challenging misconceptions. Students collect, organize and analyze data appropriately and use percents and statistics. Skills to be Developed (Science process skills to be assessed using the Science Exemplars Rubric under the criteria: Scientific Procedures and Reasoning Strategies and Scientific Communication Using Data.) Scientific Method: Observing, predicting/hypothesizing, collecting and recording data, manipulating tools, drawing conclusions, communicating findings, challenging misconceptions and raising new questions. 6 of 22

7 Other Science Standards and Concepts Addressed Scientific Method: Students describe, predict, investigate and explain phenomena. Scientific Theory: Students look for evidence that explains why things happen and modify explanations when new observations are made. The Designed World: Students observe that tools extend the ability of people to make things, to move things, to shape materials and to examine things. Life Science Structure and Function; Regulation and Behavior; Populations and Ecosystems: Students describe and group animals as vertebrates/invertebrates. Students understand that living things are found almost everywhere in the world and are interdependent. Scientific Tools: Students use microscopes to examine microscopic animals. Suggested Materials Students will need collection containers (flat, white-bottomed containers are easier for seeing critters), cups for stream collection (yogurt containers work fine), nets for ponds, and other collection tools for other ecosystems. Clipboards are excellent for recording results in the field. For the follow-up activities in the classroom and, if portable, for the field, microscopes and hand lenses for recording organisms too small to define otherwise. Field guides are useful for identification and labeling. I also created a recording sheet. Possible Solutions The student s solution should show diagrams of all animals observed, with organisms correctly labeled vertebrate or invertebrate. All organisms recorded should be animals, and there should be an appropriate number of recordings for the amount of time spent in the field. The numbers of the different organisms should also be recorded. Percents should be calculated correctly. The hypothesis should relate to the question tested and to the student s prior knowledge. Procedures should be clear enough to provide evidence about how the student tested the question. The student should effectively use microscopes to find microscopic life. The conclusion should reflect the student s hypothesis, the data collected and prior knowledge about vertebrates and invertebrates. The original question should be reflected upon in the student s conclusion. The conclusion should use the percentage to support or refute his/her hypothesis, but the student may not reflect why his/her information has done this. The student should correctly identify a relationship between vertebrates and invertebrates. The student should give a reasonable explanation of how the hypothesis was right or wrong, with supporting evidence from the data. Teachers will need to assess this activity both on the findings the students record and on observations of how the students use the microscopes. 7 of 22

8 Task-Specific Assessment Notes Novice This student s drawings are vague and missing labels for invertebrates/vertebrates, or the labels are incorrect. There are only a few drawings; no other data are recorded with drawings.the hypothesis is limited to a yes or no statement and gives no indication of prior knowledge. Procedures are sketchy at best. There is no clear evidence about how the student tests the statement. The percents may not be calculated or may be calculated incorrectly. Explanations do not show connection to data or to the student s original hypothesis. The student does not use microscopes appropriately. There is no explanation of data. Apprentice This student s solution is complete in that s/he calculates the percent of invertebrates that s/he found. There is no evidence of prior knowledge or extended thinking in either the hypothesis or in the solution. Either the statement is right or wrong, and s/he proves it one way or another. Drawings are clear and labeled, but there are too few organisms recorded. The student correctly labels vertebrates and invertebrates but is unable to connect this with the leading question. Other notations are recorded about where animals were found. The procedures are too vague to see evidence as to how the hypothesis can be tested. Some materials are listed. The explanation is incomplete, lacking the connection of the data to the hypothesis. There is some attempt to connect the findings to the hypothesis, but this student may only take into account what s/he found and not what was found by other members in the class. The sample is very small. The student is able to state some aspects of the data gathered but is unable to clearly articulate a trend or connection between the data and the hypothesis. The student attempts to use the microscopes but may rush and not take the time to look for the microscopic organisms found in the water. The student is unable to observe any vertebrates, possibly because s/he does not recall that this includes fish, reptiles and amphibians. Practitioner This student s solution is complete. The student has detailed diagrams of all animals observed. Numbers of the different organisms are recorded. Organisms are correctly labeled vertebrate or invertebrate. All organisms recorded are animals. All data are recorded accurately. The hypothesis relates to the question tested and to prior knowledge. Procedures are clear and materials are listed. The conclusion reflects the student s hypothesis, the data collected and prior knowledge about vertebrates and invertebrates. The original question is reflected upon in the student s conclusion. An appropriate number of animals are recorded. Percents are calculated correctly. The conclusion uses the percentage to support or refute the hypothesis, but the student may not reflect why his/her information has done this. The student correctly identifies a relationship between vertebrates and invertebrates. The student gives a reasonable explanation of how the hypothesis is right or wrong with supporting evidence from the data. The student effectively uses microscopes to find microscopic life. Expert This student s solution is complete and detailed. The original statement, that 90% of all animals are invertebrates, is used and related to the student s findings. This student shows how s/he 8 of 22

9 calculated his/her percent. Prior knowledge is evident in the student s hypothesis and conclusion. An appropriate number of organisms are collected. The drawings are clear and the number of organisms and measurements of size are recorded. The procedure is clear and shows thought about how to record an appropriate number of organisms for the task. There is clear evidence of scientific reasoning. Conclusions are supported by data and reflect data and previous knowledge presented in the hypothesis. This student makes extensions in the conclusion by incorporating prior knowledge and asking questions that would lead to further experimentation. There is evidence of extended thinking through questions raised and application of conceptual understanding about seasonal changes. The relationship between vertebrates and invertebrates is reflected in explanations and notations. 9 of 22

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