are 90% of all animals...

Are 90% of All AnimalsInvertebrates?

During our study of classification, we have been defining livingand nonliving things and dividing all life into its five kingdoms.Now that we have observed vertebrates and invertebrates anddefined which animals would fall in which category, it is time toexplore an ecosystem and answer the question, “Are 90% of allanimals invertebrates?” We will be using the local ecosystem ofour brook to investigate our question.

First, think about your hypothesis and write the procedures youwill use to collect data. You will spend 1 to 2 class periodsobserving macroscopic animals in the ecosystem and collectingsome 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 theclassroom. Using a microscope, you can then observe andrecord any microscopic life in the water. You will then review allof your data to write your conclusions.

1 of 22Are 90% of All Animals Invertebrates?

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Are 90% of All Animals Invertebrates?

Suggested Grade Span

6–8

Task

During our study of classification, we have been defining living and nonliving things and dividingall life into its five kingdoms. Now that we have observed vertebrates and invertebrates anddefined which animals would fall in which category, it is time to explore an ecosystem andanswer the question, “Are 90% of all animals invertebrates?” We will be using the localecosystem of our brook to investigate our question.

First, think about your hypothesis and write the procedures you will use to collect data. You willspend 1 to 2 class periods observing macroscopic animals in the ecosystem and collectingsome invertebrates to observe more closely. Be sure to record, with drawings, the differentspecies observed by your group.

We will also collect water samples to bring back to the classroom. Using a microscope, you canthen observe and record any microscopic life in the water. You will then review all of your datato write your conclusions.

Big Ideas and Unifying Concepts

InterdependenceOrder and organizationSystems

Life Science Concepts

Populations and ecosystemsStructure and function

Design Technology Concept

Use of tools (microscopes)

Mathematics Concepts

Data collection, organization and analysisPercentsStatistics



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 andnonliving things. Next, we divided all life into its five kingdoms. Then we began to classify thekingdom that most students believed they knew the most about: animals.

The first categories I introduced were vertebrates and invertebrates. We spent some class timeobserving vertebrates and invertebrates and defined which animals would fall in whichcategory. 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 thatthey thought it was that 90% of the kinds (species) of animals were invertebrates. Some saidthat 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 chosethe brook that runs by our school for our investigation. This task could be accomplished byexploring other ecosystems (depending on what’s available in your area) when taking a field tripor when studying different biomes.

What This Task Accomplishes

Students reinforce and expand their knowledge of vertebrates and invertebrates. They will alsoreinforce their knowledge of the different phyla and classes of animals. By designing anexperiment to prove or disprove the statement in question, students will apply the scientificmethod during a field study. Students will use microscopes to observe microscopic animals (orto 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 andwrite the procedures they will use. Students will spend one to two class periods observingmacroscopic animals in a specific area in the chosen ecosystem. If appropriate, students willcollect these animals (particularly invertebrates and, in the stream, amphibians and fish) toobserve more closely. Students will record, with drawings, the different species they observedwith their classmates.

With the help of parent volunteers, I divided my class into two groups. With a larger class, Irecommend three groups. With smaller groups, students are able to record all of the speciesfound within that group. We collected for three-fifths of the time in the field and recorded resultsfor 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.



We determined which was plant and which was animal with our knowledge of plants andanimals. (Was it moving?) We discussed what was animal and what was protozoa. (Did it havemore than one cell?) With the help of stream guides, we further studied whether what we sawwere 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 studentswrote it for homework.

Interdisciplinary Links and Extensions

ScienceAfter each group records all of the species found within the assigned area for that group, classdata could be created by sharing information by these groups to ensure more accurate resultsand to verify data.

MathematicsStudents could calculate percentages of each species found and represent the data with avariety of tables, charts and graphs. Students could estimate population growth over a specificperiod 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 toconvert fractions to percents. Ask the students what they think about this statement: Does theauthor mean that 90% of all animals are invertebrates or that 90% of all species areinvertebrates?

As students begin to design their field studies, remind them that some invertebrates aremicroscopic and show students pictures of these invertebrates. Review collection guidelinesand how to use field guides for identification. I remind students that when we are collectingspecimens, we are collecting creatures from their habitats (homes). We are their guests andneed 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 haveenough water and space to move about. The keeper soon finds out that his/her job is to alsoalert the other collectors when one creature is eating another! The keeper needs to make surethat either the one is not eaten or that the prey is at least recorded on someone’s paper beforeit is eaten.

Encourage students to find animals by getting out there yourself. You can model patience byshowing students how to look for animals moving under the rocks. Usually the need forpatience takes care of itself, as the more-patient students go to the calmer areas and find allsorts of interesting organisms. Make sure that you leave enough time at the end of a collectionperiod for students to record the information collected.



You may find that bringing the critters inside brings more depth to the scientific drawings. I havedone this lesson both ways and find that if I have the students draw outside, it eliminates thetime consumed bringing the critters in and out of the building. Choose where you want to do thisaccordingly.

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 fivegroups of vertebrates. After they have responded with the list of mammals, reptiles, birds, fishand amphibians, ask, “Is this one a bird? a mammal?” etc., until they have discovered theirerror. 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 organismscarefully. You might explain that if they had time, it would be most appropriate to return each tothe exact location they found it. As this is not completely necessary, have the studentsrespectfully 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 thatwere 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 assmall larvae, to ensure that students record only animals, not plants or other microscopicorganisms.

While students are observing these animals, remind them that they are sampling a small portionof the brook. Encourage students to view what other students have and record their results asthey did out in the brook. While they record their results, remind students to be particular withtheir drawings – providing labels and details.

When they have finished observing and recording their results, return the microscopicorganisms to the brook as respectfully as they did the macroscopic organisms. Then havestudents calculate their results.

I first had students classify by labeling which organisms are vertebrates and which are notvertebrates. We shared some of these results with the class to ensure that the definitions of



vertebrates and invertebrates were understood by all students. Then, have students create thefraction of the invertebrates to the total number of animals.

Have students calculate the percent that they found. (I have found that most students calculatethe total number of animals in each category as opposed to the number of species. If you wouldlike them to do otherwise, emphasize that at this point.) Encourage students to use thispercentage 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 thatthey have that relate to their findings.

Concepts to be Assessed

(Unifying concepts/big ideas and science concepts to be assessed using the ScienceExemplars Rubric under the criterion: Science Concepts and Related Content.)

Design Technology – Use of Tools: Students observe that tools extend the ability of people tomake things, to move things, to shape materials and to examine things.

Life Science – Structure and Function; Populations and Ecosystems: Students identifycharacteristics of organisms and categorize living organisms as vertebrates and invertebrates.Students use the terms vertebrates, invertebrates, microscopic, macroscopic, organisms andanimals appropriately.

Scientific Method: Students describe cause-effect relationships with some justification, usingdata 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 misconceptionsand raising new questions.



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 modifyexplanations 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 andEcosystems: Students describe and group animals as vertebrates/invertebrates. Studentsunderstand 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 seeingcritters), cups for stream collection (yogurt containers work fine), nets for ponds, and othercollection 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 handlenses for recording organisms too small to define otherwise. Field guides are useful foridentification and labeling. I also created a recording sheet.

Possible Solutions

The student’s solution should show diagrams of all animals observed, with organisms correctlylabeled “vertebrate” or “invertebrate.” All organisms recorded should be animals, and thereshould be an appropriate number of recordings for the amount of time spent in the field. Thenumbers of the different organisms should also be recorded. Percents should be calculatedcorrectly. The hypothesis should relate to the question tested and to the student’s priorknowledge. Procedures should be clear enough to provide evidence about how the studenttested 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 knowledgeabout vertebrates and invertebrates. The original question should be reflected upon in thestudent’s conclusion. The conclusion should use the percentage to support or refute his/herhypothesis, but the student may not reflect why his/her information has done this. The studentshould correctly identify a relationship between vertebrates and invertebrates. The studentshould give a reasonable explanation of how the hypothesis was right or wrong, with supportingevidence from the data.

Teachers will need to assess this activity both on the findings the students record and onobservations of how the students use the microscopes.



Task-Specific Assessment Notes

NoviceThis student’s drawings are vague and missing labels for invertebrates/vertebrates, or thelabels are incorrect. There are only a few drawings; no other data are recorded withdrawings.The hypothesis is limited to a yes or no statement and gives no indication of priorknowledge. Procedures are sketchy at best. There is no clear evidence about how the studenttests 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. Thestudent does not use microscopes appropriately. There is no explanation of data.

ApprenticeThis student’s solution is complete in that s/he calculates the percent of invertebrates that s/hefound. There is no evidence of prior knowledge or extended thinking in either the hypothesis orin 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 studentcorrectly labels vertebrates and invertebrates but is unable to connect this with the leadingquestion. Other notations are recorded about where animals were found. The procedures aretoo 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 issome attempt to connect the findings to the hypothesis, but this student may only take intoaccount what s/he found and not what was found by other members in the class. The sample isvery small. The student is able to state some aspects of the data gathered but is unable toclearly articulate a trend or connection between the data and the hypothesis. The studentattempts to use the microscopes but may rush and not take the time to look for the microscopicorganisms found in the water. The student is unable to observe any vertebrates, possiblybecause s/he does not recall that this includes fish, reptiles and amphibians.

PractitionerThis 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. Thehypothesis relates to the question tested and to prior knowledge. Procedures are clear andmaterials are listed. The conclusion reflects the student’s hypothesis, the data collected andprior knowledge about vertebrates and invertebrates. The original question is reflected upon inthe student’s conclusion. An appropriate number of animals are recorded. Percents arecalculated 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 correctlyidentifies a relationship between vertebrates and invertebrates. The student gives a reasonableexplanation of how the hypothesis is right or wrong with supporting evidence from the data. Thestudent effectively uses microscopes to find microscopic life.

ExpertThis student’s solution is complete and detailed. The original statement, that 90% of all animalsare invertebrates, is used and related to the student’s findings. This student shows how s/he



calculated his/her percent. Prior knowledge is evident in the student’s hypothesis andconclusion. An appropriate number of organisms are collected. The drawings are clear and thenumber of organisms and measurements of size are recorded. The procedure is clear andshows thought about how to record an appropriate number of organisms for the task. There isclear evidence of scientific reasoning. Conclusions are supported by data and reflect data andprevious knowledge presented in the hypothesis. This student makes extensions in theconclusion by incorporating prior knowledge and asking questions that would lead to furtherexperimentation. There is evidence of extended thinking through questions raised andapplication of conceptual understanding about seasonal changes. The relationship betweenvertebrates and invertebrates is reflected in explanations and notations.



Novice



Apprentice



Practitioner



Expert



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